Article

Fate of Salmonella during sesame seeds roasting and storage of tahini

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Abstract

Tahini is usually consumed without further heat treatment, and roasting of sesame seeds is the only Salmonella inactivation step in its traditional production process. This study examined the efficiency of the roasting process in the elimination of Salmonella from sesame seeds and the survival of Salmonella in tahini during storage. Sesame seed and tahini samples were inoculated with a cocktail of three serotypes of Salmonella (S. Typhimurium, S. Newport and S. Montevideo). Complete inactivation of Salmonella in sesame seeds, inoculated with 5.9log cfu/g, was achieved by roasting at 110°C for 60min, 130°C for 50min, or 150°C for 30min. Salmonella levels in tahini (aw=0.17) inoculated with 5.6log cfu/g and stored for 16weeks at 22 or 4°C decreased by 4.5 and 3.3 log, respectively. Results of this study demonstrated that the standard roasting process is sufficient to inactivate Salmonella in sesame seeds and low water activity of tahini prevents microbial growth, but its composition allows Salmonella to survive for at least 16weeks. Therefore, prevention of cross-contamination after roasting is crucial for food safety.

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... In that study, typical roasting temperatures of 110, 130, and 1508C were shown to destroy Salmonella. However, Torlak et al. (26) did not examine the survival of Salmonella during the entire manufacturing process; they focused solely on the survival of Salmonella during seed roasting and storage of tahini. Of particular concern may be the 24-h soaking period before dehulling and roasting of sesame seeds, which was not examined previously. ...
... The level of Salmonella after draining (before roasting) was determined to be~8.5 log CFU/g. This value was considerably higher than that achieved by Torlak et al. (26) before similar roasting experiments. When sesame seeds were drained for 1 h before roasting, seeds remained wet and had an a w of~1.0. ...
... However, only~2 log CFU/g was lost over the next 70-min period when the a w dropped below 0.4. By comparison, Unfortunately, Torlak et al. (26) did not report the actual changes in a w during roasting at each temperature examined; they only reported that the a w started at 0.98 and dropped to 0.14 within the first 10 min. The differences in the survival between the two studies may be attributed to use of a different inoculation level, differences in the rate of reduction of the a w during roasting, or the different Salmonella strains used. ...
Article
Tahini, a low-moisture food that is made from sesame seeds, has been implicated in outbreaks of salmonellosis. In this study, the fate of Salmonella was determined through an entire process for the manufacture of tahini, including a 24-h seed soaking period before roasting, subsequent grinding, and storage at refrigeration temperature. Salmonella populations increased by more than 3 log CFU/g during a 24-h soaking period, reaching more than 7 log CFU/g. Survival of Salmonella during roasting at three temperatures, 95, 110, and 130°C, was assessed using seeds on which Salmonella was grown. Salmonella survival was impacted both by temperature and the water activity (aw) at the beginning of the roasting period. When roasted at 130°C with a high initial aw (≥0.90) and starting Salmonella populations of ∼8.5 log CFU/g, populations quickly decreased below detection limits within the first 10 min. However, when the seeds were reduced to an aw of 0.45 before roasting at the same temperature, 3.5 log CFU/g remained on the seeds after 60 min. In subsequent storage studies, seeds were roasted at 130°C for 15 min before processing into tahini. For the storage studies, tahini was inoculated using two methods. The first method used seeds on which Salmonella was first grown before roasting. In the second method, Salmonella was inoculated into the tahini after manufacture. All tahini was stored for 119 days at 4°C. No change in Salmonella populations was recorded for tahini throughout the entire 119 days regardless of the inoculation method used. These combined results indicate the critical importance of aw during a roasting step during tahini manufacture. Salmonella that survive roasting will likely remain viable throughout the normal shelf life of tahini.
... Thus, every fifth ton of sesame seeds exported from India entered the EU food market, which made the EU a strategic trading partner. Sesame seeds, a rich source of lipids, fatty acids, endogenous antioxidants, proteins, carbohydrates, and minerals, are gaining in popularity as a raw ready to eat food [30,31], as well as a component ingredient of other foods, especially bakery products. Their important phyto-constituents are used in traditional and modern systems of medicine including wound healing, hepatic problems, memory disturbances, autoimmune encephalomyelitis, atherosclerosis, cancer, and hypertension [32]. ...
... Tahini is a high fat sesame paste produced from dehulled and roasted or unroasted sesame seeds. It is often used as an ingredient in other food products, for example, salad dressing, baba ghanoush, helva, and hummus [31,[33][34][35][36][37][38][39][40][41]. However, it is a product linked with recalls due to sesame seed contamination with Salmonella [30,31,[42][43][44], and there are multiple instances of Salmonella contamination. ...
... It is often used as an ingredient in other food products, for example, salad dressing, baba ghanoush, helva, and hummus [31,[33][34][35][36][37][38][39][40][41]. However, it is a product linked with recalls due to sesame seed contamination with Salmonella [30,31,[42][43][44], and there are multiple instances of Salmonella contamination. Indeed, some studies show tahini allows Salmonella to survive for at least 16 weeks [31]. ...
Article
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Sesame seeds within the European Union (EU) are classified as foods not of animal origin. Two food safety issues associated with sesame seeds have emerged in recent years, i.e., Salmonella contamination and the presence of ethylene oxide. Fumigation with ethylene oxide to reduce Salmonella in seeds and spices is not approved in the EU, so its presence in sesame seeds from India was a sentinel incident sparking multiple trans-European product recalls between 2020–2021. Following an interpretivist approach, this study utilises academic and grey sources including data from the EU Rapid Alert System for Food and Feed (RASFF) database to inform a critical appraisal of current EU foods not of animal origin legislation and associated governance structures and surveillance programs. This is of particular importance as consumers are encouraged towards plant-based diets. This study shows the importance of collaborative governance utilizing data from company testing and audits as well as official regulatory controls to define the depth and breadth of a given incident in Europe. The development of reflexive governance supported by the newest technology (e.g., blockchain) might be of value in public–private models of food safety governance. This study contributes to the literature on the adoption of risk-based food safety regulation and the associated hybrid public–private models of food safety governance where both regulators and private organizations play a vital role in assuring public health.
... Dehulling improves the color of tahini and masks the bitter taste by removing most of the oxalic acid and fiber found in the seed coats (Elleuch et al., 2014;Ereifej et al., 2005). Roasting of sesame seeds promotes the desired texture, color and flavor of the finished product (Akbulut and Oklar, 2008;Kahyaoglu and Kaya, 2006;Zahedi and Mazaheri-Tehrani, 2012), and inactivates pathogenic organisms (Torlak et al., 2013). Once roasted, the seeds are ground, mixed, cooled and filled in plastic bottles (QUALEB, 2015). ...
... The major intrinsic factors affecting behavior of pathogens in OL a w foods are the low a w and the presence of a high content of fat. Although OL a w food products do not support growth of foodborne pathogens, several studies reported the ability of major bacterial pathogens to survive in tahini (Al-Nabulsi et al., 2014Olaimat et al., 2017b;Osaili et al., 2020;Torlak et al., 2013), halva (Kotzekidou, 1998;Sengun et al., 2005;Osaili et al., 2017), peanut butter (Burnett et al., 2000;He et al., 2011;Kataoka et al., 2014;Kenney and Beuchat, 2004;Kilonzo-Nthenge et al., 2009;Park et al., 2008) and chocolate (Podolak et al., 2010;Tamminga et al., 1977) for long storage periods. ...
... have a characteristic ability to survive in these products for long periods. Torlak et al. (2013) found that a cocktail of three serotypes of Salmonella (S. Typhimurium, S. Newport and S. Montevideo) survived up to 16 weeks in tahini with an a w of 0.17 at 22 or 4°C with reductions of 4.5 and 3.3 log CFU/g, respectively. ...
Article
Oily, low water activity (OL aw) products including tahini (sesame seed paste), halva (tahini halva), peanut butter, and chocolate, have been recently linked to numerous foodborne illness outbreaks and recalls. This review discusses the ingredients used and processing of OL aw products with a view to provide greater understanding of the routes of their contamination with foodborne pathogens and factors influencing pathogen persistence in these foods. Adequate heat treatment during processing may eliminate bacterial pathogens from OL aw foods; however, post-processing contamination commonly occurs. Once these products are contaminated, their high fat and sugar content can enhance pathogen survival for long periods. The physiological basis and survival mechanisms used by pathogens in these products are comprehensively discussed here. Foodborne outbreaks and recalls linked to OL aw foods are summarized and it was observed that serotypes of Salmonella enterica were the predominant pathogens causing illnesses. Further, intervention strategies available to control foodborne pathogens such as thermal inactivation, use of natural antimicrobials, irradiation and hydrostatic pressure are assessed for their usefulness to achieve pathogen control and enhance the safety of OL aw foods. Sanitation, hygienic design of manufacturing facilities, good hygienic practices, and environmental monitoring of OL aw food industries were also discussed.
... The optimum roasting conditions to obtain the best texture and color of tahini ranges from 155 to 170 °C for 40 to 60 min (Kahyaoglu & Kaya, 2006). According to Torlak et al. (2013), Salmonella did not survive roasting of sesame seeds at 110, 130, and 150 °C. However, Zhang et al. (2017) reported survival of Salmonella on sesame seeds increased as a w decreased during roasting. ...
... However, Zhang et al. (2017) reported survival of Salmonella on sesame seeds increased as a w decreased during roasting. Thus, the presence of Salmonella in tahini might be due to the ability of Salmonella to survive the roasting process if the seeds are at a low a w at the beginning of the roasting process (Zhang et al., 2017), or their presence may be due to post-heat treatment contamination from equipment, workers or the processing environment (World Health Organization, 2008;Torlak et al., 2013). ...
... Kilonzo-Nthenge et al. (2009) reported that Salmonella and E. coli O157:H7 survived better in peanut butter stored at 25 °C than in that stored at 4 °C for the same period. Similarly, the number of Salmonella viable in a mixed culture decreased during 4 months storage of tahini at 4 and 22 °C by 3.3 and 4.5 log 10 CFU/g, respectively (Torlak et al., 2013). However, other reports revealed that Salmonella numbers in low a w products either did not change during storage or were not affected by storage temperature. ...
Article
Full-text available
Tahini (sesame seed paste) is a low water activity product that has been involved in several salmonellosis outbreaks. The objectives of the study were to examine over a year the impact of aw and storage temperature of tahini on the viability of Salmonella serovars previously stressed by drying or heat exposure. Tahini samples adjusted to aw values of 0.17, 0.35 and 0.50 were inoculated with a mixed culture containing 106-107 CFU/g of 4 serovars of unstressed, desiccation-or heat-stressed Salmonella and stored for up to 12 months at 10 and 25 °C. Generally, viability of stressed or unstressed Salmonella decreased as the storage temperature and time increased or the aw of tahini decreased. The survival of stressed or unstressed Salmonella in all samples decreased during storage for up to 12 months by ca. 6.0 and 3.3log10 CFU/g, respectively. Exposing Salmonella to heat stress had no significant effect on survival in tahini, while desiccation stress significantly decreased survival during storage, especially at 25 °C in low aw tahini.
... A study by Torlak et al. (2013) found that although Salmonella did not grow in tahini, it survived for 4 months at both room and refrigerator temperatures. The study also confirmed that the viability of Salmonella at 4°C was significantly higher compared to at 22°C (Torlak et al., 2013). ...
... A study by Torlak et al. (2013) found that although Salmonella did not grow in tahini, it survived for 4 months at both room and refrigerator temperatures. The study also confirmed that the viability of Salmonella at 4°C was significantly higher compared to at 22°C (Torlak et al., 2013). Foods with a high fat content and low water activity may even protect the Salmonella from inactivation (Podolak et al., 2010). ...
Article
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Abstract A widespread salmonellosis outbreak linked to consumption of hummus made from contaminated tahini imported from Turkey occurred in New Zealand in November 2012. This article summarizes the outbreak detection, investigation, and control. The New Zealand Enteric Reference Laboratory alerted public health units regarding a cluster of 11 persons with Salmonella Montevideo infection identified from different regions of the North Island of New Zealand. A multiagency outbreak investigation commenced to determine the source of illness and prevent further transmission. Salmonellosis is a notifiable disease in New Zealand. Outbreak cases were identified through routine salmonellosis notifications, and interviewed using a standardized questionnaire to identify common exposures. Clinical and food isolates were initially characterized by serotyping and then further typed by pulsed-field gel electrophoresis (PFGE). PFGE profiles were sent to PulseNet and international alerts were posted. The scope of the investigation widened to include persons with either Salmonella Maastricht and Salmonella Mbandaka infection following detection of these serotypes in tahini epidemiologically linked to laboratory-confirmed cases. All three of the tahini-associated serotypes were detected in people who had consumed tahini, and these were found to have PFGE profiles indistinguishable from the tahini isolates. Twenty-seven salmonellosis cases infected with at least one of the three tahini-associated Salmonella serotypes were detected between September 1 and December 31, 2012; of these, 16 (59%) cases (12 with Salmonella Montevideo, 3 with Salmonella Mbandaka, and 1 with Salmonella Maastricht infection) had PFGE patterns indistinguishable from the outbreak profile. The investigation led to a trade withdrawal and consumer recall for tahini sesame paste from the consignment and products containing this tahini. The outbreak ceased following the recall. The importer of the implicated tahini was reminded of his duties as a food importer, including ensuring appropriate product testing. Changes to New Zealand legislation strengthened food safety responsibilities of food importers.
... It has been found that Salmonella, Listeria innocua and E. coli O157:H7 were able to survive in tahini (Al-Nabulsi et al., 2014;Torlak, Sert, & Serin, 2013). Therefore, it is highly important to search for methods to control potential pathogens in Tahini. ...
... The reduction in S. aureus numbers in commercial tahini is due to the low water activity (a w ¼ 0.33) and high fat content (57% w/w), however, S. aureus is well adapted to survival in low water activity environments. Similar results were observed by Al-Nabulsi et al. (2014) and Torlak et al. (2013) who reported that different Salmonella serovars survived in commercial tahini. When tahini was diluted (a w ¼ 0.95), the numbers of S. aureus increased and this in agreement with previous studies which were done under the same experimental condition where S. Typhimurium, Listeria innocua and E. coli O157:H7 grew in hydrated tahini (Al-Nabulsi et al., 2013; 2014). ...
Article
Tahini (sesame paste) is a low-moisture ready-to-eat food that has been linked to foodborne outbreaks and recalls. The objectives of this study were to investigate the behavior of Staphylococcus aureus in commercial and hydrated tahini at 10, 21 and 37 °C and to inhibit S. aureus in these products by 0.1, 0.3 and 0.5% acetic or citric acid. S. aureus was able to survive in commercial tahini with reductions of 3.3, 1.6 and 0.7 log10 CFU/g at 37, 21 and 10 °C, respectively; while it grew in hydrated tahini with an increase of 3.9, 3.0 and 1.8 log10 CFU/ml at 37, 21 and 10 °C, respectively, by 28d. Citric or acetic acid at ≤ 0.5% reduced S. aureus in commercial tahini by ≤ 2.3 log10 CFU/ml by 28d compared to control at all of the tested temperatures. However, acetic and citric acid were more inhibitory at 37 and 10 °C, respectively. In hydrated tahini, viable S. aureus cells were not detected in the presence of 0.5 or 0.3% acetic acid after 7 and 14d, respectively, at both 21 and 37 °C; and after 14 and 28d, respectively at 10 °C. Acetic acid at 0.1% also reduced S. aureus numbers to undetectable levels after 14 and 28d at 21 and 37 °C, respectively. S. aureus cells were also not detected in the presence of 0.5% citric acid by 21d at all of the tested temperatures, or 0.1 and 0.3% citric acid by 28 and 21d, respectively at 21 °C. Acetic and citric acids could be used in tahini or tahini-based products to reduce the potential risk associated with S. aureus.
... The role of RpoS in the resistance to heat was extensively studied by various scientists. The increased heat resistance of the RpoS +ve strains was linked to heat-resistant proteins induced by the RpoS regulon under stress conditions (Dodd et al. 2002;Spector and Kenyon, 2012 Experimental conditions for inoculum preparation, as well as the method of inoculation or storage conditions are usually different from study to study (Uesugi et al., 2006, Komitopoulou andTorlak et al., 2013). Although low moisture foods cannot support microbial growth and are historically considered as 'low risk' in terms of pathogen contamination and no growth potential compared to high a w animal-or vegetable-derived products, they significantly contribute to the total number of food-borne infections and outbreaks (Chen, et al., 2009;Beuchat, et al., 2013). ...
... Most of the studies were conducted under different experimental conditions and therefore results are difficult to compare. The conditions of inoculum preparation (temperature, medium used) the method of inoculum preparation (centrifugation of broth growth or collection of cells from lawn plate), as well as the method of inoculation or storage conditions are usually different from study to study., or Blessington et al. have shown greater survival of Salmonella when cells were prepared using lawn plates while others,Torlak et al., 2013) prepared an inoculum using centrifuged broth growth.The ability of bacteria to survive in low moisture food at low storage temperatures is well documented. showed increased survival of various Salmonella strains in cocoa butter oil at lower temperatures, and Uesugi et al., (Uesugi et al., 2006) showed increased survival of Salmonella on almonds at low storage temperatures. ...
Thesis
This work investigated the survival and heat resistance of pathogens (Salmonella spp and Listeria monocytogenes) and a potential surrogate strain (E. faecium NRRL B-2354) in a selection of low moisture foods. The pathogens and the potential surrogate bacteria were inoculated into a selection of low moisture products (confectionery formulation, chicken meat powder, pet food and savoury seasoning, paprika powder and rice flour) and survival during storage as well as heat resistance were determined using glass vials and specially designed thermal cells. This study showed that pathogens can survive well in low moisture foods and survival was dependent on many factors such as water activity (a w), storage temperature and food composition. It was also shown that RpoS regulon plays an important role in Salmonella survival in low moisture foods. A strain lacking an active RpoS was significantly less viable in low moisture foods and significantly less heat resistant than the RpoS+ve strain. This study also showed that the use of E. faecium NRRL B-2354 as a surrogate is feasible for process validation although it has some limitations. It was shown that E. faecium NRRL B-2354 cannot be used as a surrogate in products containing high levels of sugar (confectionery powder) as Salmonella was significantly more heat resistant in this type of product than E. faecium NRRL B-2354. It was also shown that in paprika powder and in rice flour the two most resistant Salmonella strains (S. Enteritidis-PT 30 ATCC BAA-1045 and S. Typhimurium ST30; both RpoS +ve) in some conditions were more resistant than E. faecium NRRL B-2354. This study also showed that survival curves representing microbial survival during storage or during heat processes may not always be linear. In this study, concave upwards, concave downwards and linear curves were recorded and the Weibull model was used to fit raw data and precisely calculate the time required for 5 log reduction in viable numbers.
... These findings might reflect good hygienic practices of the sesame sample submitted to this research work. Torlak et al. [26] performed studies on matrices other than sesame seeds and concluded that the likely cause of the Salmonella outbreaks linked to sesame seed products was cross contamination of the products after the heat treatment. It was expected to find those pathogens in the raw samples as no heating step are involved in this process. ...
... neither E. coli were not found in these sesame seed samples even in high load of thermotolerants coliforms. According to [26] the standard roasting process is sufficient to inactivate Salmonella in sesame seeds. Indeed, raw sesame seed and sesame-based products are known to harbor sometimes Salmonella species. ...
Article
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Background Microbial contamination of edible low moisture food poses a significant public health risk for human. In this study, the microbial quality of sweet dehulled sesame seed croquettes, salted dehulled sesame seed and the raw sesame seed, sold under ambient conditions were examined. The samples were collected in the cities of Burkina Faso. The first type is sweet dehulled sesame seed croquettes (n 1 = 25); the second type is salted dehulled sesame seed (n 2 = 25) and the third type is raw sesame seed (n 3 = 25). Assessment of the microbial quality was based on the total aerobic mesophilic bacteria, the thermotolerant coliforms, the yeasts and moulds, the E. coli, and the Salmonella spp. using ISO methods. Results The results showed the presence of microorganisms varying from <1.0 to 1.72 × 10 ⁵ CFU g − 1 for thermotolerant coliforms, from <1.0 to 6,12 × 10 ⁶ CFU g − 1 for the total mesophilic aerobic flora and from <1.0 to 8.10 × 10 ⁵ CFU g − 1 for yeasts and moulds. The higher contaminations rates were mostly observed in raw sesame seed samples. No E coli or Salmonella pathogens were detected. Based on international standards of dehydrated food, 50.67% of the ready to eat sesame are satisficing while 17.33% are acceptable and 32% are not satisficing. Conclusion Attention should be emphasized on the processing practices, especially in crowded places where RTE sesames seeds are mostly sold. The high numbers of all microbial groups in these sesame seed samples suggested that the production of RTE sesame seed should be improved by better hygiene. This study highlights also that RTE sesame seed might harbor a wide range of microorganisms when processes are weak of hygiene.
... Generally, the production of tahini involves soaking, dehulling, roasting, and milling of sesame seeds [15] and the roasting treatment (110~150 • C for 30-60 min) is sufficient to inactivate most food pathogens [16]. However, some bacteria might survive at the roasting process due to the insufficient heating and the increase of thermal resistance of bacteria on sesame seeds with low water activity (a w ) [16,17]. ...
... Generally, the production of tahini involves soaking, dehulling, roasting, and milling of sesame seeds [15] and the roasting treatment (110~150 • C for 30-60 min) is sufficient to inactivate most food pathogens [16]. However, some bacteria might survive at the roasting process due to the insufficient heating and the increase of thermal resistance of bacteria on sesame seeds with low water activity (a w ) [16,17]. In addition, contamination might occur during the milling or packaging process after thermal treatment. ...
Article
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Tahini and tahini-based products are popular with consumers due to their special flavor and high nutritional values, but often have been linked to Salmonella outbreaks. The objective of this study was to compare effects of different kinds of natural antimicrobials on Salmonella inactivation in undiluted and diluted tahini during thermal treatment and storage. Results showed that the Weibull model was more suitable to describe the thermal inactivation behavior of S. montevideo CICC21588 in two kinds of tahini than the first-order model. Inactivation curves were concave-upward in undiluted tahini but concave-downward in diluted tahini. During storage of undiluted tahini, 3% oregano oil caused extra 1.44 or 0.80 log CFU/g reductions after 7 days at 25 °C or 4 °C compared to the control and 0.5% citric acid caused an extra reduction of 0.75 log CFU/g after 7 d at 4 °C. For diluted tahini, 2–3% oregano oil and 0.4–0.5% ε-polylysine reduced more populations compared to undiluted tahini. These antimicrobials all inhibited the growth of S. montevideo during 24 h at 25 °C and ε-polylysine had the best effect. Furthermore, these antimicrobials enhanced the Salmonella inactivation in diluted tahini during thermal treatment, and there was less of a synergistic effect of thermal and antimicrobials in undiluted tahini due to less sublethal injured cells caused by heat. This study may provide useful information for Salmonella inactivation in tahini.
... Regardless of the length of exposure to desiccation stress, concave downward curves (β > 1), with a first stage of slow inactivation followed by a sharp death phase, were verified for Salmonella during the blanched peanut kernel roasting (Fig. 3). On the other hand, other studies obtained concave upward inactivation curves using hot air treatment on unblanched peanuts and sesame seeds (Prestes, da Silva, Pereira, & do Nascimento, 2019;Torlak, Sert, & Serin, 2013), and oil roasting on almonds (Abd et al., 2012). Nevertheless, none of the mentioned studies have evaluated cells pre-adapted to desiccation. ...
... A higher thermal resistance of Salmonella non-adapted cells was verified on pecan halves, reduction of 1.2 log cfu.g −1 after 20 min at 120°C (Beauch & Mann, 2011). On the other hand, Torlak et al. (2013) reported reduction of 1.7 log cfu.g −1 of Salmonella inoculated in sesame seeds after 10 min at 110°C. Besides, the influence of the desiccation stress on heat resistance of Salmonella was also reported by Fong and Wang (2016) who evaluated the thermal resistance of five serotypes of Salmonella enterica pre-adapted to peanut oil (a w 0.52) for 6 d. ...
Article
The aim of this study was to evaluate the behavior of Salmonella Typhimurium ATCC 14028 during peanut dry roasting after pre-adaptation to desiccation stress. To cause desiccation stress, blanched peanut kernels (aw 0.43) were inoculated with S. Typhimurium and stored at 28 °C for up to 180 days. Then, the samples were roasted at 120 °C for 0, 10, 20 and 30 min. A concave upward curve for Salmonella population during the storage of blanched peanut kernels was observed, with reduction of up to 2.6 log cfu.g⁻¹. Further, the storage time had an impact on the thermal resistance of S. Typhimurium during the dry roasting process. The non-stored peanut sample showed reductions of 1.8 and 3.2 log cfu.g⁻¹, whereas in samples stored for 180 d the decrease in Salmonella count was 0.7 and 1.3 log cfu.g⁻¹ after 20 and 30 min at 120 °C, respectively. In addition, according to the Weibull model, to reach 4 and 5-log reductions between 34.9 and 59.0 min and 40.3 and 68.0 min in stored samples were needed. Therefore, these results showed an increase in the thermal resistance of S. Typhimurium, from 30 days storage time, on blanched peanut kernels suggesting the presence of cross-resistance.
... In the Middle East region, Tahini, which is produced from dehulled sesame seeds is used to prepare local foods such as salad and dessert (Abu-Jdayil et al., 2002;Razavi et al., 2007;Torlak et al., 2013). Tahini is rich in protein, lipids (especially omega-6 fatty acids), carbohydrates, thiamin, niacin, calcium, manganese and amino acid methionine (Al-Nabulsi et al., 2014;Torlak et al., 2013). ...
... In the Middle East region, Tahini, which is produced from dehulled sesame seeds is used to prepare local foods such as salad and dessert (Abu-Jdayil et al., 2002;Razavi et al., 2007;Torlak et al., 2013). Tahini is rich in protein, lipids (especially omega-6 fatty acids), carbohydrates, thiamin, niacin, calcium, manganese and amino acid methionine (Al-Nabulsi et al., 2014;Torlak et al., 2013). In addition, since Tahini is a natural product of sesame seed, it has antioxidant and anticancer properties and can stimulate liver function (Gharby et al., 2017) Tahini is consumed as a dessert at breakfast with grape molasses (Abu-Jdayil et al., 2002). ...
Article
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This study investigated the possibility of developing a novel functional sesame paste based dessert bearing probiotic bacteria (Lactobacillus paracasei and Bifidobacterium lactis). Probiotics viability in the dessert as well as pH, acidity, texture and microstructure modifications were investigated during 28 days of cold storage. Cell viability investigation showed that the medium preserved cell viability above 106 CFU/mL during cold storage. The pH and acidity of inoculated desserts have been modified through storage. Flow behavior and texture analysis showed that desserts inoculated with B. lactis showed higher yield stresses and creep elasticity, due to the exertion of polysaccharides by the bacteria. L. paracasei exhibited lower pH values and reduced the creep viscosity and elasticity, due to changes in molecular interactions. Microstructure analysis of the samples showed that the oil was in the form of emulsion and proteins were dispersed in the continuous aqueous phase. According to the results of this study, it is concluded that the exploitation of mixed cultures in the dessert formulation could guarantee acceptable probiotic viability and provide better texture attributes.
... They may also be dried through the application of hot air in mechanically agitated equipment. Other authors [32] report that the roasting of seeds, an operation applied in some situations, contributes to the control of microbial contamination in this type of food. However, very high temperatures can negatively affect the nutritional quality of edible seeds. ...
Article
In the present work, the microbiological quality of sesame, flaxseed, chia, pumpkin sunflower seeds, a mix of seeds, as well as flaxseed flour, marketed in southern Portugal, were studied through the counting of aerobic microorganisms at 30 °C (AM), molds and yeast (M&Y), Escherichia coli (β-glucuronidase positive) (β-GP E. coli), Staphylococcus coagulase positive, and detection of Salmonella spp. The persistence of AM and M&Y populations were also counted in organic and non-organic flaxseed at 20 °C for 11 months. The seeds with the highest average of AM were flaxseed (1,3 x 10⁶ CFU/g) followed by flaxseed flour (1,1 x 10⁶ CFU/g) while the lowest level was found in chia (2,9 x 10⁴ CFU/g). This seed also presented the lowest average values of filamentous fungi (9,8 x 10² CFU/g), whereas sunflower seeds had the highest levels (1,7 x 10⁵ CFU/g). Flaxseed flour had the highest yeast counts (1,5 x 10⁴ CFU/g). Although some samples had high levels of AM and fungi, β-GP E. coli and Salmonella were not detected, therefore, they complied with the microbiological criteria of the European Union. The organic flaxseed contained higher numbers of AM and M&Y than the non-organic ones (p < 0.05). In addition, the storage of flaxseed at 20 °C resulted in changes of AM and M&Y, showing that these populations were able to remain viable after eleven months (AM Log 5.4–Log 5.6; M&Y Log 2.8–Log 4.1). The results obtained in the present study, namely those high levels of AM and fungi (>10⁶ and 10⁴ CFU/g respectively), alert to the need of improving processing practices, storage/distribution conditions of edible seeds and derivatives, as well as the requirement of implementing adequate decontamination techniques.
... Aflatoxins B1, B2, G1 and G2 might be found in food and feed staffs and M1 and M2 are the metabolites of B1 and B2 in dairy products and can cause mutagenic, teratogenic and carcinogenic problems (Kollia et al., 2016;Somorin et al., 2016;Taye et al., 2016;Mi, 2014;Idris et al., 2013;Torlak et al., 2013;Yang et al., 2011;Idris et al., 2010;Brockmann et al., 2004;Chiou, 2002). In a study by Garrido et al. (2010) it was found that the incidence of aflatoxins M1 and M2 in dairy products exceeds the tolerable limit. ...
Article
Fungi grow everywhere in agricultural produce, food and surface of indoor and outdoor environment. The aim of this paper is to expand the growth and synthesis contributing factors and prevention mechanisms of fungi and its metabolites. Fungi, grouped as hydrophilic, mesophilic and xerophilic grow under a wider range of water activity, temperature, pH, gases and substrate. Besides the beneficial, the harmful fungi species are gaining attention due to their toxicity effect to consumer and economic losses. Taking into consideration of their prevalence, food group, daily intake, sampling, analytical techniques and consumer type’s regulatory limit have been established and promising prevention mechanisms discovered. Growth and production of toxic metabolites prevention includes good practices, use of plant extracts/probiotics, oxygen reactive scavenging substances, molecular silencing technology for a wide range of commodities. Nevertheless, application and commercialization of those techniques are limited.
... Bacteria do not generally survive in dry environments, but some are able to survive in a dormant state, and when conditions are suitable once again, they are active, as is the case for Salmonella. Similar studies found that Salmonella survived in tahini even after 16 weeks of storage [35]. Salmonella was also seen to survive in tahini up to 8 months [36]. ...
Article
Full-text available
The microbiological quality of tahini produced by several manufacturers in Lebanon was evaluated. Sixty-three tahini samples were collected randomly from retail markets throughout the country with production dates ranging from October 2015 to September 2017. The majority of the samples were from companies that are international exporters of the product. Nine of the obtained samples were from a traditional tahini manufacturer. All samples were assessed for the total Aerobic Plate Count, the presence and enumeration of Staphylococcus aureus, yeasts and molds,Salmonella, coliforms and Escherichia coli.Spread plate methods were used for detection and enumeration. The following results were obtained:the Aerobic Plate Count of the samples ranged between 1x10^2 CFU/g and 8.2x10^5 CFU/g with an average of 8.2x10^4 CFU/g. S. aureuscounts ranged between <20 CFU/g and 9.2x10^3 CFU/g with an average of 8.3x10^2 CFU/g. Yeasts and molds were present at counts ranging from <10 CFU/g to 2.2x10^5 CFU/g with an average of 2.5x10^4 CFU/g. Total coliform counts ranged between <30 CFU/g and 3.4x10^5 CFU/g with an average of 2.3x10^4 CFU/g. E. coli was present in ~37% of the samples (23 out of 63), while Salmonella was confirmed present in ~16% of the samples (10 out of 63). When compared with local and international standards, many of the samples showed unacceptable levels of microbial contamination. Certain impact factors were also determined when the samples were grouped according to their respective manufacturer, age, and processing method.
... In the present study, the number of bacterial cells in a cocktail of two serovars of Salmonella (S. typhimurium and S. abony) remained on the constant level in hummus during 60 days of refrigerated storage. It had been confirmed in other works, that Salmonella is able to survive for a long period in high fat-low moisture food products, such as hummus [24], tahini [3,25,26], halva [27] and peanut butter [28]. Although Salmonella cannot grow in these products, its ability to survive for a long period means that it represents a significant risk in high fat-low moisture food products. ...
Article
With the increasing demand for fresher, higher quality, minimally processed and safer food, there is a strong necessity to develop non-thermal processing techniques. Also for hummus, which is popular all around the world. In this work, the effect of refrigerated storage on the survival of pathogens in hummus treated by high hydrostatic pressure (HHP) (500 MPa/10 min/room temperature) was evaluated. The cocktail of two Salmonella, four Listeria monocytogenes and two Escherichia coli strains was used in this study. All pathogen types were able to survive in hummus during 60 days of refrigerated storage. HHP-treated samples plated on day 0 successfully achieved a > 5 log cfu/g reduction for all pathogen types. No residual survivors were present after 30 and 60 days in any of the HHP-treated samples. These results demonstrate that HHP may be a useful technique for the inactivation of pathogens and therefore helpful in designing non-thermal HHP conditions for pressurization of hummus.
... In most of the treatment evaluated a similar shape was observed between the curves of Salmonella inactivation (Fig. 1) and a w evolution (Fig. 2). This fact was also verified during sesame seed roasting (Torlak, Sert, & Serin, 2013). According to these authors increase in the heat resistance of the pathogen during the roasting can be explained by cell protein-water interactions. ...
Article
This study evaluated the efficiency of the dry and oil roasting processes in the inactivation of a pool of five serotypes of Salmonella isolated from the peanut supply chain (Miami, Muenster, Yoruba, Javiana and Glostrup). The Weibull model was fitted to the data to describe the thermal inactivation of Salmonella in peanut matrices. The time to achieve 5-log reduction of the pathogen during dry roasting at 125 °C was significantly different between the matrices (p < 0.05), being 1.5-fold more on the blanched peanuts than on the in-shell peanuts. Only the 145 and 160 °C protocols resulted in reductions > 5-log MPN/g of Salmonella for both matrices, with T 5d of 56 and 39 min for blanched peanuts and 46 and 44 min for in-shell peanuts, respectively. For the oil roasting, the Weibull model predicted the first decimal reduction after 7.2 s and 0.012 s at 115 °C and 145 °C, respectively. To achieve reduction of 5 log Salmonella it would take 3.0 min at 115 °C, and 0.40 min at 145 °C. The results demonstrated that temperature, heat process and in some cases the type of matrix influence the thermal resistance of Salmonella on peanuts.
... They explained that this is either caused by inadequate heat and/or duration practice during roasting or by post-roasting contamination. Torlak et al. [13] found that after injecting the Salmonella to the sesame seeds, the roasting process of sesame seeds which was realized under different temperatures (110, 130 and 150°C) and different time durations (30, 50 and 60 minutes) was effective to inactivate the Salmonella. ...
Article
Full-text available
A few studies in the literature reported that infections were developed due to the consumption of some halva products exported from Turkey. In this respect, this research aims to monitor and evaluate the microbiological risks originating from raw material in tahini halva production unit of a food company implementing ISO 22000. For this purpose, 12 different samples were taken from different sampling points in halva production processes and analyses have been performed. Results evaluated according to the decision tree method indicated that Salmonella spp. was present in sesame, and pistachio was unsuitable in terms of mould and yeast load. Sesame Roasting and Viscous Cooking steps were defined as critical control points as the temperature-time based treatments in these steps eliminate the microbiological risks arising from raw-materials. Furthermore, cocoa powder and pistachio raw-materials input validation operations were also defined as critical control points.
... They explained that this is either caused by inadequate heat and/or duration practice during roasting or by post-roasting contamination. Torlak et al. [13] found that after injecting the Salmonella to the sesame seeds, the roasting process of sesame seeds which was realized under different temperatures (110, 130 and 150°C) and different time durations (30, 50 and 60 minutes) was effective to inactivate the Salmonella. ...
Article
ABSTRACT A few studies in the literature reported that infections were developed due to the consumption of some halva products exported from Turkey. In this respect, this research aims to monitor and evaluate the microbiological risks originating from raw material in tahini halva production unit of a food company implementing ISO 22000. For this purpose, 12 different samples were taken from different sampling points in halva production processes and analyses have been performed. Results evaluated according to the decision tree method indicated that Salmonella spp. was present in sesame, and pistachio was unsuitable in terms of mould and yeast load. Sesame Roasting and Viscous Cooking steps were defined as critical control points as the temperature-time based treatments in these steps eliminate the microbiological risks arising from raw-materials. Furthermore, cocoa powder and pistachio raw-materials input validation operations were also defined as critical control points.
... Tahini processing includes soaking the dehulled sesame seeds in brine, roasting the seeds at 110e150 C for 30e60 min then milling (Torlak, Sert, & Serin, 2013;UNIDO, 2003). The temperature of tahini after milling roasted sesame seeds in traditional millers does not exceed 50 C (Osaili, Al-Nabulsi, Abubakar, Alaboudi, & Al-Holy, 2016); this temperature does not guarantee inactivation of microorganisms including E. coli O157:H7 if presented in the roasted seeds. ...
Article
Tahini, sesame seeds paste, is of great concern to both regulatory agencies and food processors as it may be exposed to microbial contamination through processing. This study aimed to evaluate the effect of gamma irradiation on inactivation of stressed E. coli O157:H7 and microbiota in tahini, and on the color and peroxide, p-anisidine, and acid values of tahini. Tahini samples were inoculated with a cocktail of 4 strains of unstressed or stressed (heat, cold, starvation, salt, acid, alkaline or ethanol stress) E. coli O157:H7 and exposed to gamma irradiation for up to 1.0 kGy. The D10-values of unstressed and stressed cells ranged from 0.31-0.39 kGy. Stresses (except for starvation) reduced the irradiation resistance of E. coli O157:H7 significantly (P < 0.05) in tahini. Irradiation dose of 1 kGy reduced inoculated E. coli O157:H7 and microbiota in tahini by 2.6–3.2 log10 CFU/g and 1.6 log10 CFU/g, respectively, and did not affect (P > 0.05) tahini quality (color and oxidative rancidity). Irradiation might be used as an effective means of eliminating E. coli O157:H7 and other foodborne pathogens with similar irradiation resistance, if present, in tahini in post-packaging situation without compromising the quality.
... The heat resistance of a particular strain of Salmonella may depend on the food matrix, which can be a very complex chemical system containing components such as protein and fats and may affect microbial thermal resistance (Bell and Kyriakides, 2002). For example, standard roasting processes are likely suitable to inactivate Salmonella in particulate foods, such as sesame, but the ground paste provides an environment that permits survival for at least 16 weeks (Torlak, Sert, and Serin, 2013). The addition of lipids to the heating medium can increase bacterial heat resistance (Kaur et al., 1998;Shachar and Yaron, 2006). ...
Chapter
This chapter describes heat resistance of Salmonella and other bacterial pathogens in low-moisture foods (LMF). It is well established that the thermal tolerance of microorganisms is enhanced as water activity decreases, thus presenting a unique challenge LMF. Thermal inactivation kinetic values are determined experimentally in the laboratory by conducting thermal death time (TDT) studies. Environmental stress has been shown to increase heat resistance. Aging of cultures creates stress on the organisms such that "late-log" or stationary-phase organisms have exhibited greater heat tolerance than cells in the "mid-log" growth or rapid growth log phase. The chapter shows a summary of culture conditions that impact heat resistance. The thermal resistance of bacterial pathogens increases as the water activity decreases in a LMF. The heat resistance of a particular strain of Salmonella may depend on the food matrix, which can be very complex chemical systems containing components such as protein and fats, which may affect microbial thermal resistance.
... In addition to notification 2017.0408, which pertains to this investigation, 18 notifications of Salmonella spp. in sesame paste, tahini or helva have been submitted to the RASFF portal. The frequent detection of Salmonella in sesame products recently motivated studies addressing the survival of Salmonella in tahini [19][20][21], and controls during the production process have been recommended [16]. Possible reasons for contamination, e.g. ...
Article
Full-text available
In spring 2016, Greece reported an outbreak caused by a previously undescribed Salmonellaenterica subsp. enterica serotype (antigenic formula 11:z41:e,n,z15) via the Epidemic Intelligence Information System for Food- and Waterborne Diseases and Zoonoses (EPIS-FWD), with epidemiological evidence for sesame products as presumptive vehicle. Subsequently, Germany, Czech Republic, Luxembourg and the United Kingdom (UK) reported infections with this novel serotype via EPIS-FWD. Concerned countries in collaboration with the European Centre for Disease Prevention and Control (ECDC) and European Food Safety Authority (EFSA) adopted a common outbreak case definition. An outbreak case was defined as a laboratory-confirmed notification of the novel Salmonella serotype. Between March 2016 and April 2017, 47 outbreak cases were notified (Greece: n = 22; Germany: n = 13; Czech Republic: n = 5; Luxembourg: n = 4; UK: n = 3). Whole genome sequencing revealed the very close genetic relatedness of isolates from all affected countries. Interviews focusing on sesame product consumption, suspicious food item testing and trace-back analysis following Salmonella spp. detection in food products identified a company in Greece where sesame seeds from different countries were processed. Through European collaboration, it was possible to identify and recall sesame spread as one contaminated food item serving as vehicle of infection and trace it back to its origin.
... Selective agar media were used for enumeration of Lactobacillus bacteria (MRS agar, Merck, Darmstadt, Germany), total aerobic bacteria (TSA agar, Merck, Darmstadt, Germany), Yeast and Mold (YGC agar, Merck, Darmstadt, Germany), Enterobacteriaceae (VRBD agar, Merck, Darmstadt, Germany), Coliform bacteria (VRBD agar, Merck, Darmstadt, Germany), and Clostridium perfringens (SIA agar, Merck, Darmstadt, Germany). The average number of colonies was multiplied by the reciprocal of the dilution factor and expressed as CFU/g of the content (Torlak et al. 2013;Menconi et al. 2014). ...
Article
Full-text available
This study was done to evaluate the effects of two dietary probiotic preparations (Bacillus subtilis and Bacillus licheniformis) on growth performance, intestinal microbiota, nutrient digestibility and cytokine gene expression in broiler chickens. A total of 180 male broiler chicks (one-day-old Ross 308 strain, average initial body weight = 40.05 ± 0.12) were used in a completely randomized design (CRD) composed of 3 treatments and 6 replicates. Experimental diets included: (1) basal diet (without additive), (2) basal diet plus 0.5 g/kg diet B. subtilis preparation (1 × 10⁹ CFU/g), (3) basal diet plus 0.5 g/kg diet B. licheniformis preparation (1 × 10⁹ CFU/g). The results showed that supplementation of B. licheniformis improved (P < 0.05) broilers’ body weight gain (BWG), feed conversion ratio (FCR), and production efficiency factor (PEF). Adding B. licheniformis caused the lowest (P < 0.01) feed cost per kilogram weight gain and the highest (P < 0.05) return of investment (ROI). Probiotic treatments significantly decreased (P < 0.01) ileal pH of the broilers. Probiotic treatments improved (P < 0.01) apparent metabolizable energy (AME) and total tract digestibility of protein. It was concluded that although both probiotic bacteria improved AME and total tract protein digestibility, B. licheniformis was superior to B. subtilis in improving broiler chickens’ BWG (2580.70 vs. 2427.45 g) and their PEF (418.95 vs. 374.49).
... Received 6 April 2019; Received in revised form 1 August 2019; Accepted 17 September 2019 products are consumed without further heat treatment, it is necessary to look for preservation methods to address post-process contamination. Several researchers investigated different methods for inactivation of foodborne pathogens in tahini or its products, like thermal inactivation (Torlak et al., 2013), use of acetic and citric acids (Al-Nabulsi et al., 2014;Olaimat et al., 2017) and gamma radiation (Osaili and Al-Nabulsi, 2016). However, among the available strategies to address the post-process contamination of tahini or its products and minimize the infection risk with foodborne pathogens, is the use of antimicrobial agents. ...
Article
Tahini is a popular food product in the Middle East region and is used as a major ingredient in several ready-to-eat food products. Tahini and its products have been linked to foodborne illness outbreaks and product recalls worldwide as a result of Salmonella spp. contamination. The objectives of the current study were to investigate: i) the effectiveness of 10 plant essential oil extracts on the viability of Salmonella spp. using disc diffusion ii) the antimicrobial activity of the most effective oils against Salmonella spp. in commercial or 10% w/v hydrated tahini (tahini-based product model) stored at 37, 25 and 10 °C for 28 d and iii) the effect of the addition of essential oil extracts on the sensory acceptability of tahini and hydrated tahini. Among the tested essential oils, thyme (TO) and cinnamon oil (CO) showed the highest antimicrobial activity against tested Salmonella spp. at 37 and 10 °C using a disc diffusion assay method. In tahini, the addition of 2.0% CO reduced the numbers of Salmonella spp. by 2.87, 2.64 or 2.35 log10 CFU/ml at 37, 25 or 10 °C, respectively, by 28 d. However, the antimicrobial activity of CO was more pronounced at all storage temperatures in hydrated tahini where no viable cells were detected after 3 d storage at 25 and 37 °C, or after 7 d at 10 °C. However, at 25 and 37 °C, the antimicrobial activity of CO was more evident since no viable cells were detected after 14 d when 0.5% was used. The numbers of Salmonella spp. were reduced by 3.29, 3.03 or 2.17 log10 CFU/ml at 37, 25 or 10 °C, respectively, after 28 d when 2.0% TO was added to tahini. Salmonella spp. were not detected in the hydrated tahini treated with 2.0% TO after 28 d at 37 °C or 25 °C, while at 10 °C, the numbers of Salmonella spp. were not significantly reduced after 28 d in hydrated tahini compared to the initial numbers at zero time. Therefore, the addition of TO and CO could be used to preclude the post process contamination of tahini with foodborne pathogens, yet, the addition of TO and CO to tahini reduced its consumer acceptability compared untreated tahini.
... Overall, it is not surprising that L. monocytogenes did not grow in this RTE dip, however a 1 log CFU/g population reduction was computed after only 20 days. Similar studies have assessed the fate of foodborne pathogen survival in tahini including E. coli O157:H7, S. enterica, and L. innocua (a surrogate for L. monocytogenes) [34][35][36]. Results determined that E. coli O157:H7 and L. innocua survived in tahini (pH 5.6, a w 0.31) during 28-day storage at 10, 21, and 37˚C, although populations of L. innocua decreased approximately 1-3 log CFU/g [34]. Although tahini may not be a favorable environment for L. monocytogenes for proliferation, using contaminated tahini as an ingredient in other refrigerated RTE dips with higher water activities (with the exception of baba ghanoush as determined in this study) may lead to the proliferation of this pathogen. ...
Article
Full-text available
Refrigerated ready-to-eat (RTE) dips often have pH and water activity combinations conducive to the proliferation of foodborne pathogens, including Listeria monocytogenes. This study conducted product assessments of five refrigerated RTE dips: baba ghanoush, guacamole, hummus, pesto, and tahini, along with individual dip components including avocado, basil, chickpeas, cilantro, eggplant, garlic, and jalapeno pepper. Dips and dip components were inoculated with 2 log CFU/g of L. monocytogenes and stored at 10°C for 28 days. The pathogen was enumerated throughout storage and growth rates were determined using the DMFit program to compute the time required for L. monocytogenes to achieve a 1 log CFU/g increase in population. Survival and growth rates varied significantly between the refrigerated RTE dips and dip components assessed in this study. For dips, L. monocytogenes progressively decreased in baba ghanoush, pesto, and tahini. In contrast, the pathogen proliferated in both hummus and guacamole and the highest growth rate was observed in guacamole (0.34±0.05 log CFU/g per day) resulting in a 1 log CFU/g increase in population in 7.8 days. L. monocytogenes proliferated in all dip components with the exception of eggplant and garlic. The pathogen achieved the highest growth rate in chickpeas (2.22±1.75 log CFU/g per day) resulting in a computed 1 log CFU/g increase in only 0.5 days. Results from this study can aid in understanding how L. monocytogenes behaves in refrigerated RTE dips and dip components and data can be utilized in understanding product formulations and in risk assessments.
... In a re port, Salmonella serotypes were inactivated at 120 °C for 30 mins and 110 °C for 40 mins, when inoculated at level of 6 log CFU/g in cocoa beans (Nascimento et al., 2012). Additionally, Torlak et al. (2013) showed that roasting pro cess conditions (110 to 150 °C for an hour) of sesame seeds when used in tahini manufacturing is sufficient to inactiva te 5 logs of Salmonella cells, but crosscontamination (e. g. personnel) should be prevented after roasting. As Salmo nella cells have been found to survive at least 16 weeks at 4 and 22 °C storage periods. ...
Article
Viral zoonosis tick-borne encephalitis (TBE) is usually transmitted to humans by the bite of an infected tick. Another possible way to become infected with the viral pathogen is through the consumption of raw milk and raw milk products. Based on the seroprevalence of antibodies against TBE viruses in goats in the Valais canton in a recently published study, a risk assessment for the viral contamination of goat milk was performed for this area. The probability of virus-contaminated milk was calculated to range between 0.0012% and 0.024% of household milk.
... In a report, Salmonella serotypes were inactivated at 120 °C for 30 mins and 110 °C for 40 mins, when inoculated at level of 6 log CFU/g in cocoa beans (Nascimento et al., 2012). Additionally, Torlak et al. (2013) showed that roasting process conditions (110 to 150 °C for an hour) of sesame seeds when used in tahini manufacturing is sufficient to inactivate 5 logs of Salmonella cells, but cross-contamination (e. g. personnel) should be prevented after roasting. As Salmonella cells have been found to survive at least 16 weeks at 4 and 22 °C storage periods. ...
... No data are available concerning the antimicrobial effect of sesame oil or sesamol against foodborne pathogens in meat or meat products. Even though, Torlak et al. (2013) inoculated a cocktail of three Salmonella enterica serotypes (S. Typhimurium, S. Newport and S. Montevideo) at an initial level of 5.6 log CFU/g into tahini (sesame seed paste) samples and observed a decrease by 3.3 and 4.5 logs during tahini storage at 4 and 22 • C for 16 weeks, respectively, where the Salmonella counts in this tahini declined to 2.3 and 1.1 log CFU/g, respectively. ...
Article
The antioxidant and antimicrobial effect of sesame oil (10, 30, and 50 g/kg) and sesamol (0.1, 0.3, and 0.5 g/kg) in meatballs during cold storage for 18 days at 3 ± 1 °C was investigated. Sesame oil and sesamol did not alter the sensory attributes of meatballs. Addition of either sesame oil or sesamol significantly delayed lipid oxidation when compared with control. Sesamol exhibited more potent antioxidant activities more than sesame oil. During storage, the aerobic plate counts (APCs) and Enterobacteriaceae counts (EBCs) were markedly (P < 0.01) decreased in meatballs treated with sesame oil or sesamol in comparison with untreated control samples. Control meatballs showed signs of quality deterioration at day 7 of storage, while treated meatballs exhibited longer shelf life to about 9–18 days according to sesame oil or sesamol concentrations. Both sesame oil and sesamol induced marked (P < 0.01) decline in E. coli O157:H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus and Listeria monocytogenes that artificially inoculated to meatballs. Sesamol was more effective than sesame oil in reduction of APC, EBC as well as foodborne pathogens. The results suggest that both sesame oil and sesamol are potentially useful natural additives to fresh meat products for improving its microbial quality and extend its shelf life during cold storage.
... The two positive batches of Brand C have their best before date in mid-2023. Some studies have shown that Salmonella can survive in sesame-based products for several months [2][3][4]. Moreover, the concerned products have a long shelf life and might still be stored in people's homes. ...
Technical Report
Full-text available
Since January 2019, 121 cases of Salmonella enterica infections with six different serotypes linked to sesame-based products have been reported in five EU/EEA countries. The serotypes are S. Amsterdam, S. Havana, S. Kintambo, S. Mbandaka, S. Orion, and S. Senftenberg. Case interviews in four countries revealed consumption of sesame-based products (halva or tahini) prior to illness. Almost half of the cases are in children ≤10 years, who also represent over half of hospitalised cases. No deaths have been reported. Since November 2019, 14 batches of sesame-based products originating from Syria, tested positive for one or multiple Salmonella outbreak strains (twelve from Brand A, two from Brand C). Based on available epidemiological, microbiological, and traceability information, the probable vehicles of infection are sesame-based products imported from Syria, at least in countries involved in the traceability of the positive batches. These products are sealed and ready to be consumed, suggesting that the contamination occurred before the products reached the European Union/European Economic Area (EU/EEA) market. The intermittent occurrence of human cases and the identification of positive food samples since 2019 indicate the availability of the contaminated sesame-based products on the EU/EEA market for over two years. This has posed a risk for human infections and severe clinical illness with several Salmonella serotypes, particularly among children. Control measures implemented since August 2020 on the involved batches of sesame-based products have not prevented the occurrence of human cases to date. Moreover, the concerned products have a long shelf life and might still be stored in people's homes. Considering the limited information on product manufacturing and distribution, there remains a risk for new Salmonella infections in the EU/EEA linked to imported sesame-based products from Syria.
... It promotes flavor, desired color and physicochemical changes [12,13,14] that increase overall palability of product. It improves microbiological safety, by destroying unwanted microorganisms, and inactivates enzymes that alter the product during storage [15]. Likewise, it improves digestibility, sensory quality and shelf life of food products; and it facilitates oil extraction by destroying cellular barriers and toxic heat-labile substances in nuts and seeds [16]. ...
Article
Due to its high content in linoleic acid, which is a polyunsaturated fatty acid, Citrullus lanatus oil is prone to oxidation. However, roasting generates Maillard reaction products having an antioxidant effect capable to preserve lipids against oxidation. Therefore, this study investigated the impact of roasting on C. lanatus kernels oil properties. The treatments consisted of roasted kernels in an oven at 180 °C for 20 min compared to unroasted kernels. Oil were extracted using a press coupled with a thermoregulator without heating (control), at 60 °C and 100 °C for unroasted kernels and without heating for those roasted. The chemical parameters, antioxidant capacity and oxidative stability of these oils were evaluated. The result showed that roasting did not significantly influence the pH of oils and the pH were acidulous (5.23 ± 0.00 to 5.50 ± 0.01). In addition, roasting increased oil acidity and peroxide value; while iodine and saponification values decreased. Roasting also increased the total phenol content, antioxidant capacity and oxidative stability of C lanatus kernels oil. Roasted kernels oil was of good quality and classified as "semi-drying or di-unsaturated oils" with the best resistance to auto-and thermo-oxidation. Our results suggest that roasting at 180°C for 20 min would extend the shelf life of C. lanatus kernels oil without compromising its quality.
... In addition, the doses and/or duration of treatments required to achieve suitable reductions in microbial hazard concentrations may negatively affect the sensory quality (e.g. taste and texture) and consumer acceptability of some LMF products (6,43,48,62). While it is critical that research into the efficacy and commercial application of hazard reduction interventions continues, due to the current difficulties in reliably reducing levels of microbial hazards on LMF products without unduly affecting their quality, primary emphasis in the industry should be placed on minimizing contamination during pre-harvest and preventing contamination during harvest and processing operations. ...
Article
Low-moisture foods (LMF) are increasingly implicated in outbreaks of foodborne illness, resulting in a significant public health burden. To inform the development of a new Codex Alimentarius code of hygienic practice for LMF, we applied a rapid knowledge synthesis and transfer approach to review global research on the burden of illness, prevalence, and interventions to control nine selected microbial hazards in eight categories of LMF. Knowledge synthesis methods included an integrated scoping review (search strategy, relevance screening and confirmation, and evidence mapping), systematic review (detailed data extraction), and meta-analysis of prevalence data. Knowledge transfer of the results was achieved through multiple reporting formats, including evidence summary cards. We identified 214 unique outbreaks and 204 prevalence and 126 intervention studies. Cereals and grains (n=142) and Salmonella (n=278) were the most commonly investigated LMF and microbial hazard categories, respectively. Salmonella was implicated in the most outbreaks (n = 96, 45%), several of which were large and widespread, resulting in the most hospitalizations (n = 895, 89%) and deaths (n = 14, 74%). Salmonella had a consistently low prevalence across all LMF categories (0 to 3%), but the prevalence of other hazards (e.g., Bacillus cereus) was highly variable. A variety of interventions were investigated in small challenge trials. Key knowledge gaps included underreporting of LMF outbreaks, limited reporting of microbial levels in prevalence studies, and a lack of intervention efficacy research under commercial conditions. Summary cards were a useful knowledge transfer format to inform complementary risk ranking activities. This review builds upon previous work in this area by synthesizing a broad range of evidence using a structured, transparent, and integrated approach to provide timely evidence informed inputs into international guidelines.
... While data on inactivation of foodborne pathogens on nuts are abundant, less is known about the efficacy of different inactivation methods for pathogens on seeds, grains, or spices. Dry roasting sesame seeds for 30 min at 130°C reduced Salmonella numbers by~5 log CFU/g (Torlak et al., 2013). Exposure to aerated steam for 90 s led to N 5 log reduction of E. coli O157:H7 and Salmonella Weltevreden on alfalfa and mung bean seeds (Studer et al., 2013). ...
Chapter
Worldwide nut production has expanded rapidly in recent years with a corresponding increase in consumption. Large outbreaks of salmonellosis have been associated with nuts and their products during this same time period, which has resulted in a major shift in the approach used to process these products. A brief overview of the history and use of nuts and differences in production and harvest practices of several major nuts are presented in this chapter. The association of foodborne pathogens with nuts is discussed in the context of outbreaks, recalls, and surveys. Potential routes of contamination of nuts with foodborne pathogens are presented along with an overview of current thermal and nonthermal methods for the reduction of pathogens and the factors affecting their efficacy.
Chapter
Heat-based processes have been used for centuries for food preservation and still remain the most widely used preservation technique in food manufacturing. However, thermal processing treatments are not as efficacious in the destruction of pathogenic microorganisms at low water activities compared to moist environments. Several dry-heat processes have been applied to low-moisture foods and include drying, hot air and baking, air impingement, dry roasting, and oil roasting. These applications require higher temperatures and longer heat times to obtain equivalent lethality to moist-heat processes. Moist-heat processes, which include blanching, moist-air impingement, and controlled condensation steam, are very effective at inactivating microorganisms because the added moisture significantly reduces microbial thermal resistance. However, an increased moisture content of the product can reduce the shelf life, often resulting in the necessity for the (energy consuming) re-drying of product to remove the added moisture. Lastly, extrusion has been shown to be an effective process for microbial inactivation.
Article
In combination with other strategies, hyperosmolarity and desiccation are frequently used by the food processing industry as a means to prevent bacterial proliferation, and particularly that of foodborne pathogens, in food products. However, it is increasingly observed that bacteria, including human pathogens, encode mechanisms to survive and withstand these stresses. This review provides an overview of the mechanisms employed by Salmonella spp., Shiga toxin producing E. coli, Cronobacter spp., Listeria monocytogenes and Campylobacter spp. to tolerate osmotic and desiccation stresses and identifies gaps in knowledge which need to be addressed to ensure the safety of low water activity and desiccated food products.
Article
Salmonella continues to be the leading cause of acute gastroenteritis and recently has been involved in infections related to edible seeds and their products, including tahini. This study investigated the (i) effectiveness of using gamma irradiation to inactivate starvation- and heat- or cold-stressed Salmonella in tahini, (ii) effect of storage on the sensitivity of stressed Salmonella to irradiation, and (iii) effect of irradiation on the chemical and physical characteristics of tahini. Tahini samples were inoculated with a cocktail of unstressed or stressed (starvation and heat or cold stress) Salmonella isolates and then exposed after storage at 21°C for 0, 7, and 30 days to gamma irradiation for up to 2.0 kGy. Additionally, the effect of irradiation on the color, peroxide, p-anisidine, and acid values of tahini were assessed. The initial level of unstressed and starvation- and heat-stressed Salmonella in tahini decreased by ca. 4.6 log CFU/g after exposure to 2.0 kGy, while cold-stressed cul...
Article
Unpasteurized ingredients, such as contaminated sesame seeds or flour, may introduce Salmonella into bakery products. Therefore, the use of a validated baking process is critical to eliminate this pathogen. This study compared the effect of oven relative humidity (RH) on the reduction of Salmonella and yeast during baking of inoculated bread dough topped with inoculated sesame seeds. Salmonella was injected into individual portions of bun dough to yield populations of 7.0-8.0 log CFU/g; dough was proofed and then topped with dry, inoculated sesame seeds (6.0-7.0 log CFU Salmonella/g seed). The seeded buns and seeds alone were baked in dry (average ~3% RH) or moist (average 20% RH after wet bulb spike) oven conditions for 7 and 9 min, respectively, to match a "bun-color standard," as suggested by a commercial bakery. After complete baking, Salmonella and yeast populations in the bun had decreased > 5-log for both methods. In contrast, differences in oven RH affected inactivation on the surface seeds, with reductions of 3.6 and > 6.0 log Salmonella at the end of dry and moist baking, respectively. This study demonstrates that maintaining an average 20% relative humidity during baking enhances the lethality on the product surface, compared to < 3% RH, while also maintaining quality.
Chapter
This chapter presents an overview of microbial ecology for nuts, seeds, sprouts, and their products in retail markets or food manufacturers. It discusses quantitative and qualitative approaches used to assess pathogenic bacterial contamination of nuts, seeds, and sprouts and also analyzes the published data about microbiological changes occurring in seeds and sprouts during production in a real manufacturing plant. Edible nuts were generally believed to contain few microorganisms due to their inherent dry characteristics, which provide unfavorable environments for bacterial survival and growth. Seeds used for sprouting can have significant levels of endemic bacteria. Contamination levels and the prevalence of bacteria in seeds used for sprout production. Edible nuts, seeds, and sprouts harbor considerable numbers of microorganisms, and the prevalence of food-borne pathogens has been reported in a number of publications. Molds and their toxic metabolites and food-borne pathogenic bacteria are a major concern for the food safety of edible nuts and seeds.
Article
Salmonellosis has been increasingly associated with contaminated spices. Identifying inoculation and stabilization methods for Salmonella on whole spices is important for development of validated inactivation processes. The objective of this study was to examine the effects of inoculation preparation on the recoverability of Salmonella enterica from dried whole peppercorns and cumin seeds. Whole black peppercorns and cumin seeds were inoculated with S. enterica using one dry transfer method and various wet inoculation methods: immersion of spice seeds in tryptic soy broth (TSB) plus Salmonella for 24 h (likely leading to inclusion of Salmonella in native microbiota biofilms formed around the seeds), application of cells grown in TSB, and/or application of cells scraped from tryptic soy agar (TSA). Postinoculation seeds were dried to a water activity of 0.3 within 24 h and held for 28 days. Seeds were sampled after drying (time 0) and periodically during the 28 days of storage. Salmonella cells were enumerated by serial dilution and plated onto xylose lysine Tergitol (XLT4) agar and TSA. Recovery of Salmonella was high after 28 days of storage but was dependent on inoculation method, with 4.05 to 6.22 and 3.75 to 8.38 log CFU/g recovered from peppercorns and cumin seeds, respectively, on XLT4 agar. The changes in surviving Salmonella (log CFU per gram) from initial inoculation levels after 28 days were significantly smaller for the biofilm inclusion method (+0.142pepper, +0.186cumin) than for the other inoculation methods (–0.425pepper, –2.029cumin for cells grown on TSA; –0.641pepper, –0.718cumin for dry transfer; –1.998pepper for cells grown in TSB). In most cases, trends for reductions of total aerobic bacteria were similar to those of Salmonella. The inoculation method influenced the recoverability of Salmonella from whole peppercorns and cumin seeds after drying. The most stable inoculum strategies were dry transfer, 24-h incubation of Salmonella and spices in TSB (i.e., potential inclusion of Salmonella within native microbiota biofilms), and inoculation of Salmonella cells grown on TSA subsequent to drying. However, with the dry transfer method it was difficult to obtain the large amount of inoculum needed for inactivation studies.
Article
Salmonella enterica is a leading human pathogen responsible for foodborne outbreaks worldwide. In the last decade, foods with low water activity (aw) and high-fat content have been involved in an increased occurrence of foodborne outbreaks. This research focuses on the foodstuff tahini, which is often linked to Salmonella infection outbreaks and recalls. Thermal treatments are suggested to reduce microbial populations in tahini, but little is known about its effectiveness against Salmonella. Our major objectives were to study the survival of Salmonella Typhimurium in tahini treated at temperatures ≥70°C, and to identify food related factors that could influence its survival. Based on our experimental results the thermal treatments at 70°C, 80°C and 90°C are suitable to inactivate only a partial population of Salmonella. The death of Salmonella in tahini matches a biphasic logarithmic inactivation model, with a maximal 3-log reduction after 1 hour at 90°C. Moreover, we observed that a second thermal treatment the day after the first treatment, is significantly less effective compared with the first thermal treatment. The inactivation rates of Salmonella in 100% tahini are almost 4-log lower than in water/tahini emulsions at 70°C, with negative linear correlation between D-value and aw, and the Salmonella susceptibility to heat in sesame oil/tahini emulsions is affected by the matrix of pre-acclimation. Bacteria that had been acclimated in tahini kept their heat resistance, while acclimation in sesame oil before mixing in the preheated oil/tahini emulsions resulted in a sharp decline within 2 minutes at 70°C. According to these findings, tahini producers’ current pasteurization processes are not sufficient to achieve the required 5-log reduction. Furthermore, we suggest that due to the tahini heterogenicity, the aw in the micro-environment of each bacterium, which is shaped by the tahini substances, plays an essential role in Salmonella’s survival in tahini at temperatures ≥70°C.
Article
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The objective of this study was to evaluate the effect of roasting on the nutritional and cosmetic potential of oil extracted from kernels of C. lanatus, which is one of the most widespread Cucurbitaceae species in Sub-Saharan Africa. The dried kernels (DKO) and roasted kernels (RKO) oils were extracted by cold press and hot using hexane. The physicochemical properties of these oils were evaluated. The results showed that C. lanatus roasted kernels were important sources of lipids (40.12 %) and protein (37.50 %). Oil extracted by press was of high quality, compared to that extracted by hexane. The study of the roasting effect revealed that the physicochemical characteristics of DKO and RKO oils were significantly different, with the exception of their specific gravity (≈ 0.9) and their refractive index (≈ 1.47). The absorbance of the two oils decreased in the range of UV-A and UV-B wavelengths. Both oils had low oxalates content (≈ 0.05 %) and were free of phytates and cyanogenic glycosides. All these features suggest that the roasted kernels oil of the C. lanatus could be used in food and cosmetic industries.
Article
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Bu çalışmada, gıdalarda Salmonella aranması amacıyla, önzenginleştirme aşamasında ISO tarafından önerilen tamponlanmış peptonlu su ile FDA tarafından kimi gıdaların analizi için önerilen laktoz broth, S. Enteritidis ATCC 13076 ve S. Typhimurium ATCC 13311 olmak üzere iki farklı Salmonella serotipi için denenmiştir. Çalışmada, refakatçi flora olarak Escherichia coli ATCC 10536 suşu kullanılmıştır. Işınlanarak sterilize edilmiş kıyma ve UHT süt, ayrı ayrı olmak üzere S. Enteritidis + E. coli ve S. Typhimurium + E. coli ile bulaştırılmış, 37 oC'ta 24 saat inkübasyona bırakılmıştır. İnkübasyonun 15, 18, 21 ve 24. saatlerinde Salmonella ile E. coli sayımları selektif besiyeri kullanılarak yapılmış ve aynı zamanda pH değerleri ölçülmüştür. Denemelerin 2. aşamasında, Salmonella serotipleri asetik asit ile zayıflatılmış ve yukarıda belirtilen şekilde devam edilmiştir. Araştırma sonuçlarına göre, tamponlanmış peptonlu suda pH stabil kalmış (P >0.05) ancak laktoz brothta pH düşmüştür (P <0.05). pH'nın düşmesi Salmonella serotiplerinin tümüyle yok olmasına yetecek kadar olmamıştır ve her koşulda Salmonella sayımı gerçekleştirilmiştir. S. Typhimurium serotipi özellikle laktoz brothta S. Enteritidis serotipine kıyasla daha düşük (P <0.05) sayım sonucu vermiştir. Tüm denemelerde ilerleyen inkübasyon süresine bağlı olarak laktoz brothta pH düşmesi olmakla beraber, bu düşüşün Salmonella sayısında önemli bir etkisi olmamıştır (P >0.05).
Article
Significance and impact of the study: Contamination of halva (tahini halva) with Salmonella from raw materials or during production was documented. Halva and tahini have been involved in salmonellosis outbreaks in different countries. The study demonstrated enhanced survivability of stressed and unstressed Salmonella spp. in halva over a 12-month storage period at 10 and 25°C with lower log reductions than expected. Exposing Salmonella spp. to desiccation or heat stress prior product contamination may play a role in microbial survival in halva during storage. These findings serve as a model to halva producers to implement control measures to prevent Salmonella spp. contamination in halva.
Research
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Unpasteurized ingredients, such as contaminated sesame seeds or flour, may introduce Salmonella into bakery products. Therefore, the use of a validated baking process is critical to eliminate this pathogen. This study compared the effect of oven relative humidity (RH) on the reduction of Salmonella and yeast during baking of inoculated bread dough topped with inoculated sesame seeds. Salmonella was injected into individual portions of bun dough to yield populations of 7.0-8.0 log CFU/g; dough was proofed and then topped with dry, inoculated sesame seeds (6.0-7.0 log CFU Salmonella/g seed). The seeded buns and seeds alone were baked in dry (average ~3% RH) or moist (average 20% RH after wet bulb spike) oven conditions for 7 and 9 min, respectively, to match a "bun-color standard," as suggested by a commercial bakery. After complete baking, Salmonella and yeast populations in the bun had decreased > 5-log for both methods. In contrast, differences in oven RH affected inactivation on the surface seeds, with reductions of 3.6 and > 6.0 log Salmonella at the end of dry and moist baking, respectively. This study demonstrates that maintaining an average 20% relative humidity during baking enhances the lethality on the product surface, compared to ≤ 3% RH, while also maintaining quality.
Article
Factors that control pathogen survival in low water activity foods are not well understood and vary greatly from food to food. A literature search was performed to locate data on the survival of foodborne pathogens in low-water activity (<0.70) foods held at temperatures <37 °C. Data were extracted from 67 publications and simple linear regression models were fit to each data set to estimate log linear rates of change. Multiple linear stepwise regression models for factors influencing survival rate were developed. Subset regression modeling gave relatively low adjusted R² values of 0.33, 0.37, and 0.48 for Salmonella, E. coli and L. monocytogenes respectively, but all subset models were highly significant (p < 1.0e-9). Subset regression models showed that Salmonella survival was significantly (p < 0.05) influenced by temperature, serovar and strain type, water activity, inoculum preparation method, and inoculation method. E. coli survival was significantly influenced by temperature, water activity, and inoculum preparation. L. monocytogenes survival was significantly influenced by temperature, serovar and strain type, and inoculum preparation method. While many factors were highly significant (p < 0.001), the high degrees of variability show that there is still much to learn about the factors which govern pathogen survival in low water activity foods.
Article
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Tahini (sesame paste) is a traditional food. Numerous foodborne outbreaks have been associated with it. This study aimed to (i) explore the efficiency of 2450 MHz microwave heating at 220, 330, 440, 550, and 660 W on the inactivation of Salmonella spp, Escherichia coli O157:H7, and Listeria monocytogenes in tahini; (ii) determine the impact of desiccation and starvation stresses on pathogen survival; (iii) assess the impact of microwave heating on the physicochemical characteristics of tahini. The inoculated microorganisms in tahini were reduced with higher microwave power levels (p < 0.05) and longer exposure times. The D-values of unstressed Salmonella spp., Escherichia coli O157:H7, and L. monocytogenes ranged from 6.18 to 0.50 min, 6.08 to 0.50 min, and 4.69 to 0.48 min, respectively, at power levels of 220 to 660 W, with z-values of 410, 440, and 460 W, respectively. Generally, desiccation and starvation stress levels prior to heating increased microbial resistance to heat treatment. Microwave heating did not affect acid, peroxide, p-anisidine, or color values of tahini up to 90 °C. These findings reveal microwave heating as a potential method for lowering the risk of Salmonella spp., E. coli O157:H7 and L. monocytogenes in tahini with no compromise on quality.
Chapter
Food safety has emerged as a significant global threat to public health, national income, international trade implications, and nutrition security in developing and developed countries. However, developing countries including the Middle East region are expected to be at higher risk of foodborne diseases due to the weakness and fragment of food systems and ineffective approaches adapted to protect the health of consumers. Nevertheless, efforts to enhance the safety of foods particularly traditional products have been developed by multiple research studies. This chapter reviewed the biological, chemical, and physical interventions as well as using active packaging tools to control foodborne pathogens in traditional food products usually consumed in the Middle East. Many of these methods including natural antimicrobials, nonthermal techniques, and biocontrol agents showed significant activities in reducing the risks of foodborne illness in traditional food products in the Middle Eastern countries. However, these strategies should be optimized to appropriate performances allowing demonstrating their impact on food safety systems, and then, they could be adapted in national food regulations of these countries.
Article
This study determined the desiccation resistance of 37 Salmonella strains belonging to 16 serotypes isolated from the soybean meal production chain. Besides, the survival of strains from three Salmonella enterica serovars (S. Typhimurium, S. Schwarzengrund, and S. Havana) on dry- and wet-inoculated soybean meal through storage at 25 °C and 37 °C was evaluated. Desiccation resistance varied within strains of the same serotype and amongst strains of different serotypes. On the other hand, the isolation source did not affect desiccation resistance. The inoculation method did not influence the survival of the three Salmonella enterica strains in soybean meal, but the effects of serovars and temperature were statistically significant (p < 0.05). The Weibull model was fitted to Salmonella survival in this matrix data, with the time for the first decimal reduction (δ) ranging from 21.1 to 50.8 days at 25 °C and from 2.7 to 7.9 days at 37 °C, respectively. The increase in storage temperature led to a decrease in survival regardless of the variability among the three isolates. The ability of Salmonella enterica to resist desiccation and to survive long-term on soybean meal reinforces the need for strategies to control this pathogen in the soybean production chain.
Article
Various outbreaks and recalls have been associated with Listeria monocytogenes contamination of ready-to-eat (RTE) food products, including dips. High pressure processing (HPP) is useful for reducing levels of bacteria in many RTE food products, but its efficacy for reduction of pathogens in RTE dips is not well understood. In this study, laboratory-prepared hummus, tahini, baba ghanoush, guacamole, and pesto were initially treated with HPP at 350 MPa for up to 240 s to assess L. monocytogenes inactivation and determine D-values. D350 MPa-values in hummus, guacamole, and baba ghanoush were 105.3, 71.3, and 34.0 s, respectively. No significant reduction in L. monocytogenes levels was observed in tahini or pesto at 350 MPa for 240 s or after additional treatment for up to 600 s at 600 MPa (P > 0.05). Overall, the results of this study highlight the efficacy of HPP for reducing L. monocytogenes levels in certain RTE dips and but not in others.
Article
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Dehulled sesame seeds were roasted using different heat treatments. The effects of roasting treatments on the nutritive value, physicochemical properties and sensory properties of produced tahina were studied. Resultant tahina contained 586–594 g kg−1 crude oil, 219–226 g kg−1 crude protein and <30 g kg−1 crude fibre and ash. Crude protein, crude fibre, ash and N-free extract in tahina samples were not affected by roasting treatments. However, crude oil was decreased by steam roasting and hot plate roasting. Hot plate roasting was more effective in reducing raffinose content than other roasting treatments, whereas vacuum roasting was less effective in reducing raffinose content than other roasting treatments. Tahinas were good sources of essential amino acids, especially sulphur-containing amino acids, aromatic amino acids and tryptophan. Hot air roasted tahina followed by vacuum roasted tahina had higher total essential amino acid contents than steam roasted and hot plate roasted tahinas. Lysine was the first limiting amino acid in tahinas. Tahinas had a relatively high in vitro protein digestibility (over 83%). Tahina is a good source of niacin. Hot air roasted tahina had the highest content of B group vitamins compared with other tahina samples. Resultant tahinas had relatively high amounts of Na, Mg, K, Cu, Zn and Fe and a low amount of Ca. Roasting treatments did not affect the mineral contents. All roasted samples had a typical protein spectrum with a maximum absorption at 280 nm and minimum at 260 nm. However, the spectrum of hot air roasted tahina proteins was sharper than the spectra of other tahina proteins. Size exclusion HPLC fractionated tahina proteins into two fractions for hot roasted and vacuum roasted tahinas and three fractions for steam roasted and hot plate roasted tahinas. The gel filtration pattern of tahina proteins contained four peaks with identical elution volumes but different proportions. Hot air roasted and vacuum roasted tahinas had higher panel scores than steam roasted and hot plate roasted tahinas for all tested sensory properties.© 2000 Society of Chemical Industry
Article
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Sources and risk factors for contamination, survival, persistence, and heat resistance of Salmonella in low-moisture foods are reviewed. Processed products such as peanut butter, infant formula, chocolate, cereal products, and dried milk are characteristically low-water-activity foods and do not support growth of vegetative pathogens such as Salmonella. Significant food safety risk might occur when contamination takes place after a lethal processing step. Salmonella cross-contamination in low-moisture foods has been traced to factors such as poor sanitation practices, poor equipment design, and poor ingredient control. It is well recognized that Salmonella can survive for long periods in low-moisture food products. Although some die-off occurs in low-moisture foods during storage, the degree of reduction depends on factors such as storage temperature and product formulation. The heat resistance of Salmonella is affected by many factors, mostly by strain and serotypes tested, previous growth and storage conditions, the physical and chemical food composition, test media, and the media used to recover heat-damaged cells. Salmonella heat resistance generally increases with reducing moisture. Care must be taken when applying published D- and z-values to a specific food process. The product composition and heating medium and conditions should not be significantly different from the product and process parameters used by the processors.
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In November 2002, the first of three outbreaks of Salmonella Montevideo infection in Australia and New Zealand was identified in New South Wales, Australia. Affected persons were interviewed, and epidemiologically linked retail outlets inspected. Imported tahini was rapidly identified as the source of infection. The contaminated tahini was recalled and international alerts posted. A second outbreak was identified in Australia in June-July 2003 and another in New Zealand in August 2003. In a total of 68 S. Montevideo infections, 66 cases were contacted. Fifty-four (82%) reported consumption of sesame seed-based foods. Laboratory analyses demonstrated closely related PFGE patterns in the S. Montevideo isolates from human cases and sesame-based foods imported from two countries. On the basis of our investigations sesame-based products were sampled in other jurisdictions and three products in Canada and one in the United Kingdom were positive for Salmonella spp., demonstrating the value of international alerts when food products have a wide distribution and a long shelf life. A review of the controls for Salmonella spp. during the production of sesame-based products is recommended.
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The ability of Salmonella enterica serovar Typhimurium to survive environmental stress requires specific, coordinated, responses, which induce resistance to the stress condition. This study investigated the relative contribution of sigmaE and sigmaS, the sigma factors regulating extracytoplasmic and general stress response functions, respectively, to survival at low temperature and also in media of differing osmotic strength, conditions relevant to food preservation. To determine if low-temperature storage is a signal for sigmaE- and sigmaS-mediated survival, the ability of S. Typhimurium rpoE, rpoS and rpoE/rpoS mutants to survive in a saline starvation-survival model at a refrigeration temperature (4.5 degrees C) was examined. Under these conditions, the rpoE mutant was significantly (P<0.05) compromised compared to the parent and to an rpoS mutant. The double mutant in rpoE and rpoS displayed a cumulative defect in survival. In hyperosmotic environments (low aw) containing 6 % NaCl and at refrigeration temperature, both sigma factors were important for maximum survival but sigmaS played the dominant role. Analysis of the metabolic activity of starved populations at 4.5 and 37 degrees C revealed significantly (P<0.001) elevated electron-transport system activity in mutants in rpoE and rpoS, indicating a role for sigmaE- and sigmaS-regulated genes in maintaining energy homeostasis. Together these data demonstrate that sigmaE and sigmaS are important for survival of S. Typhimurium in conditions encountered during food processing and that the relative contribution of sigmaE and sigmaS is critically dependent on the precise nature of the stress.
Article
On September 27, 2011, three clinical isolates of Salmonella enterica serotype Bovismorbificans with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns were identified by the District of Columbia Public Health Laboratory (PHL). Human infection with S. Bovismorbificans is rare in the United States. Through query of PulseNet, the national molecular subtyping network for foodborne disease surveillance, six additional cases with indistinguishable PFGE patterns were identified in three states (Maryland, Michigan, and Virginia) during the prior 60 days. All nine patients had eaten at restaurants in the District of Columbia (DC) or northern Virginia <2 weeks before illness onset. This report summarizes the investigation led by the DC Department of Health (DOH), in which 23 cases of S. Bovismorbificans infections were identified among persons from seven states and DC, with illness onset during August 19-November 21, 2011. On May 30, 2012, traceback indicated that contaminated tahini (sesame seed paste) used in hummus prepared at a Mediterranean-style restaurant in DC was a plausible source of Salmonella infections. DOH restricted the sale of hummus and prohibited the use of hummus ingredients in other food items at implicated restaurants to prevent further illness. This investigation also illustrates challenges associated with ingredient-driven outbreaks and the value of PulseNet for identifying clusters of cases that are geographically dispersed.
Article
The heat resistance of food-poisoning outbreak and non-outbreak associated strains of Salmonella (S. Enteritidis, S. Montevideo, S. Napoli, S. Oranienburg, S. Poona, S. Senftenberg and S. Typhimurium) was established in confectionery-related materials such as crushed cocoa bean and hazelnut shells at low moisture contents (≤4% w/w). The two most heat resistant strains in cocoa and hazelnut shells at ca. 4% w/w moisture were S. Oranienburg and S. Enteritidis PT30. Both strains were associated with outbreaks from dried materials. Their D100°C values were ca. 2.5min in crushed cocoa bean shells and 7–11min in crushed hazelnut shells. Addition of moisture to ca. 7% w/w markedly reduced D-values (D80°C of 2–4.5min) for both strains in the two matrices.
Article
Survival and growth characteristics of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in six commercial butter, yellow fat spread, and margarine products that had been subjected to temperature and physical abuse were determined. Sweet cream whipped salted butter, sweet cream whipped unsalted butter, salted light butter, two yellow fat spreads, and light margarine were surface inoculated with pathogens to simulate incidental post-processing contamination. Products (31–78% fat, pH 4.05–6.40) at 4.4°C were then held at 37°C under high relative humidity (85%) for 1h to induce condensation of water on the surface before storing at 4.4°C or 21°C for up to 21 days. All three pathogens grew between 1 and 2 days in sweet cream whipped salted butter (pH 6.40) stored at 21°C. L. monocytogenes began to grow between 7 and 14 days on the same product stored at 4.4°C. None of the pathogens grew on sweet cream whipped unsalted butter (pH 4.51), salted light butter (pH 4.58), yellow fat spreads (pH 4.05 and 5.37), or light margarine (pH 5.34) stored at 4.4 or 21°C for 21 days. Rates of inactivation of the three pathogens were more rapid in products stored at 21°C, compared to 4.4°C, and in products containing preservatives and acidulants. The adverse affects of acidic pH and preservatives presumably were amplified at 21°C compared to 4.4°C. In a second study, products at 37°C were physically abused by pummeling for 3min in a stomacher before inoculating with pathogens and storing at 4.4°C or 21°C for up to 21 days. Salmonella, but not E. coli O157:H7 or L. monocytogenes, grew in sweet cream whipped salted butter at 21°C. None of the pathogens grew in the other five products stored at 21°C or in any of the six products stored at 4.4°C.
Article
In response to increased concerns about spice safety, the U.S. FDA initiated research to characterize the prevalence of Salmonella in imported spices. Shipments of imported spices offered for entry to the United Sates were sampled during the fiscal years 2007-2009. The mean shipment prevalence for Salmonella was 0.066 (95% CI 0.057-0.076). A wide diversity of Salmonella serotypes was isolated from spices; no single serotype constituted more than 7% of the isolates. A small percentage of spice shipments were contaminated with antimicrobial-resistant Salmonella strains (8.3%). Trends in shipment prevalence for Salmonella associated with spice properties, extent of processing, and export country, were examined. A larger proportion of shipments of spices derived from fruit/seeds or leaves of plants were contaminated than those derived from the bark/flower of spice plants. Salmonella prevalence was larger for shipments of ground/cracked capsicum and coriander than for shipments of their whole spice counterparts. No difference in prevalence was observed between shipments of spice blends and non-blended spices. Some shipments reported to have been subjected to a pathogen reduction treatment prior to being offered for U.S. entry were found contaminated. Statistical differences in Salmonella shipment prevalence were also identified on the basis of export country.
Article
The high heat resistance of Salmonella in foods with low water activity raises particular issues for food safety, especially chocolate, where outbreak investigations indicate that few colony-forming units are necessary to cause salmonellosis. This study evaluated the efficiency of cocoa roasting and milk chocolate conching in the inactivation of Salmonella 5-strain suspension. Thermal resistance of Salmonella was greater in nibs compared to cocoa beans upon exposure at 110 to 130°C. The D-values in nibs were 1.8, 2.2 and 1.5-fold higher than those calculated for cocoa beans at 110, 120 and 130°C. There was no significant difference (p>0.05) between the matrices only at 140°C. Since in the conching of milk chocolate the inactivation curves showed rapid death in the first 180min followed by a lower inactivation rate, and two D-values were calculated. For the first time interval (0-180min) the D-values were 216.87, 102.27 and 50.99min at 50, 60 and 70°C, respectively. The other D-values were determined from the second time interval (180-1440min), 1076.76min at 50°C, 481.94min at 60°C and 702.23min at 70°C. The results demonstrated that the type of matrix, the process temperature and the initial count influenced the Salmonella resistance.
Article
Sesame paste (tahin) is produced by milling hulled, roasted, sesame seeds. In this study, a hot-air roasting process for the production of sesame paste was optimised by response surface methodology (RSM) over a range of air temperatures (120–180 °C) for various times (30–60 min). The colour parameters (L, a and b values), browning index (BI), hardness, fracturability and moisture content of the seeds were used as response parameters to develop predictive models and optimise the roasting process. Increases in roasting temperature and time caused increases in the a and b values and in the BI. The hardness and fracturability of seeds also decreased with increasing roasting temperature and time. The quadratic and linear models developed by RSM adequately described the changes in the colour values and textural parameters, respectively. The result of RSM analysis showed that all colour parameters and textural parameters should be used to monitor the roasting of sesame seeds in a hot-air roaster. To obtain the desired colour and texture, the optimum roasting range for production of sesame paste was determined as 155–170 °C for 40–60 min. Copyright © 2006 Society of Chemical Industry
Article
In this paper, rheological properties of tahin are reported at temperatures from 20 to 70 °C and shear rates in the range 0.13–500 s−1. Temporary hysteresis loops were observed in the first cycle of the flow curves. The steady shear behaviour of tahin was pseudoplastic and described by a power law model. The consistency coefficient exhibited strong temperature dependence for which the activation energy of flow was 21.6 kJ mol−1. The flow behaviour index of tahin tended to increase whereas the consistency coefficient tended to decrease during storage at room temperature. Tahin oil exhibited Newtonian behaviour with a strong dependence of viscosity on temperature. The activation energy of flow for tahin oil was 35.7 kJ mol−1. While reconstituted suspensions containing up to 20% solids exhibited Newtonian behaviour, those with more solids and the original tahin showed pseudoplastic behaviour. The Krieger–Dougherty model fitted the suspension viscosity data well. Below 20% solids level there was no effect of particle size on the viscosity of the reconstituted suspensions. It was shown that for the same amount of solids the viscosity of a ‘polydisperse’ suspension was lower than that of a ‘monodisperse’ suspension. Copyright © 2004 Society of Chemical Industry
Article
Studies were done to determine the effectiveness of hot air drying, dry roasting, and oil roasting in killing Salmonella on pecan nutmeats. Pecan halves and pieces were inoculated by immersion in a five-serotype suspension of Salmonella or by surface application of powdered chalk containing the pathogen. Hot air treatment of low-moisture (2.8 to 4.1%) and high-moisture (10.5 to 11.2%) immersion-inoculated nutmeats (initial population, 6.18 to 7.16 log CFU/g) at 120°C for 20 min reduced the number of Salmonella by 1.18 to 1.26 and 1.89 to 2.04 log CFU/g, respectively. However, regardless of the moisture content, hot air treatment of pecan halves containing 0.77 log CFU/g at 120°C for 20 min failed to eliminate Salmonella. Reductions were >7 log CFU/g when dry pieces were dry roasted at 160°C for 15 min. Treatment of halves at 140°C for 20 min, 150°C for 15 min, or 170°C for 10 min reduced Salmonella by 5 log CFU/g. The pathogen was slightly more heat resistant in immersion-inoculated nutmeats than on surface-inoculated nutmeats. Exposure of immersion-inoculated pieces to peanut oil at 127°C for 1.5 min or 132°C for 1.0 min reduced the number of Salmonella by 5 log CFU/g. Treatment of halves at 138°C for 2.0 min reduced Salmonella by 5 log CFU/g; treatment at 132°C for 2.5 to 4.0 min did not always achieve this reduction. Hot air treatment cannot be relied upon to reduce Salmonella by 5 log CFU/g of raw pecan nutmeats without changing sensory qualities. Treatment temperatures and times typically used to oil roast nutmeats appear to be sufficient to reduce Salmonella by 5 log CFU/g.
Article
The efficacy of a commercial seed washer and 1 and 3% peroxyacetic acid or 20 000 ppm calcium hypochlorite for reducing Salmonella on alfalfa seeds was investigated. Alfalfa seeds were inoculated with Salmonella Stanley to achieve c. 5 log CFU g(-1). Seeds were then treated with 1 or 3% peroxyacetic acid or 20 000 ppm calcium hypochlorite for 15 min in a commercial seed washer that uses air to enhance contact of the sanitizer with the seed. Experiments were also conducted using industry and laboratory methods. An c. 1-log reduction in number of Salm. Stanley was demonstrated regardless of the chemical treatment or method of treatment. Although this 1-log reduction was significant (P < 0.05), differences among the treatments were not significant. Treating the seed with 1 and 3% peroxyacetic acid resulted in similar Salm. Stanley reductions of 1.77 and 1.34 log, respectively, not being statistically significant (P > 0.05). These results suggest that under conditions tested, 1 or 3% peroxyacetic acid solutions are equally effective as 20 000 ppm of Ca(OCl)2 in the reduction of Salm. Stanley on alfalfa seed when used in conjunction with a commercial seed washer. A 1% peroxyacetic acid solution could potentially be used in place of 20 000 ppm of Ca(OCl)2 for treatment of seeds used for sprouting. The commercial seed washer did not enhance removal of Salm. Stanley from alfalfa seeds, but did facilitate removal of excess soil from seeds.
Article
Sesame seed products have recently been associated with a number of Salmonella outbreaks in the UK and elsewhere. Aside from sesame seeds, there is little published information on the prevalence of Salmonella spp. in edible seeds. A study of 3735 samples of retail edible dried seeds in the UK was therefore carried out between October 2007 and March 2008 to assess their microbiological safety in relation to Salmonella contamination and levels of Escherichia coli, an indicator of faecal contamination. Overall, Salmonella was detected in 23 samples (0.6%), of which over half (57%) were sesame seeds. Other seeds contaminated with Salmonella were linseed (1 sample), sunflower (1 sample), alfalfa (1 sample), melon (4 samples) and mixed seeds (3 samples). E. coli was detected in 9% of samples, with 1.5% containing unsatisfactory levels (> or = 10(2)/g). These included melon, pumpkin, sesame, hemp, poppy, linseed, sunflower and mixed seeds. The UK retailers affected by the detection of Salmonella in their products recalled the contaminated batches, and Food Standards Agency food alerts were issued to advise against the consumption of affected seed products. This study highlights the importance of good hygiene practices and effective decontamination procedures during the production of these products.
Article
The thermal resistance of Salmonella senftenberg 775W was determined in meat and bone meal and chick starter contaminated by broth culture and by a simulated-natural method employing cells grown and dried in wet meat and bone meal base. Data obtained from modified thermal-death-time (TDT) tubes indicated that, except for initial fast killing rates, the heat resistance of S. senftenberg 775W in dry feeds is an exponential function of heating time, as in liquid media. The z values obtained (18 to 20 F) were higher than for vegetative cells heated in liquid media and similar to those of the more heat-resistant spores. Heat resistance in feeds was markedly higher with contamination by the simulated-natural method than by broth cultures. Increasing feed moisture levels decreased heat resistance, with a declining effect starting between 15 and 20% moisture. Results obtained with a laboratory-model steam feed conditioner indicated that the data obtained from TDT tubes are generally applicable to requirements for industrial-feed pasteurization. It is suggested that feed pasteurization can be accomplished by processing conditions which reduce the salmonella population by five log cycles. Processing feed at a moisture level of 15% or greater and a temperature of 190 F is indicated. Data are provided to allow prediction of thermal destruction under varying moisture and temperature conditions by use of the formula log D2= log D1+(1/z)( T1- T2).
Article
A traditional low-moisture confectionery, halva, was studied with respect to microbial stability over prolonged storage. It was kept under refrigeration or at room temperature in air-sealed or vacuum packaging in moisture-proof material. Microbial stability of commercial samples was evaluated with regard to the following groups of microorganisms: aerobic plate count, Enterobacteriaceae, enterococci, sulfite-reducing clostridia, aerobic mesophilic and thermophilic sporeformers, staphylococci, Staphylococcus aureus, Salmonella spp., lipolytic microorganisms, yeasts and molds. In all samples tested the above microorganisms were in acceptable levels, while sulfite-reducing clostridia, Salmonella spp., and molds were not detected. The potential for survival of Salmonella Enteritidis in the product was evaluated by artificial contamination. Inoculum surviving after the immediate significant decrease was still recovered after 8 months of storage. The reduction of salmonellae during storage cannot be predicted on the basis of the aw alone.
Article
The heat resistance of Salmonella weltevreden inoculated into flour and heated in hot air was determined for (a) an initial water activity (aw) range of 0.20 to 0.60 prior to heating, (b) a range of storage relative humidities of 6.0 to 35.5% prior to heating, and (c) temperatures of 57 to 77 degrees C. The death curves obtained were biphasic, demonstrating an initial rapid decline in the numbers of survivors (1.0- to 1.5-log reductions) during the first 5 to 10 min of heating for all the temperature-water activity combinations tested. Following this initial rapid decline in the number of cells, a linear survivor curve was obtained where inactivation occurred at a slower rate. The initial decline in survivors coincided with a rapid decrease in the water activity of all the samples tested. Irrespective of the initial water activity level in the samples prior to heating, the aw decreased to < 0.2 during the first 5 to 10 min of heating. The D values obtained for these experimental parameters ranged from a D60-62 of 875 min at an initial aw of 0.4 to a D63-65 of 29 min at an initial aw of 0.5. The results demonstrated that, for any temperature, as the initial water activity of the sample prior to heating decreased, the heat resistance of the cells increased. The z values obtained from these data ranged from 15.2 to 53.9 degrees C. The relative humidity during storage prior to heating did not appear to have a significant effect on the heat resistance of S. weltevreden in flour. These results demonstrate that the amount of available water in foods that are considered to be "dry" (i.e., with a water activity less than 0.60) will significantly influence the effectiveness of the heat processing of foods and, in addition to the temperature, the aw prior to heating is a critical controlling factor during these processes.
Article
"Bacteria have evolved adaptive networks to face the challenges of changing environments and to survive under conditions of stress. Therefore, the efficiencies of inactivation and preservation methods need to be assessed, especially with regard to the enormous potential of food pathogens to adapt to a wide variety of stress conditions. All adaptive responses, whether to changing nutrients or to various stresses encountered in minimal processing, involve a series of genetic switches that control the metabolic changes taking place. A common regulatory mechanism involves the modification of sigma (sigma) factors whose primary role is to bind to core RNA polymerase conferring promoter specificity directing expression of specialty regulons involved in heat-shock response, the chemotactic response, sporulation, and general stress response. Examples of the latter regulon in Gram-positive bacteria (the sigmaB regulon) and in Gram-negative bacteria (the RpoS regulon) will be discussed in more detail. Cellular adaptive mechanisms to starvation, cold shock, heat shock, (weak) acids, high osmolarity and high hydrostatic pressure will be described and their significance in food preservation and safety will be discussed."
Article
In 1996, the first documented outbreak of salmonellosis associated with the consumption of peanut butter was reported. This study was undertaken to determine survival characteristics of high (5.68 log10 cfu g(-1)) and low (1.51 log10 cfu g(-1)) inocula of a five-serotype mixture of Salmonella in five commercial peanut butters and two commercial peanut butter spreads. Populations in samples inoculated with 5.68 log10 cfu g(-1) and stored for 24 weeks at 21 or 5 degrees C decreased 4.14-4.50 log10 cfu g(-1) and 2.86-4.28 log10 cfu g(-1), respectively, depending on the formulation. The order of retention of viability was: peanut butter spreads > traditional (regular) and reduced sugar, low-sodium peanut butters > natural peanut butter. Differences in rates of inactivation are attributed to variation in product composition as well as size and stability of water droplets in the colloidal matrix, which may influence nutrient availability. With the exception of natural peanut butter, products initially inoculated with 1.51 log10 cfu of Salmonella g(-1) (32 cfu g(-1)) were positive for the pathogen after storage for 24 weeks at 5 degrees C. At 21 degrees C, however, with the exception of one peanut butter spread, all products were negative for Salmonella after storage for 24 weeks. Post-process contamination of peanut butter and spreads with Salmonella may to result in survival in these products for the duration of their shelf life at 5 degrees C and possibly 21 degrees C, depending on the formulation.
Article
In the context of an international outbreak of multiresistant Salmonella Typhimurium DT 104 that was correlated to the consumption of halvah ("helva," an Asian candy made from sesame seed), we examined several sesame seed products for the occurrence of Salmonella. Of 117 ready-to-eat food items containing sesame, we isolated salmonellae from 11 (9.4%) samples. In addition to finding Salmonella Typhimurium DT 104 in the halvah involved in the outbreak, we also isolated different Salmonella Typhimurium strains out of halvah from other manufacturers and countries of origin, as well as Salmonella Offa, Salmonella Tennessee, and Salmonella Poona from sesame paste (tahini) and sesame seed, which is sold for raw consumption in cereals.
Article
To study the factors and mechanisms involved in microorganisms' death or resistance to temperature in low-water-activity environments, a previous work dealt with the viability of dried microorganisms immobilized in thin-layer on glass beads. This work is intended to check the efficiency of a rapid heating-cooling treatment to destroy microorganisms that were dried after mixing with wheat flour or skim milk. The thermoresistance of the yeast Saccharomyces cerevisiae and the bacterium Lactobacillus plantarum were studied. Heat stress was applied at two temperatures (150 or 200 degrees C) for treatments of one of four durations (5, 10, 20, or 30 s) and at seven levels of initial water activity (a(w)) in the range 0.10 to 0.70. This new treatment achieved a microbial destruction of eight log reductions. A specific initial water activity was defined for each strain at which it was most resistant to heat treatments. On wheat flour, this initial a(w) value was in the range 0.30-0.50, with maximal viability value at a(w)=0.35 for L. plantarum, whatever the temperature studied, and 0.40 for S. cerevisiae. For skim milk, a variation in microbial viability was observed, with optimal resistance in the range 0.30-0.50 for S. cerevisiae and 0.20-0.50 for L. plantarum, with minimal destruction at a(w)=0.30 whatever the heating temperature is.
Article
The enteric pathogen Salmonella enterica is exposed to a number of stressful environments during its life cycle within and outside its various hosts. During intestinal colonisation Salmonella is successively exposed to acid pH in the stomach, to the detergent-like activity of bile, to decreasing oxygen supply, to the presence of multiple metabolites produced by the normal gut microflora and finally it is exposed to cationic antimicrobial peptides present on the surface of epithelial cells. There are four major regulators controlling relevant stress responses in Salmonella, namely RpoS, PhoPQ, Fur and OmpR/EnvZ. Except for Fur, inactivation of genes encoding the other stress regulators results in attenuated virulence and such mutants can therefore be considered as vaccine candidates. In contrast, a decrease in oxygen supply monitored by Fnr and ArcAB, or oxidative stress controlled by OxyR and SoxRS is not regarded as a stress associated with host colonisation since inactivation of either of these systems does not result in reductions in colonisation. The role of quorum-sensing through luxS and sdiA is also considered as a regulator of virulence and colonisation.
Article
Recent large foodborne outbreaks caused by Salmonella enterica serovars have been associated with consumption of foods with high fat content and reduced water activity, even though their ingredients usually undergo pasteurization. The present study was focused on the heat tolerance of Salmonella enterica serovars Agona, Enteritidis, and Typhimurium in peanut butter. The Salmonella serovars in the peanut butter were resistant to heat, and even at a temperature as high as 90 degrees C only 3.2-log reduction in CFU was observed. The obtained thermal inactivation curves were upwardly concave, indicating rapid death at the beginning (10 min) followed by lower death rates and an asymptotic tail. The curves fitted the nonlinear Weibull model with beta parameters < 1, indicating that the remaining cells have a lower probability of dying. beta at 70 degrees C (0.40 +/- 0.04) was significantly lower than beta at 80 degrees C (0.73 +/- 0.19) and 90 degrees C (0.69 +/- 0.17). Very little decrease in the viable population (less than 2-log decrease) was noted in cultures that were exposed to a second thermal treatment. Peanut butter is a highly concentrated colloidal suspension of lipid and water in a peanut meal phase. We hypothesized that differences in the local environments of the bacteria, with respect to fat content or water activity, explained the observed distribution and high portion of surviving cells (0.1%, independent of the initial cell number). These results demonstrate that thermal treatments are inadequate to consistently destroy Salmonella in highly contaminated peanut butter and that the pasteurization process cannot be improved significantly by longer treatment or higher temperatures.
Article
In Fall 2006, four separate outbreaks of foodborne illness associated with the consumption of fresh produce occurred in the United States. In follow-up investigations, spinach, lettuce, and tomatoes were identified as the vehicles of illness. Epidemiologic investigations subsequently focused on finding the specific growing regions using traceback records. While the areas most likely involved in the outbreaks have been identified, the specific mode of contamination remains unconfirmed. Suspected risk factors in these cases include: proximity of irrigation wells and surface waterways exposed to faeces from cattle and wildlife; exposure in fields to wild animals and their waste materials; and improperly composted animal manure used as fertilizer. Difficulty in deciphering these and other on-farm routes of contamination is due to the sporadic nature of these events. Hence, evidence to support these contamination modes is based largely on experimental studies in the laboratory and field. Still at issue is the relevance of internalization of pathogens, whether this occurs through the roots and plant vascular tissues of vegetables and fruits or through plant surfaces into cracks and crevices. Potential for these events, conditions under which the events occur, and pathogen survival following these events, are questions that still need to be answered. Answers to these questions will ultimately affect the type of interventions needed for application postharvest. Currently, many chemical and biological interventions can reduce surface pathogens and minimize cross-contamination, however, they are largely ineffective on internalized pathogens. In the event internalization is a significant route of contamination in the field, physical interventions (irradiation and high pressure) may be needed to minimize risk. Ultimately, risk assessment studies will be useful tools in developing risk management strategies for the produce industry.
Article
This study was undertaken to determine survival characteristics of inocula of a 3-strain mixture of Salmonella Tennessee in 5 commercial brands of peanut butter (A, B, C, D, and E). Inoculated peanut butter was stored at 4 (refrigerator temperature) and 22 degrees C (room temperature) for up to 14 d. After 1, 3, 5, 7, and 14 d, surviving cells, including injured cells, were enumerated on appropriate selective agar, including use of the agar overlay method. Populations in samples inoculated with 10(6-7) CFU/g and stored for 14 d at 4 and 22 degrees C decreased by 0.15 to 0.65 and 0.34 to 1.29 log CFU/g, respectively, depending on the formulation. Peanut butter A showed a significantly lower number of S. Tennessee cells when stored at 22 degrees C for 14 d, compared to 4 degrees C (P < 0.05). However, there was no significant difference between the levels of S. Tennessee at 4 and 22 degrees C in products B, C, D, and E (P > 0.05).
Les corps gras alimentaires: aspects microbiologiques. Revue Francaise des Corps Gras 32
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Physical and chemical properties and fatty acid composition of tahin (sesame paste)
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Preventing Salmonella contamination of peanut products. 13th Annual USA Peanut Congress
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Doyle, M., 2009. Preventing Salmonella contamination of peanut products. 13th Annual USA Peanut Congress, Amelia Island, Florida.
Effect of temperature, pH, water activity and pressure on growth. Escherichia coli and Salmonella Typhimurium: cellular and molecular biology
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Salmonella (non-typhoidal) in high lipid foods made from sesame seeds, peanuts or cocoa beans
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Lake, R., King, N., Cressey, P., Gilbert, S., 2010. Salmonella (non-typhoidal) in high lipid foods made from sesame seeds, peanuts or cocoa beans. Prepared for New Zealand Food Safety Authority under project MRP/08/01.