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Determination of ready-to-eat vegetable salad shelf-life
Abstract
The shelf-life of ready-to-eat vegetable salads established by manufacturers is usually 7-14 days depending on the type of vegetable, and is determined by loss in organoleptic qualities. A more objective method to predict shelf-life and spoilage would be desirable. The present study monitored the evolution of spoilage organisms in a mixed salad of red cabbage, lettuce and carrot stored at 4 degrees C, 10 degrees C and 15 degrees C. Changes in carbon dioxide and oxygen concentrations and pH were also monitored. Predictive modelling was used to established a theoretical shelf-life time as a function of temperature. Lactic acid bacteria at levels of 10(6) cfu/g appeared to be related to both spoilage and theoretically-predicted shelf-life values.
... However, LAB counts on the FPPE-coated fresh-cut cantaloupe products significantly increased by approximately 1.4 log within 1 day when the products were stored at room temperature (23 ± 2 • C) (p < 0.05; Figure 1c). While LAB can serve as beneficial bacteria, they are also known to cause spoilage in many ready-to-eat foods (García-Gimeno & Zurera-Cosano, 1997). An ecological study by Salama et al. (1995) indicated that cantaloupe may be contaminated by Lactococcuslactis ssp. ...
Fresh‐cut cantaloupes are highly susceptible to contamination by foodborne pathogens and spoilage‐causing microorganisms. This study evaluated the efficacy of a probiotic coating produced by fermenting Lactiplantibacillus plantarum 299 V in pomelo peel extract in combination with vacuum packaging in controlling the microbial loads of fresh‐cut cantaloupe during storage. As temperature abuse is common in transportation and at retail sale of such products in many countries, we evaluated their efficacy at different temperatures. Both the probiotic edible coating and vacuum packaging, when used alone, effectively inhibited microbial growth in fresh‐cut cantaloupe at all the tested temperatures. The combination had a statistically significant synergistic effect (p < 0.05) on reducing psychrotrophic total counts (4.5 ± 0.3 log lower than control on day 9) and yeast and mold (>3.1 log lower than control on day 9) at 4°C, Listeria monocytogenes (2.9 ± 0.2 log lower than control on day 6) at 12°C, and yeast and mold (3.1 ± 0.7 log lower than control on day 2) and L. monocytogenes (4.6 ± 0.4 log lower than control on day 2) at room temperature (23 ± 2°C). The solution proposed in this study has the potential to increase the resilience of products to temperature abuse, which can impact the safety of the food supply.
... LAB are psychrotrophic bacteria that have adapted to industrial environments, and can thus contaminate foods easily [78]. Spoilage related to lactic acid production can start when LAB levels reach 6 log, and will eventually be clearly detected at high levels of 9 log [42,79]. The initial LAB counts were 4.6 log (CFU/g) at day 0 and the high levels of 9 logs were not reached in any of the 10 treatments at day 21, but were exceeded in all the remaining 5 treatments at day 45. ...
Hummus is a traditional and very popular Mediterranean ready-to-eat (RTE) food, with growing popularity worldwide. However, it has a high water activity and is susceptible to microbial growth and post-process contamination that limit its quality and shelf-life. For this purpose, the present study compared the use of several antimicrobials, alone or in combination, for hummus preservation during storage (4 • C), for up to 45 days. The chemical preservative potassium sorbate 0.09% (S) was evaluated, along with three natural antimicrobials: garlic 1.25% (G); vinegar 5% (V); natamycin 0.002% (N); or their combination: garlic 1.25%-vinegar 5% (GV); vinegar 5%-natamycin 0.002% (VN); garlic 1.25%-natamycin 0.002% (GN); and garlic 1.25%-vinegar 5%-natamycin 0.002% (GVN) to increase the shelf-life of hummus. A thymol and carvacrol mixture 0.2% (O) was also assessed to preserve and develop a new oregano-flavored hummus. All treatments that included vinegar used alone or in combination had significantly higher antimicrobial effectiveness than the other treatments. They achieved 2.2-3.2, 1.8-3.1, and 1.4-2.1 log reductions in total aerobic counts (TAC), Pseudomonas spp., and lactic acid bacteria (LAB), respectively, as compared to the control samples © at day 21. Therefore, the shelf-life of C, S, N, G, GN, and O was around (ca.) 19 days, compared to an extended one of ca. 25 days for V and VN, and ca. 30 days for GV and GVN. Sensory analysis showed the highest acceptability for C, N, S, V, and VN, followed by GV and GVN, and the lowest was for G, GN, and finally O. The findings provide potential alternatives to chemical preservatives, which could be used for natural hummus preservation and shelf-life extension.
Ozone, a potent oxidant, works well against various bacteria in fruits and vegetables. Applying Ozone has shown promising results in addressing issues faced by the food industry, such as mycotoxin and pesticide residues. Ozonation is safe for food applications since it breaks down naturally without leaving dangerous residues in the treatment media. Ozone can negatively affect items when employed incorrectly, including reductions in sensory quality. For Ozone's safe and efficient application, treatment parameters for each product type should be precisely specified.
The aim of this study was to investigate the antibacterial, antibiofilm, antioxidant and shelf life protective potentials of infusion, decoction, and room temperature samples of sumac fruits prepared as used by the local people against three foodborne pathogens including Bacillus cereus, Escherichia coli O157:H7, and Staphylococcus aureus isolated from food samples. The room temperature samples of sumac showed a remarkable antibacterial activity (81.25%) against S. aureus. Infusion and decoction samples of sumac fruit showed an effective antibacterial activity (∼70%) against E. coli O157:H7. Moderate efficacy against B. cereus was observed in all treatment groups. Antibiofilm effects of sumac were observed against B. cereus and S. aureus, but not against E. coli O157:H7. The total antioxidant activity was found to be close to the reference compounds. The twenty-two phenolic and flavonoid chemical compounds (gallic acid, gentisic acid, protocatechuic acid, protocatechualdehyde, 4-OH-benzoic acid, salicylic acid, chlorogenic acid, cafeic acid, p-coumaric acid, ferulic acid, rosmarinic acid, sinapic acid, trans-cinnamic acid, rutin, resveratrol, myricetin, naringenin, quercetin, luteolin, kaempferol, apigenin, and chrysin) were identified by Liquid Chromatography Mass Spectrometer (LC-MS/MS) and these molecules were analyzed by computational analyses using SwissADME, admetSAR 3.0 and the AntiBac-Pred web tool. In addition, the antibacterial efficacy of sumac fruit extracts was tested on mixed Mediterranean salad samples to evaluate the shelf-life enhancing effect. The efficacy of sumac fruit against common foodborne pathogens suggests that the ethnobotanical use of sumac may provide protection against bacterial diseases and can be utilized as an additive and/or ingredient in the food industry.
After harvesting, pathogens can infect fresh vegetables in different ways. Pathogenic bacteria
associated with fresh vegetables can cause widespread epidemics associated with foodborne
illness. The aim of this study was to assess the microbiological quality of carrot slices after
treatment with aqueous extracts of Lobularia maritima (AELm) at different concentrations AELm1
(10 mg/mL), AELm2 (5 mg/mL), AELm3 (2.5 mg/mL) and AELm4 (1.25 mg/mL), and Salmonella
enterica subsp. enterica serovar Enteritidis, along with vacuum packaging and storage of carrots
for 7 days at 4 ◦C. On days 1. and 7., total viable counts (TVC), and coliforms bacteria (CB), and
Salmonella count were all analysed. Microorganisms that were obtained from carrots were
identified using MALDI-TOF MS Biotyper Mass Spectrometry. The total viable, coliform bacteria
and Salmonella counts were varied by the group of treatment. Higher counts were found in the
control group on both days. The most isolated species of bacteria were Salmonella enterica and
Pantoea agglomerans on the 1. day and Klebsiella oxytoca on the 7. day. The current study adds
useful information for a better understanding of how Salmonella enterica reacts to the effect of
AELm and its potential use as a sustainable washing method to eliminate bacteria from freshly cut
carrots.
The experiment was conducted to developed a methodology for preservation of minimally processed fresh-cut carrot pieces using sixteen treatment combinations comprised of four levels of potassium sorbate treatment [0 ppm (K1), 500 ppm (K2), 1000 ppm (K3) and 1500 ppm (K4)] and four levels of UV radiation time treatment [without UV radiation treatment (T1), 15 min (T2), 30 min (T3) and 45 min (T4)]. The result of present investigation indicated that minimally processed fresh-cut carrot pieces can be prepared by pre-treating pieces with 1000 ppm potassium sorbate followed by UV radiation treatment of packed pieces for 30 minutes and can remain shelf stable on the basis of nutritional as well as sensory quality up to ten days storage in polypropylene bag of 400 gauge. The cost of production per 100 g pack of minimally processed fresh-cut carrot pieces was worked out Rs. 16.01. Thus, prepared product can commercially be explored by food processing industry to ensure better returns to growers, processors and consumers as well.
Lactic acid bacteria (LAB) cause quality deterioration including acidification and production of off-flavor components in food. To rapidly detect LAB, a lateral flow immunochromatographic assay (LFIA) was developed. An antibody (Ab) was obtained using Lactiplantibacillus plantarum as an immunogen, and the LFIA was performed based on this Ab. This showed positive reactions with LAB and a wide range of Gram-positive bacteria. An acid producing ability test using a semiconductor pH sensor was performed in combination with the LFIA. The bacteria testing positive in both the pH test (pH-positive) and the LFIA (LFIA-positive) were LAB. Twenty-three species of LAB in 13 genera could be detected specifically. Fresh foods and their equivalent spoiled foods were cultured for 0, 12, and 24 h, and the time required for the cultures to show LFIA-positive and pH-positive results was investigated. Of the 51 foods, 42 showed shorter culture times for the spoiled food than for the fresh food (spoilage detection rate: 82%). Amplicon analysis detected LAB including Leuconostoc citreum and Leuconostoc gelidum in spoiled foods. As this novel method can detect LAB in approximately 1 h, its use should make it possible to judge the freshness of food before shipping or sale.
Carbon dioxide is effective for extending the shelf-life of perishable foods by retarding bacterial growth. The overall effect of carbon dioxide is to increase both the lag phase and the generation time of spoilage microorganisms; however, the specific mechanism for the bacteriostatic effect is not known. Displacement of oxygen and intracellular acidification were possible mechanisms that were proposed, then discounted, by early researchers. Rapid cellular penetration and alteration of cell permeability characteristics have also been reported, but their relation to the overall mechanism is not clear. Several researchers have proposed that carbon dioxide may first be solubilized into the liquid phase of the treated tissue to form carbonic acid (H2CO3), and investigations by the authors tend to confirm this step, as well as to indicate the possible direct use of carbonic acid for retarding bacterial spoilage. Most recently, a metabolic mechanism has been studied by a number of researchers whereby carbon dio...
Surveys were made of commercial processing lines used to prepare fresh-cut vegetables such as chopped salad ingredients, carrot sticks, and cauliflower florets. Washing and chlorinated water dips only partially removed the microorganisms that were intrinsic to the vegetables. Major sources of in-plant contamination were the shredders used to prepare chopped lettuce and coleslaw. Gram-negative rods were the predominant microflora with species of Pseudomonas being most numerous; many were psychrotrophic. Only low numbers of lactic acid bacteria and fungi were recovered. Copyright © International Association of Milk, Food and Environmental Sanitarians.
Modified-atmosphere packaged (MAP) foods have become increasingly more common in North America, as food manufacturers have attempted to meet consumer demands for fresh, refrigerated foods with extended shelf life. Although much information exists in the general area of MAP technology, research on the microbiological safety of these foods is still lacking. The great vulnerability of MAP foods from a safety standpoint is that with many modified atmospheres containing moderate to high levels of carbon dioxide, the aerobic spoilage organisms which usually warn consumers of spoilage are inhibited, while the growth of pathogens may be allowed or even stimulated. In the past, the major concerns have been the anaerobic pathogens, especially the psychrotrophic, nonproteolytic Clostridia. However, because of the emergence of psychrotrophic pathogens such as Listeria monocytogenes, Aeromonas hydrophila, and Yersinia enterocolitica, new safety issues have been raised. This stems mainly from the fact that the extended shelf life of many MAP products may allow extra time for these pathogens to reach dangerously high levels in a food. This review focuses on the effects of MAP on the growth and survival of foodborne pathogens. Considered are the major psychrotrophic pathogens, the mesophiles such as the salmonellae and staphylococci, as well as the microaerophilic Campylobacter jejuni. The use of MAP in various food commodities such as beef, chicken, fish, and sandwiches is also discussed. Examples of various foods currently being packaged under MAP in North America are given, along with the specific atmospheres employed for the various food groups. Major safety concerns that still need to be addressed include the potential for growth and toxin production of Clostridium botulinum type E in MAP fish products, the growth of L. monocytogenes and A. hydrophila under modified atmospheres in various food commodities, and the enhanced survival of anaerobic spores and C. jejuni under certain gas atmospheres. Additional research with MAP foods is needed to ensure the microbiological safety of the numerous MAP products that will be available to the consumer in the next decade and beyond. Copyright © International Association of Milk, Food and Environmental Sanitarians.
Foods are perishable by nature. Numerous changes take place in foods during processing and storage. It is well known that conditions used to process and store foods may adversely influence the quality attributes in foods. Upon storage for a certain period, one or more quality attributes of a food may reach an undesirable state. At that instant, the food is considered unsuitable for consumption and it is said to have reached the end of its shelf life. In this chapter, certain major modes of food deterioration will be examined. These modes of deterioration will be expressed mathematically as rate equations. Reaction kinetics and various models that are used in practice to express quality changes in foods will be discussed. At the end of the chapter, a brief discussion of sensors that indicate time and temperature exposures of foods and their use in monitoring shelf life of foods will be presented.
The Arrhenius Law, which was originally proposed to describe the temperature dependence of the specific reaction rate constant in chemical reactions, does not adequately describe the effect of temperature on bacterial growth. Microbiologists have attempted to apply a modified version of this law to bacterial growth by replacing the reaction rate constant by the growth rate constant, but the modified law relationship fits data poorly, as graphs of the logarithm of the growth rate constant against reciprocal absolute temperature result in curves rather than straight lines. Instead, a linear relationship between in square root of growth rate constant (r) and temperature (T), namely, square root = b (T - T0), where b is the regression coefficient and T0 is a hypothetical temperature which is an intrinsic property of the organism, is proposed and found to apply to the growth of a wide range of bacteria. The relationship is also applicable to nucleotide breakdown and to the growth of yeast and molds.
Four cultivars of asparagus (Asparagus officinalis L. ‘Mary Washington 500W’, ‘Limbras 18’ ‘Rutgers Beacon’, and ‘Jersey Giant’) were harvested from a single site and stored at 1°C for up to three weeks in air and controlled atmosphere (CA; 7% O2, 7% CO2). All cultivars stored well but shelf-life was reduced with increasing storage time in both air and CA. Water loss alone did not appear to be responsible for the reduction in shelf-life. CA significantly increased shelf-life. ‘Jersey Giant’ had a significantly longer shelf-life than the other three cultivars.