No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Pulsed Ligh inactivation of Listeria innocua on food packaging materials of different surface roughness and reflectivity
Abstract
Inactivation of Listeria innocua on food packaging materials by Pulsed Light (PL) treatment was investigated. Coupons of low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene-laminated ultra-metalized polyethylene terephthalate (MET), polyethylene-coated paperboard (TR), and polyethylene-coated aluminum foil paperboard laminate (EP) were inoculated with L. innocua cells in stationary growth phase. Inoculated coupons (∼8 CFU/coupon) were treated with Pulsed Light fluence of up to 8.0 J/cm2, and survivors were determined. Reductions up to 7.2 ± 0.29, 7.1 ± 0.06, 4.4 ± 0.85, 4.5 ± 1.32, and 3.5 ± 0.82 log CFU/coupon were obtained on LDPE, HDPE, MET, TR, and EP, respectively. Inactivation data were used to determine Weibull kinetic parameters and predict inactivation in a wide range of fluence. Increasing surface reflectivity and surface roughness appeared to induce lower inactivation. Minimal surface heating was observed for all materials except MET, on which significant heating occurred. These results demonstrate the potential of Pulsed Light as an effective method for decontaminating food packaging materials.
... The reduction of viable cells on surfaces after PL treatment depends on the degree of surface roughness defects of the materials. When the surface roughness of materials, such as polyethylene-coated paperboard (TR), polyethylene-laminated ultra-metalized polyethylene terephthalate (MET), and polyethylene-coated aluminum foil paperboard laminate (EP) reach the micrometer range, the defect areas in the surfaces could harbor one or multiple layers of cells and prevent direct PL treatment (Ringus and Moraru, 2013). This phenomenon, which is called the "shading effect," could cause a dead area of sterilization and greatly diminish the efficiency of PL treatment (Chen et al. 2015). ...
... However, the UV transmission rate does not seem to be the only important factor for PL inactivation. Ringus and Moraru (2013) examined the PL treatment efficiency of a direct LDPE (0.04 mm in thickness) surface and the reverse side of an LDPE surface. Ten drops of 50 mL bacterial suspension containing 2 x 10 9 CFU were inoculated on the surface of LDPE and treated with fluences of 2, 4, 6, and 8 J/cm 2 . ...
... One possible explanation for this observation was that the fluence required to inactivate L. innocua was low and could be achieved through an LDPE film with a 20% UV transmission rate. Another explanation was that the compositions of the LDPE used in the studies of Keklik et al. (2010) and Ringus and Moraru (2013) were not the same, and they had different UV transmission rates. ...
... A close examination of the scientific literature shows that until now in-package treatment is more or less the stage of a feasibility study. Examples of reported facts are the polymer used, thickness of the material, light transmittance, supplier and product name (Fernández et al., 2009;Ganan, Hierro, Hospital, Barroso, & Fernández, 2013;Haughton et al., 2011;Hierro et al., 2011Hierro et al., , 2012Keklik, Demirci, & Puri, 2009Ramos-Villarroel, Aron-Maftei, Martín-Belloso, & Soliva-Fortuny, 2012a, 2012bRingus & Moraru, 2013). Hardly any of the authors, however, report more details like the additives and production process, possible laminates or co-extrudates and the properties of the individual layers or factors like roughness or reflectivity, which all could influence the efficacy of the decontamination. ...
... Further, Ringus and Moraru (2013) reported that treatment of a low-density PE film coupon (40 μm) inoculated with Listeria innocua yields in the same decontamination (7 log CFU per coupon) whether treated with the inoculated surface to the PL source or upside down (Table 1). ...
... Next to the surface decontamination of packaging materials and the link to material properties, Ringus and Moraru (2013) investigated the change in structural and physical properties of surface-treated lowand high-density polyethylene (LDPE and HDPE) as well as three laminates, namely MET, TR and EP. In their work, the water contact angle measurement was used as a measure of surface hydrophobicity to indicate changes in surface structure, barrier property and bacterial adherence (Bower, McGuire, & Daeschel, 1996;Dury-Brun, Chalier, Desorby, & Voilley, 2007;Li & Logan, 2005;Mafu, Roy, Goulet, & Savoie, 1991;Raab, Kotulák, Kolařík, & Pospíšil, 1982). ...
Non-thermal processes have become increasingly popular over the last decades. As one of the emerging non-thermal technologies, pulsed light (PL) represents a fast, tailored and residue-free technology that - via high frequency, high intensity pulses of broad-spectrum light rich in the UV fraction - is capable of inactivating microbial cells and spores. This review provides some updated information on PL and its suitability for surface decontamination of solid matrices such as food and food-contact materials. The focus is on post-packaging application, which allows treatment of the packaged food thus avoiding undesirable recontamination. Furthermore, prerequisites for in-package application, the efficacy of the treatment compared with the non-packaged pendant and the alteration of both the product and packaging material accomplished by PL are discussed. In the case of packaging material, not only physical stability and mechanical stability but also chemical migration and possibly arising safety concerns are highlighted. Industrial relevance This review offers a comprehensive survey of the use of pulsed light for the decontamination of unpackaged as well as packaged solid foods and associated food contact materials. Based on this background, food scientists as well as research and development can develop suited packaging concepts and optimize the treatment with regard to decontamination efficiency, product quality and safety.
... It is evident from the literature that the presence of organic materials may provide microbial cells with more resistance to UV-light mediated disinfection [37] or other chemical disinfectants [36], which may partially explain why bacterial cells attached to lettuce may exhibit higher resistance to PUV treatment. Moreover, PUV treatment is a light-mediated intervention; therefore, the optical transparency and reduced surface roughness of the packaging film may also effect inactivation, as previously reported [38]. ...
... across all the treatment conditions tested. The temperature data collected in the current study are well within the range of several previously reported studies [8,38,[53][54][55][56][57][58]. The results of the current study, in conjunction with the previous studies mentioned above, indicate that the increase in temperature resulting from PUV treatment is dependent on several factors, such as distance from the UV source to the target sample, frequency and duration of pulses, energy levels or fluences, and food or target surface type. ...
... The results of the current study, in conjunction with the previous studies mentioned above, indicate that the increase in temperature resulting from PUV treatment is dependent on several factors, such as distance from the UV source to the target sample, frequency and duration of pulses, energy levels or fluences, and food or target surface type. The results from previous studies indicated that a UV-source-to-sample distance of approximately 10 cm may be used to avoid excessive heating during PUV light treatments [38,56,59]. ...
The inactivation of biofilms formed by pathogenic bacteria on ready-to-eat and minimally processed fruits and vegetables by nonthermal processing methods is critical to ensure food safety. Pulsed ultraviolet (PUV) light has shown promise in the surface decontamination of liquid, powdered, and solid foods. In this study, the antimicrobial efficacy of PUV light treatment on nascent biofilms formed by Escherichia coli O157:H7 and Listeria monocytogenes on the surfaces of food packaging materials, such as low-density polyethylene (LDPE), and fresh produce, such as lettuce (Lactuca sativa) leaves, was investigated.
The formation of biofilms on Romaine lettuce leaves and LDPE films was confirmed by crystal violet and Alcian blue staining methods. Inactivation of cells in the biofilm was determined by standard plating procedures, and by a luminescence-based bacterial cell viability assay. Upon PUV treatment of 10 s at two different light source to sample distances (4.5 and 8.8 cm), viable cell counts of L. monocytogenes and E. coli O157:H7 in biofilms on the lettuce surface were reduced by 0.6-2.2 log CFU mL(-1) and 1.1-3.8 log CFU mL(-1), respectively. On the LDPE surface, the efficiency of inactivation of biofilm-encased cells was slightly higher. The maximum values for microbial reduction on LDPE were 2.7 log CFU mL(-1) and 3.9 log CFU mL(-1) for L. monocytogenes and E. coli O157:H7, respectively. Increasing the duration of PUV light exposure resulted in a significant (P < 0.05) reduction in biofilm formation by both organisms. The results also revealed that PUV treatment was more effective at reducing E. coli biofilms compared with Listeria biofilms. A moderate increase in temperature (~7-15°C) was observed for both test materials.
PUV is an effective nonthermal intervention method for surface decontamination of E. coli O157:H7 and L. monocytogenes on fresh produce and packaging materials.
... In bacterial spores, UV-C treatment mainly results in the formation of the ''spore photoproduct'' 5-thyminyl-5,6-dihydrothymine, and singlestrand breaks, double-strand breaks, and cyclobutane pyrimidine dimers (Demirci & Krishnamurthy, 2011). Ringus and Moraru (2013) hypothesized that the physical properties of the surfaces to be treated, including surface topography and reflectivity, affect the efficacy of PL inactivation. Surface roughness and crevices have been suggested to shield microbial cells during treatment; and surface hydrophobicity may influence the distribution of bacterial contaminants on surfaces, as liquid droplets may contain hydrophilic organisms. ...
... SEM images of these stainless steel surfaces showed that cells congregated in the defect areas of these surfaces, which could be a potential problem for PL decontamination. Ringus and Moraru (2013) compared the ten-point roughness values of five different packaging material surfaces and the reduction of viable cells after PL treatment. When the surface roughness of the materials, such as polyethylenelaminated ultra-metalized polyethylene terephthalate (MET), polyethylene-coated paperboard (TR), and polyethylene-coated aluminum foil paperboard laminate (EP), reached the micrometer range, the defect areas in the surfaces could harbor one or multiple layers of cells and prevent direct PL treatment. ...
... Woodling and Moraru (2005) proposed that surfaces with a high degree of reflectivity might decrease the light absorption of the inoculum and lead to poor inactivation. The same phenomenon was also reported by Ringus and Moraru (2013). They observed that packaging materials, which had high specular and diffuse reflections, such as MET, EP, and TR, had lower PL inactivation (3.5-4.5 log reductions) compared to 7.1-7.2 ...
... UV-C light has been used to decontaminate air and water as well as a wide variety of contact surfaces and materials (Haughton, Lyng, Cronin, et al., 2011;Koutchma, 2014). PL has also proven effective in the decontamination of a large number of surfaces (Ringus & Moraru, 2013;Woodling & Moraru, 2005), packaging materials (Haughton, Lyng, Morgan, et al., 2011;Turtoi & Nicolau, 2007) and even liquids (Birmpa, Vantarakis, Paparrodopoulos, Whyte, & Lyng, 2014). Both technologies have also demonstrated their efficacy for food surface decontamination (Fan, Huang, & Chen, 2017;Gómez-López, Ragaert, Debevere, & Devlieghere, 2007;Heinrich, Zunabovic, Bergmair, Kneifel, & Jäger, 2015). ...
... These differences between technologies also occurred at similar doses and could be attributed to characteristics of the SS, the light technologies, or a combination of both. SS surfaces can have some defect areas, with different degrees of roughness, and these areas can allow cells to congregate in single or multiple layers which could reduce the efficacy of the light treatments (Ringus & Moraru, 2013;Woodling & Moraru, 2005). However, this may not explain the higher inactivation levels achieved with PL on SS. ...
The decontamination effect of two light-based technologies on salmon, polyethylene (PE) and stainless steel (SS) was evaluated. Optimization of treatment conditions for ultraviolet light (UV-C) and pulsed light (PL) was carried out on raw salmon, obtaining inactivation levels of 0.9 and 1.3 log CFU/g respectively. The effects of treatments on several microbial groups present in salmon were then evaluated. For both technologies, Pseudomonas spp. were found to be the most resistant group of microorganisms tested. Three different strains from within this group were isolated and speciated, including a P. fluorescens strain which was selected for subsequent studies. PE and SS surfaces were inoculated with a suspension of the P. fluorescens suspended in a ‘salmon juice’ solution, and treated with UV-C and PL at different doses (mJ/cm²). PE surfaces were effectively decontaminated a low doses for both technologies, with a reduction of >4 log cycles observed. Decontamination of SS was also effective when treated with PL, although at higher doses than for PE. When SS was treated with UV-C, the maximum reduction of P. fluorescens achieved was 2 log cycles, even at the highest dose.
... (23) The authors also speculate that more reflective surfaces may decrease the dose of light absorbed by bacteria contributing to reduced inactivation. (23) Ringus and Moraru (24) demonstrated that Listeria innocua inactivation was decreased on relatively more reflective and rough surfaces (all coated with polypropylene) using pulsed light. (24) Complexities in bacterial inactivation based on surface topography (i.e. ...
... (23) Ringus and Moraru (24) demonstrated that Listeria innocua inactivation was decreased on relatively more reflective and rough surfaces (all coated with polypropylene) using pulsed light. (24) Complexities in bacterial inactivation based on surface topography (i.e. roughness or smoothness) and reflectivity may have been exhibited in this study. ...
The estimated 721,800 hospital acquired infections per year in the United States have necessitated development of novel environmental decontamination technologies such as ultraviolet germicidal irradiation (UVGI). This study evaluated the efficacy of a novel, portable UVGI generator (the TORCH™, ChlorDiSys Solutions, Inc., Lebanon, NJ) to disinfect surface coupons composed of plastic from a bedrail, stainless steel, chrome-plated light switch cover, and a porcelain tile that were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus faecalis (VRE). Each surface type was placed at 6 different sites within a hospital room and treated by 10-minute ultraviolet-C (UVC) exposures using the TORCH™ with doses ranging from 0 to 688mJ/cm(2) between sites. Organism reductions were compared with untreated surface coupons as controls. Overall, UVGI significantly reduced MRSA by an average of 4.6 log10 (GSD: 1.7 log10, 77% inactivation, p<0.0001) and VRE by an average of 3.9 log10 (GSD: 1.7 log10, 65% inactivation, p<0.0001). MRSA on bedrail was reduced significantly (p<0.0001) less than on other surfaces, while VRE was reduced significantly less on chrome (p = 0.0004) and stainless steel (p = 0.0012) than porcelain tile. Organisms out of direct line of sight of the UVC generator were reduced significantly less (p<0.0001) than those directly in line of sight. UVGI was found an effective method to inactivate nosocomial pathogens on surfaces evaluated within the hospital environment in direct line of sight of UVGI treatment with variation between organism and surface types.
... The microbicidal effect of PL treatment is primarily attributed to the UV portion of its spectrum that causes formation of pyrimidine dimers within the bacterial DNA, which block DNA transcription and replication, ultimately leading to cell death (Wang et al., 2005;Elmnasser et al., 2007;Woodling and Moraru, 2007;Kramer and Muranyi, 2014). Several studies have shown that PL can effectively inactivate microorganisms on various foods and food contact surfaces, including 2-log reduction of L. innocua on fresh-cut mushrooms (Ramos-Villarroel et al., 2012), 2-to 4.5-log reduction of E. coli in apple juice (Sauer and Moraru, 2009;Palgan et al., 2011), 1-log reduction of Salmonella Typhimurium on beef and tuna carpaccio (Hierro et al., 2012), and >7-log reduction of L. innocua on low density polyethylene (Ringus and Moraru, 2013). ...
... The potential of PL to be used on packaging materials and on packaged foods has been investigated before. Ringus and Moraru (2013) reported that PL treatment of L. innocua through transparent LDPE packaging was as effective as when applied directly on the inoculated side of the packaging material. Fernández et al. (2009) reported that PL consistently achieved the same degree of inactivation of L. monocytogenes on inoculated agar either unwrapped or wrapped in polyethylene, polyamide/polyethylene/vinyl acetate co-polymer, or polyamide/polyethylene copolymer. ...
Cheese products are susceptible to postprocessing cross-contamination by bacterial surface contamination during slicing, handling, or packaging, which can lead to food safety issues and significant losses due to spoilage. This study examined the effectiveness of pulsed-light (PL) treatment on the inactivation of the spoilage microorganism Pseudomonas fluorescens, the nonenterohemorrhagic Escherichia coli ATCC 25922 (nonpathogenic surrogate of Escherichia coli O157:H7), and Listeria innocua (nonpathogenic surrogate of Listeria monocytogenes) on cheese surface. The effects of inoculum level and cheese surface topography and the presence of clear polyethylene packaging were evaluated in a full factorial experimental design. The challenge microorganisms were grown to early stationary phase and subsequently diluted to reach initial inoculum levels of either 5 or 7 log cfu/slice. White Cheddar and process cheeses were cut into 2.5×5 cm slices, which were spot-inoculated with 100 µL of bacterial suspension. Inoculated cheese samples were exposed to PL doses of 1.02 to 12.29 J/cm(2). Recovered survivors were enumerated by standard plate counting or the most probable number technique, as appropriate. The PL treatments were performed in triplicate and data were analyzed using a general linear model. Listeria innocua was the least sensitive to PL treatment, with a maximum inactivation level of 3.37±0.2 log, followed by P. fluorescens, with a maximum inactivation of 3.74±0.8 log. Escherichia coli was the most sensitive to PL, with a maximum reduction of 5.41±0.1 log. All PL inactivation curves were nonlinear, and inactivation reached a plateau after 3 pulses (3.07 J/cm(2)). The PL treatments through UV-transparent packaging and without packaging consistently resulted in similar inactivation levels. This study demonstrates that PL has strong potential for decontamination of the cheese surface.
... The delay in the rate of diffusion of polymer matrices allows the food to keep longer its organoleptic properties, increasing the shelf life and consumer food safety [2]. The nanoparticles used in the production of FP are polymeric materials with improved barrier properties to extend the shelf life of food, isolating from organic vapors or substances such as oxygen, carbon dioxide and aromas [3]. ...
... The equation that estimates the mass transfer of the migrant by molecular diffusion, according to Fick´s law through the polymer matrix is: In the interphase. there is the partition coefficient of the migrant in equilibrium represented by: (2) Lastly, the transfer through the boundary layer in the simulant phase at the vicinity of the interphase is described by: (3) Where. is the mass transfer coefficient that cuantifies the natural convection in the simulant phase [m/s] and is the migrant within the food simulant [kg/m 3 ]. ...
Monitoring the phenomenon of migration of an Antimicrobial Agent (AA), by means of a detection model using wireless nanosensory networks (WNSNs), is a new methodology required in the technological development of intelligent packaging. The detection models are programmed using the MATLAB simulation tool. Each nanosensor will give a migration value which is averaged for the analysis, transmitting and visual communication on a scale of colors, migration values depend on the initial concentration of AA in the polymer matrix and the state of the container. By an extrusion processs, a laminar phyllosilicate is physically mixed at high temperatures with a one low density polyethylene matrix (LDPE), polyolefin is one of the most used, forming a polymer clay nanocomposite (NPA). This new material presents improved barrier properties that delay the damage in time caused by external agents. The NPA are treated by a process of impregnation with CO2 as supercritical fluid (SCF) in which Thymol is solubilized, with the objective of introducing an AA into the NPA that migrates in time and is solubilized in foods, postponing deterioration reactions by the effect of decomposing microorganisms.
... As for the organoleptic properties of the various products, food contact surfaces like packaging films are affected by the treatment according to the prevalent conditions. Parameters analyzed in the studies (Table 4) are: elastic modulus, yield strength, and percent elongation at yield point, maximum tensile strength, percent elongation at break and hydrophobicity (Keklik, 2009;Keklik et al., 2009;Ringus and Moraru, 2012). ...
... While in vitro tests spotlight microbial reductions of up to 6 Log on solid media, it has been shown that the more complex the supporting medium in terms of structure and composition is, the less inactivation can be expected. Hence, even the decontamination of relatively simple appearing food-contact surfaces like plastic packaging materials (Table 4) show approximately halving of the decontamination efficiency depending on the material characteristics (Ringus and Moraru, 2012). ...
Abstract Today, the increasing demand for minimally processed foods that are at the same moment nutritious, organoleptically satisfactory and free from microbial hazards challenges the research and development to establish alternative methods to reduce the level of bacterial contamination. As one of the recent emerging non-thermal methods, pulsed light (PL) constitutes a technology for the fast, mild and residue-free surface decontamination of food and food contact materials in the processing environment. Via high frequency, high intensity pulses of broad-spectrum light rich in the UV fraction, viable cells as well as spores are inactivated in a non-selective multi-target process that rapidly overwhelms cell functions and subsequently leads to cell death. This review provides specific information on the technology of pulsed light and its suitability for unpackaged and packaged meat and meat products as well as food contact materials like production surfaces, cutting tools and packaging materials. The advantages, limitations, risks and essential process criteria to work efficiently are illustrated and discussed with relation to implementation on industrial level and future aspects. Other issues addressed by this paper are the need to take care of the associated parameters such as alteration of the product and utilized packaging material to satisfy consumers and other stakeholders.
... Different studies have shown that PL can provide a remarkable degree of microbial inactivation on the surface of a number of foods, such as raw fish and meat (Keklik, Demirci, & Puri, 2010;Ozer & Demirci, 2006), meat products (Ganan, Hierro, Hospital, Barroso, & Fernández, 2013;Hierro et al., 2011;Keklik, Demirci, & Puri, 2009), eggs (Hierro, Manzano, Ordóñez, Hoz, & Fernández, 2009) and vegetables (Gómez-López et al., 2005), and also liquids such as milk (Krishnamurthy, Demirci, & Irudayaraj, 2007) and fruit juices (Pataro et al., 2011), where cells are not only on the surface. Studies have also been carried out on packaging materials (Ringus & Moraru, 2013). ...
... To predict that, mathematical models derived from quantitative studies on microbial populations are a useful tool. Some studies have been carried out by modelling inactivation as a function of fluence, inoculum size, surface roughness and reflectance (Izquier & Gómez-López, 2011;Ringus & Moraru, 2013;Uesugi, Woodling, & Moraru, 2007). However, no models have been established up to date to describe the relationship between microbial inactivation and some characteristics such as the colour of the substrate and the penetration of light. ...
... In infant powder milk, PL treatment at 10, 15, 20 and 25kV for 5000, 600, 300 and 100μs inactivated the L. monocytogenes by 4-5 log reduction ( Choi et al., 2010 ). Ringus and Moraru (2013) reported that intense pulse light treatment (0.67 J/cm 2 ) reduced the L.innocua from LDPE (1.9-7.1 log) and HDPE (1.9-7.2 log) packaging material. The numerous different approaches of PL on food items make it a better non-thermal processing method for the production of improved quality of PL treated products for commercial applications. ...
Emerging non-thermal technologies for enhancing shelf life and food safety have revolutionized the food processing sector. Adopting different non-thermal techniques like supercritical carbon dioxide, high hydrostatic pressure, cold plasma, and ozone technology can improve food quality and enhance the storage life of foods by reducing spoilage and wastage. Evidence shows that these emerging innovative technologies not only ensure the freshness of the food but also keep the nutritionally heat-sensitive materials intact in the foods. Moreover, these can serve as alternatives to conventional heat processing methods resulting in hygienic and safe foods, retention of bioactive compounds, decontamination of microorganisms, and limited changes in the nutritional and sensory attributes. In this review, the basic principles of non-thermal technologies and their effect on the quality parameters of foods are reported. Also, the potential applications and benefits of these technologies as alternative processes for food preservation and to eliminate contamination and infection from food samples are discussed.
... Roughness determined for chitosan films was similar to that for LDPE and HDPE. For instance, the Ra of PVA film was determined as 10.05 nm [27]. The results obtained in the present study showed that the addition of phenolic acids decreases the roughness parameters. ...
Chitosan-based films are promising for consideration as packaging materials. In this study, we modified the chitosan by phenolic acid addition, such as ferulic acid, caffeic acid, tannic acid, and gallic acid. The mechanical and thermal properties were studied, and the water vapor permeability rate was determined. Moreover, the antioxidant activity and film color were considered. The results showed that phenolic acids are effective cross-linkers for chitosan. The addition of phenolic acids improved the mechanical properties and decreased the roughness of surfaces. The enthalpy value was lower for films with phenolic acids than for pure chitosan. Chitosan with ferulic acid showed the highest antioxidant activity and water permeability value. Based on the obtained results, we determined that films obtained from the chitosan/ferulic acid mixture are the most promising for use as packaging material.
... The hydrophobicity of the food surface may affect the distribution of microbial cells promoting the formation of cell clusters and reducing PL inactivation. Furthermore, a high surface reflectivity, causing a decreased light absorption of the microbial cells, could lead to poor inactivation [229,230]. ...
The application of edible coatings (EC) in combination with pulsed light (PL) treatments represents an emerging approach for extending the shelf life of highly perishable but high value-added products, such as fresh-cut fruits and vegetables. The surface of these products would benefit from the protective effects of ECs and the PL decontamination capability. This review describes in detail the fundamentals of both EC and PL, focusing on the food engineering principles in the formulation and application of EC and the delivery of efficient PL treatments and the technological aspects related to the food characterization following these treatments and discussing the implementation of the two technologies, individually or in combination. The advantages of the combination of EC and PL are extensively discussed emphasizing the potential benefits that may be derived from their combination when preserving perishable foods. The downsides of combining EC and PL are also presented, with specific reference to the potential EC degradation when exposed to PL treatments and the screening effect of PL transmittance through the coating layer. Finally, the potential applications of the combined treatments to food products are highlighted, comparatively presenting the treatment conditions and the product shelf-life improvement.
... PL processing can be described as a sterilization or decontamination method used primarily in food surfaces, [6,7] packaging material, [8] and surface equipment. [9] This technology applies concentrated light energy exposing the sample to intense pulses of light. ...
Currently, there is a necessity for new technologies that are less harmful to the environment. Consumers have become increasingly demanding towards the quality of the processed products they consume as well as their environmental impact. Pulsed light (PL) technology is a green technology capable of maintaining food quality and safety without impairing nutritional value. PL has been used in the treatment of different food and its constituents. This mini-review aims to describe the basic principle of PL functioning as well as provide examples of the newest applications in the food industry.
... However, our results demonstrated that laminated packaging blocks the passage of ultraviolet rays by 100%, even at the highest UV-C dose (0.1001±0.01 J/cm 2 ) ( Table 1). This phenomenon may be due to reflectance from the lamination of the packaging, where the incident radiation is equal to reflected radiation, hindering or even preventing the passage of UV-C rays [33,34,35]. In this context, laminated packaging should not be used for products to be subjected to the process of UV-C radiation. ...
The current study investigated the effectiveness of shortwave ultraviolet (UV-C) radiation on rainbow trout fillets inoculated with Proteus mirabilis when combined with Modified Atmosphere Packaging technology (MAP). Rainbow trout were inoculated, packaged under different ratios of CO 2 and N 2 gases and subjected to UV-C radiation. Our study model demonstrated that at least 0.1001 J/cm 2 is necessary to significantly reduce Proteus mirabilis loads (reduction of 1.8 log CFU.g-1) in trout fillet packaged without CO 2 gas barrier. The rainbow trout fillet packaged with CO 2 gas barrier had significantly reduced Proteus mirabilis load but not when associated with UV-C radiation exposure. The combined effect of UV-C and MAP at different radiation doses and ratios of CO 2 and N 2 gas did not contribute to Proteus mirabilis growth reduction. Overall, the use of MAP significantly reduces the penetration and effect of UV-C radiation when compared to the unpackaged control. The combination of these two technologies of food preservation does not seem to be a suitable model to extend the shelf life of packaged fish fillet.
... The shadow effect will then generate a tail in the inactivation curve because part of the microbial population will never be reached by light. In solids, microorganisms can be shielded by surface features such as the achnes of strawberries or the druplets of raspberries (Bialka et al., 2008) or by surface irregularities of food contact surfaces (Ringus & Moraru, 2013). In liquids, turbidity and suspended solids area main obstacles for microbial inactivation although appropriate mixing can maximize the exposure to light of all microorganisms present in the liquid mass (G omez-L opez, Koutchma, & Linden, 2012). ...
Pulsed light (PL) is an emerging technology that has attracted attention by food scientists due to the desirable combination of energy-efficiency and capacity to achieve extremely fast microbial inactivation performances. PL-mediated microbial inactivation curves have been reported previously by many researchers built on culture-based methods. However, an increasing amount of literature has recently shown that PL can induce microbial cells to enter a viable but non-culturable (VBNC) state, which raises concerns over interpreting data from previously-published microbial inactivation studies and compels scientists to explore alternative or complementary use of other more appropriate approaches to determine microbial inactivation. It is envisaged that the coming years will be seen as a transition period where previously-published microbial culture-based kinetic studies will be re-analyzed from the point of view of applying new lethality indicators that will either confirm or modify our thoughts about the inactivation kinetics by PL as current state-of-the-art knowledge in this area only uses data generated by microbial culture-based methods. The present chapter presents an overview of the VBNC state in this context and constitutes the first attempt to identify suitable alternative indicators of PL-mediated microbial lethality. Specifically, it describes the battery of approaches that could possibly be used to address this VBNC issue along with reporting on the efficacy and appropriates of using different microbial kinetic death rate models for PL-treatments and its interpretation. It is envisaged that the information described in this chapter will impact positively on the food industry in the future.
... On the other hand, the reflectance and roughness of PL treated plastic surfaces has been shown to affect PL effectiveness. Highly reflective and rough surfaces result in lower inactivation of L. innocua compared to smooth and less reflective surfaces (Ringus et al. 2013). Similar results were also obtained by Woodling and Moraru (2005) who investigated the PL efficiency on different types of stainless steel surfaces. ...
Non-thermal disinfection technologies are gaining increasing interest in the field of minimally processed food in order to improve the microbial safety or to extend the shelf life. Especially fresh-cut produce or meat and fish products are vulnerable to microbial spoilage but due to their sensitivity, they require gentle preservation measures. The application of intense light pulses (PL) of a broad spectral range comprising ultraviolet, visible and near infrared irradiation is currently investigated as a potentially suitable technology to reduce microbial loads on different food surfaces or in beverages. Considerable research has been performed within the last two decades, in which the impact of various process parameters or microbial responses as well as the suitability of PL for food applications has been examined. This review summarizes the outcome of the latest studies dealing with the treatment of various foods including the impact of PL on food properties as well as recent findings about the microbicidal action and relevant process parameters. This article is protected by copyright. All rights reserved.
... For solid substrates, microorganisms may lodge in surface irregularities or penetrate into the solid beyond PL's penetration depth, limiting the microorganisms' exposure to PL (Woodling & Moraru, 2005). For instance, high UV reflectivity was found to reduce inactivation on Al packaging materials (Ringus & Moraru, 2013). ...
This study investigated the effect of sublethal temperatures on the efficacy of Pulsed Light (PL) treatment for the inactivation of Listeria innocua, Escherichia coli ATCC 25922, and Pseudomonas fluorescens. A thin layer of clear, liquid phosphate buffer inoculated with one of the challenge organisms, at a concentration of about 10⁸ CFU/mL, was equilibrated to a temperature ranging from 5 °C to 50 °C and then treated with PL, at doses between 1.02 and 12.29 J/cm². All treatments were performed in triplicate. In the temperature range of 5 °C to 40 °C, the average maximum reductions for L. innocua, E. coli, P. fluorescens were 6.27 ± 0.23 log CFU, 6.66 ± 0.36 log CFU, and 6.15 ± 0.19 log CFU, respectively. Temperature did not affect PL inactivation of E. coli or P. fluorescens, but a modest synergistic effect between PL and temperature was observed for L. innocua treated above 40 °C.
... For instance, Woodling and Moraru (2005) found lower PL inactivation of L. innocua on electropolished, highly reflective stainless steel than on less reflective stainless steel coupons. These results have been also confirmed by the finding of Ringus and Moraru (2013), who compared microbial inactivation of Listeria innocua on food packaging materials with different surface properties. In particular, coupons of LDPE, HDPE, MET, TR, and EP inoculated (8 CFU/coupon) with L. innocua cells were treated with PL fluence of up to 8.0 J/cm 2 . ...
The application of pulsed light (PL) to foods has gained increasing interest, from both the research world and food processing industry, as a potential non-thermal alternative to chemical and thermal methods to decontaminate foods and food contact surfaces, with minimal losses of nutrients and flavour. In PL application, the challenge consists in ensuring that all microorganisms receive the same energy dose. Thus, all factors which can have influence on the distribution and the level of energy dose within the treatment chamber as well as on the surface of solid or within liquid substrate exposed to the light treatment, are critical to the outcome of the process. This chapter aims to provide an overview of all possible parameters that may influence the effectiveness of PL treatment. The role played by the main process and design parameters, product properties and microbial factors and their interactions on the inactivation mechanism and efficacy of PL is critically analyzed and discussed. The temperature increase of the irradiated products, which is one the most limiting factors of PL for practical applications, but also the crucial role that moderate temperature coupled with PL treatment can play on the microbial inactivation are also addressed. Finally, the chapter emphasizes the need for standardizing the measurement of energy dose and experimental protocols used by the different research groups in order to allow cross comparison of different data, and suggests some engineering solutions to improve the uniformity of PL treatment.
... For the PL treatment, the bench top device SteriPulse-XL RS-3000C (Xenon Corporation, MA) was used. This system has also been applied in previous studies (Keklik et al., 2009(Keklik et al., , 2010Krishnamurthy et al., 2010;Haughton et al., 2011;Ringus and Moraru, 2013) and consisted of a sterilization time controller and a sterilization chamber, which was separated from the aircooled lamp housing by a quartz window. The lamp housing held a single, cylindrical Xenon quartz lamp. ...
As one of the emerging non-thermal technologies, pulsed light (PL) facilitates rapid, mild and residue-free microbial surface decontamination of food and food contact materials. While notable progress has been made in the characterization of the inactivation potential of PL, experimental data available on the tolerance development to the same (homologous) stress or to different (heterologous) stresses commonly applied in food manufacturing (e.g. acid, heat, salt) is rather controversial. The findings of the present study clearly indicate that both the homologous tolerance development against PL as well as the heterologous tolerance development from heat to PL can be triggered in Listeria monocytogenes. Further, conducted kinetic analysis confirmed that the conventionally applied log-linear model is not well suited to describe the inactivation of L. monocytogenes, when exposed to PL. Instead, the Weibull model as well as the log-linear + tail model were identified as suitable models. Transmission Electron Microscopic (TEM) approaches allow suggestions on the morphological alterations in L. monocytogenes cells after being subjected to PL.
... The shadow effect will then generate a tail in the inactivation curve because part of the microbial population will never be reached by light. In solids, microorganisms can be shielded by surface features such as the achnes of strawberries or the druplets of raspberries (Bialka et al., 2008) or by surface irregularities of food contact surfaces (Ringus & Moraru, 2013). In liquids, turbidity and suspended solids area main obstacles for microbial inactivation although appropriate mixing can maximize the exposure to light of all microorganisms present in the liquid mass (G omez-L opez, Koutchma, & Linden, 2012). ...
The purpose of this timely review is to critically appraise and to assess the potential significance of best-published microbial inactivation kinetic data generated by pulsed light (PL). The importance of selecting different inactivation models to describe the PL inactivation kinetics is highlighted. Current methods for the detection of viable-but-nonculturable (VBNC) organisms post PL-treatments are outlined along with the limitations of these methods within food microbiology. Greater emphasis should be placed on elucidating appropriate inactivation kinetic model(s) to cater for the occurrence of these VBNC organisms that are underestimated in number using traditional culture-based enumeration methods. Finally, the importance of further molecular and combinational research to tackle the potential threat posed by VBNC organisms with regard to kinetic inactivation modelling and nexus to public health and food safety is presented.
... Three microorganism models were chosen according to a risk analysis of agri-food companies that use wooden packaging. The bacterial pathogen Listeria monocytogenes was chosen as a known risk for dairies (Midelet and Carpentier 2002;Carrascosa et al. 2012;Awang Salleh et al. 2003), which may also be responsible for cross-contamination of products because of its great survival on working surfaces (Kang et al. 2007;Cox et al. 1989;Ringus and Moraru 2013). A reference strain of Escherichia coli was chosen to investigate the behavior of a gram-negative bacterium on wooden surfaces (Dore and Lees 1995;Pangloli et al. 2009;Taylor et al. 2013). ...
As direct food contact material, wood is subject to the European regulation n° 1935/2004 of the 27th of October 2004 which specifies that materials intended for safe food contact must not interfere with foodstuffs characteristics. In order to comply with this regulation, it’s important to provide an efficient recovery method allowing the determination of the microbial load on the wooden surfaces in direct contact with products. This study compared three recovery methods of microorganisms. This study compares three methods of recovering microorganisms from wood surfaces. We chose three microorganisms models well-known as risk in food-industry: Escherichia coli (the vegetable sector), Listeria monocytogenes (the dairy sector) and Penicillium expansum (the fruit sector), at various concentrations. Tests were realized on three types of wooden surfaces, either dry or wet, and made of poplar, Scots pine and spruce, which are commonly used in France for wood packaging in food-industry. We identified which factors influenced micro-organisms recovery rates: wood humidity, contact times and wood species. The most reliable recovery method will be use as a basis for the development of specific standard for the assessment of the food safety of wood packaging.
... Pulsed-light technology has been found effective for eliminating bacteria and fungi on eggshells (28), on fruits (29), in fruit juices (30,31), on packaged chicken (32), and on food packaging materials (33). The FDA has recommended a total fluence up to 12 J Arrows: 1, intact particle; 2, apparently intact particles; 3, distorted particle; 4, debris; 5, empty particle. ...
Pulsed light is a non-thermal processing technology recognized by the FDA for killing microorganisms on food surfaces, with cumulative fluences up to 12 J cm(-2). In this study, we investigated its efficacy for inactivating murine norovirus 1 (MNV-1) as human norovirus surrogate in PBS buffer, hard water, mineral water, turbid water and sewage treatment effluent and on food-contact surfaces including high-density polyethylene, polyvinyl chloride and stainless steel, free or in an alginate matrix. The pulsed light device emitted a broadband spectrum (200-1000 nm) at a fluence of 0.67 J cm(-2) per pulse with 2 % UV at 8 cm beneath the lamp. Reductions in viral infectivity exceeded 3 log10 in less than 3 seconds (5 pulses, 3.45 J cm(-2)) in clear suspensions and on clean surfaces even in the presence of alginate, and in 6 seconds (11 pulses, 7.60 J cm(-2)) on fouled surfaces except for stainless steel (2.6 log10). The presence of protein or bentonite interfered with viral inactivation. Analysis of the morphology, the viral proteins and the RNA integrity of the treated MNV-1 allowed us to elucidate the mechanisms involved in the antiviral activity of pulsed light. Pulsed light appeared to disrupt MNV-1 structure and degrade viral protein and RNA. The results suggest that pulsed light technology could provide effective alternative means of inactivating noroviruses in wastewaters, in clear beverages, in drinking water or food-handling surfaces in the presence or absence of biofilms.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
... Another type of UV radiation source used for decontamination is the pulsed UV lamp (PUV), which produces a broad radiation spectrum (100-1000 nm) by pulsing the discharge produced by xenon lamps (1). A great number of studies have shown high efficiency of these pulsed UV radiation systems for inactivation of vegetative bacteria (3)(4)(5)(6), endospores (3,7), yeasts (3,8,9) and molds (7,10,11). A more recent study by Schaefer et al. (12) described a different type of pulsed UV radiation systemsurface discharge (SD) lampused for water treatment. ...
Among different physical and chemical agents, the UV radiation appears to be an important route for inactivation of resistant microorganisms. The present study introduces a new mercury free Dielectric Barrier Discharge (DBD) flat lamp, where the biocide action comes from the UV emission produced by rare earth phosphor obtained by spray pyrolysis, following plasma excitation. In this study, the emission intensity of the prototype lamp is tuned by controlling gas pressure and electrical power, 500 mbar and 15 W, corresponding to optimal conditions. In order to characterize the prototype lamp, the energetic output, temperature increase following lamp ignition and ozone production of the source were measured. The bactericidal experiments carried out showed excellent results for several gram-positive and gram-negative bacterial strains, thus demonstrating the high decontamination efficiency of the DBD flat lamp. Finally, the study of the external morphology of the microorganisms after the exposure to the UV emission suggested that other mechanisms than the bacterial DNA damage could be involved in the inactivation process.This article is protected by copyright. All rights reserved.
... It is widely used to explain the inactivation of microorganisms using different treatments e.g. PEF [30,31] or PL [32][33][34] or simply the survival of microorganisms on different substrates [35]. ...
Experimental tests were performed to evaluate the effect of intense pulsed light (IPL) treatment on
microbial inactivation of yeast cell suspensions of Saccharomyces cerevisiae CBS 493.94 and Candida
utilis MIUG 3.5. Regression analysis of microbial inactivation with IPL was then investigated. The aim of
this study was to apply the response surface methodology (RSM) to define the relationship between the
reduction of yeast cells and the process parameters, namely energetic density of light and duration of IPL
treatment. Moreover, RSM was used to verify the predicted models and to adapt them on particular
conditions of yeast cells inactivation by IPL treatment. The final model shows the dependency of the
yeast cells reduction by independent variables (energetic density of light and duration of IPL treatment)
and certain binary interactions of the IPL process parameters. The response surface follows the reduction
of yeast cells and reaches the lowest level for N/No = 0. This level represents the optimal area of the
response surface, which is ideal for any microbial inactivation treatment.
... Another type of UV radiation source used for decontamination is the pulsed UV lamp (PUV), which produces a broad radiation spectrum (100-1000 nm) by pulsing the discharge produced by xenon lamps (1). A great number of studies have shown high efficiency of these pulsed UV radiation systems for inactivation of vegetative bacteria (3)(4)(5)(6), endospores (3,7), yeasts (3,8,9) and molds (7,10,11). A more recent study by Schaefer et al. (12) described a different type of pulsed UV radiation systemsurface discharge (SD) lampused for water treatment. ...
In this paper, we investigate the UVC light emission from phosphors under plasma excitation for anti-microbial testing on Escherichia coli (E-coli).
Pulsed light (PL) is an emerging processing method that utilizes short duration, high intense pulses of polychromatic light to disinfect food, food contact surfaces and packaging materials, through photochemical, photothermal, and photophysical mechanisms. Moreover, PL can be used to enhance functionality and reduce allergenic power of food and food ingredients. These effects are predominately derived from the UV portion of the PL spectrum. However, although the first industrial commercial applications have been achieved, the technique possess some intrinsic limitations, which make it suitable especially for smooth surface and transparent drinks, that have impeded till now the widespread exploitation in food industry. In this chapter, the fundamentals principle of PL technology, the mechanism of action, as well as the role played by the main process and design parameters, product properties and microbial factors and their interactions on the inactivation mechanism and efficacy of PL is critically analyzed and discussed. The most critical aspects of PL equipment and the different technological solution that could be adopted to improve the efficiency of PL treatment are also presented. The chapter then describe the applications of PL in food sector, emphasizing the main advantages and shortcomings in terms of their impact on the safety, nutritional, and health properties of food products. Moreover, the general discussion also covers the analysis of the energy consumption and sustainability aspects associate to PL technology, and conclude with the recent advancements and future perspectives.
In this study, electron beam (EB) irradiation was used for the inactivation of Bacillus atrophaeus on the surface of polythylene terephthalate (PET) bottle preform and high-density polyethylene (HDPE) bottle caps. The effects of EB irradiation doses (0,1,3,5,7,9 kGy) and original inoculated colony counts (10¹,10²,10³,10⁴,10⁵,10⁶,10⁷ CFU/sample) were evaluated on the residues of B. atrophaeus and the quality attributes of bottle caps and preform. A Weibull model for simulating the sterilization data was established by fitting the microorganism inactivation curves with a high coefficient (R² > 0.93). The reductions of the microorganism lethal rate (log N/N0) up to 7.11log, 6.21log, 5.59log were shown on 38mm bottle cap, 28mm bottle cap and bottle preform with the original colony counts of 10⁷ CFU/sample after the EB irradiation treatment at 9kGy, respectively. The b* values of bottle preform and caps were slightly affected and the highest color change was observed for 28mm bottle cap treated by 9kGy EB irradiation, which resulted in a decrease of b* value from −39.86 ± 0.15 to −41.25 ± 0.42. Nevertheless, EB irradiation could be applied in the decontamination of PET bottle preform and HDPE bottle caps under reasonable doses.
Non‐thermal food processing technologies have receiveda lot of attention in recent years as an alternative to conventional heat treatments. The pulsed light treatment (PL) is mostly applied to pre‐packaged foods in order to avoid post‐process contamination. However, for PL to fulfill its purpose regarding packaged foods, the packaging must comply with a series of requisites that may result in safer and better‐quality foods. This review focuses on packaging material requisites for packaging PL‐treated foods. In addition, the influence of PL on the properties of the materials are addressed. Furthermore, aspects regarding decontamination of packages and foods as well as their quality are described.The PL treatment has shown a positive effect on decontamination of packaging, products derived from fruits and vegetables, meat products, dairy products, fish and seafood. In addition, PL often leads to the extension of the food shelf life.
50-day free download https://authors.elsevier.com/c/1bKSy16Ds1liJw
The outbreaks of Cronobacter sakazakii, Salmonella spp, and Bacillus cereus in powdered foods have been increasing in worldwide. However, an effective method to pasteurize powdered foods before consumption remains lacking. A prototype Intense Pulsed Light (IPL) system was developed to disinfect powdered foods under different IPL and environmental conditions. Synergistic effect of IPL and TiO2 photocatalysis on microbial inactivation was studied. The results show that high energy intensity of each pulse, high peak intensity, and short pulsed duration contributed to a high microbe inactivation. With TiO2 photocatalysis, one additional log10 reduction was achieved, bringing the total log reduction to 4.71±0.07 (C. sakazakii), 3.49±0.01 (E. faecium), and 2.52±0.10 (B. cereus) in non-fat dry milk, and 5.42±0.10 (C. sakazakii), 4.95±0.24 (E. faecium), 2.80±0.23 (B. cereus) in wheat flour. IPL treatment combined with the TiO2 photocatalysis exhibits a strong potential to reduce the energy consumption in improving the safety of powdered foods.
Aseptic processing and packaging are a method of preservation in which a liquid food (or pharmaceutical) product is commercially sterilized, typically by heating and holding at an elevated temperature followed by cooling, then filled into a sterilized package and hermetically sealed with a sterilized closure in a commercially sterile environment. Products manufactured using aseptic technology typically result in better quality due to the short processing times as compared to other shelf stable products produced using traditional technologies such as canning, which also drastically limits package sizes and configurations. Because aseptic products can be packaging in a wide variety of package types and sizes it is widely appealing to consumers and offers great flexibility to processors. Aseptic processing has seen steady growth and is poised to see continued growth in new food categories as the demand for convenient, clean label food increases. Though industry has been slow to apply aseptic processing to multiphase or non-homogenous foods, consumer demand for minimally processed, nutritious foods of high quality will lead to many more multiphase and particle foods being processed aseptically in the future.
Pulsed light (PL) inactivation kinetics of Escherichia coli K-12, Clostridium sporogenes and Geobacillus stearothermophilus were evaluated under different treatment conditions. The PL system was factory set to operate at three pulses per second with a pulse width of 360 microseconds exposing samples placed on one of the 9 trays on a rack. Two PL parameters were evaluated in the study: number of pulses (a time factor) and the tray position (a spatial distance factor) both influencing the amount of light energy absorbed. As expected, the level of microbial inactivation increased with an increase in the number of pulses (from 1 to 15) and decreased with an increase in the special distance (Tray # 1 to 9) away from the light source. Both the number of pulses and spatial distance as well as their interactions were found to have a significant effect (P<0.05) on the extent of microbial inactivation. Vegetative cells of E. coli were most sensitive to PL treatment with a maximum 5 logarithmic reductions on Tray 1 after a 12-pulse treatment (4 s). G. stearothermophilus was more resistant to PL than C. sporogenes. Overall, the PL treatments (12-15 pulses) achieved a minimum four logarithmic reductions in the populations of all three microorganisms on the top tray at doses still below 12 J/cm², the FDA-approved limit.
The main goal of this study was to evaluate the effectiveness of a combination of antimicrobial films and Pulsed Light (PL) on inactivation of Listeria innocua on Cheddar cheese surface, and maintaining of product quality during refrigerated storage. The properties of antimicrobial starch films (ASF) containing sodium benzoate (ASF-SB), citric acid (ASF-CA), and both (ASF-CASB), prepared by casting and irradiated with PL, were evaluated. These films were used as packaging for Cheddar cheese slices that were surface inoculated with L. innocua at an initial inoculum level of 7 log CFU per cheese slice. PL had no effects on the structure of ASF. PL applied in combination with ASF-CA achieved an average of 4.5 log CFU reduction of L. innocua after 3 days of storage at 4 °C. However, significant changes in physicochemical properties of cheese, including pH, moisture level and mechanical properties, were observed after 7 days of refrigerated storage. These results suggest that, while PL-ASF can be effective in reducing L. innocua on Cheddar cheese surface, this combination treatment may induce some quality changes in the product.
UVC LED lamps have gained interest as a possible technology to replace the use of low– pressure mercury UV lamps due to the Minamata convention which is an international treaty enacted to eliminate the use of mercury. In this study, we investigated the influence of surface properties on inactivation efficacy of foodborne pathogens (E. coli O157:H7, S. Typhimurium, and L. monocytogenes) on various food contact surfaces, including glass, PVC, Stainless steel (SUS), Teflon, and silicon by using UVC light-emitting-diode (LED) irradiation. An optimized treatment chamber was constructed and UVC LED irradiation was applied to spot-inoculated surfaces. Also, in order to achieve enhanced pathogen inactivation, combined intervention of 60 °C mild heat and UVC LED irradiation was applied. Different levels of inactivation of foodborne pathogens were observed among surfaces; bactericidal effect decreased in this order: glass, PVC, SUS, Teflon, and silicon (0.5–1 log reduction differences), and this order was closely associated with surface hydrophobicity and roughness. Because of varying hydrophobicity among different surfaces, different bacterial stacking arrangements were developed, and causing undesirable shading effects negating collimated UVC LED irradiation of pathogens located beneath the top layer. Combination treatment of 60 °C mild heat and UVC LED achieved an additive or synergistic inactivation effect (up to 1 log reduction) on E. coli O157:H7, S. Typhimurium, and L. monocytogenes. The combined treatment can compensate for lower penetration and other limitations of UV irradiation, so that effective control of bacteria on food processing surfaces can occur.
The objective of this study was to measure the inactivation efficiencies of intense pulsed light (IPL) on six types of bacteria and determine how the efficiency values are related to the spectral transmittance of IPL. All of the microorganisms exhibited up to 7-log CFU/mL reductions, and the double-Weibull survival model provided the best fit to the inactivation curves. We obtained 4Dv values (which is the fluence required to inactivate 99.99% of viable cells) and zv values (which is the increase in lamp voltage required for a 1-log reduction of the 4Dv value) for lamp voltages ranging from 800 to 1800 V (corresponding to total fluences from 0.00 to 11.41 J/cm²). The 4Dv values for Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Enteritidis, and Shigella sonnei for IPL treatment at 1800 V were 1.57, 0.66, 0.62, 0.79, 0.66, and 1.63 J/cm², respectively, while the corresponding zv values were 5553, 3590, 3201, 3678, 3672, and 6440 V, respectively. The variations in the sensitivity to IPL were related to differences in the transmittance of the microorganisms. A practical model was developed to predict the 4Dv values of microorganisms based on their transmittance and the IPL lamp voltage.
Traditional thermal and freezing processing techniques have been effective in maintaining a safe high quality food supply. However, increasing energy costs and the desire to purchase environmentally responsible products have been a stimulus for the development of alternative technologies. Furthermore, some products can undergo quality loss at high temperatures or freezing, which can be avoided by many alternative processing methods.
This second edition of Alternatives to Conventional Food Processing provides a review of the current major technologies that reduce energy cost and reduce environmental impact while maintaining food safety and quality. New technologies have been added and relevant legal issues have been updated. Each major technology available to the food industry is discussed by leading international experts who outline the main principles and applications of each. The degree to which they are already in commercial use and developments needed to extend their use further are addressed.
This updated reference will be of interest to academic and industrial scientists and engineers across disciplines in the global food industry and in research, and to those needing information in greener or more sustainable technologies.
The impact of the fluence regulation on the inactivation efficiency of pulsed light (PL) surface disinfection treatments was investigated. E. coli and L. innocua were exposed to PL on a gel surface under variation of the applied voltage, the number of light flashes as well as the distance between the flash lamp and the sample surface. The results revealed deviations from the reciprocity law when the total fluence striking the sample surface was not applied at once, but subdivided into several successive light flashes. No differences were found when the fluence was delivered with only single light flashes, irrespective of the applied voltage. The pulse frequency did not have an impact on the microbial reduction within 1–5 Hz. Furthermore, the sensitivities of various bacterial strains, endospores and conidiospores were compared. Differences occurred for vegetative bacteria without a clear pattern, while bacterial endospores were more resistant. Dark pigmented mold spores were slightly more resistant than bacterial endospores. All dose-response curves exhibited a downward concavity, except for P. aeruginosa.
Industrial relevance
This study shows that the inactivation of bacteria on e.g. food surfaces by pulsed light systems depends on the way of fluence dosage. While it is irrelevant whether the fluence is regulated by the discharge voltage or the distance between the flash lamp and the treated surface, it is more effective to apply only single light flashes of high fluence instead of several consecutive light flashes. There is furthermore no distinct trend regarding the sensitivity of bacteria to PL, variations occur on species and strain level. Bacterial spores are in general more resistant while pigmented conidiospores show a slightly higher resistance than bacterial endospores.
The objective of this study was to evaluate the influence of surface properties of produce and food contact surfaces on the antimicrobial effect of chlorine dioxide (ClO2) gas against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. The hydrophobicity of the selected surfaces was evaluated by water contact angle measurements. White light scanning interferometry (WLSI) was used to acquire surface roughness values of each surface. Produce and food contact surfaces inoculated with foodborne pathogens were treated with 20 ppmv ClO2 gas for 5, 10, and 15 min. As treatment time increased, different levels of inactivation of the three pathogens were observed among the samples. Contact angles of produce and food contact surfaces were highly and negatively correlated with the log reduction of all three pathogens. There were generally weaker correlations between the roughness values of sample surfaces and microbial reduction compared to those between hydrophobicity and microbial reduction. The results of this study showed that surface hydrophobicity is a more important factor relative to bacterial inactivation by ClO2 gas from the surface than is surface roughness. Also, the existence of crevices with features of similar size to the pathogen cell was more important than the Ra and Rq values in the inactivation of pathogens.
Tra le numerose funzioni assegnate ai materiali e ai sistemi di confezionamento, le più importanti sono certamente quelle relative alla protezione degli alimenti e alla prevenzione delle possibili alterazioni di natura microbica, i cui effetti possono essere deleted sia per la qualità sia per la sicurezza dei prodotti. Una conoscenza corretta e approfondita di questo fondamentale ruolo del packaging — e, soprattutto, la possibilità di poterlo stimare e quantificare in anticipo — è particolarmente utile nella scelta delle forme di confezionamento più idonee e nell’organizzazione e nella gestione della logistica distributiva.
High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 mu g per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected.
In this paper, we systematically address the performance of cellulose nanocrystals (CNs) coated flexible food packaging films. Firstly, the morphology of CNs from cotton linters and homogeneity of its coating on different substrates were characterized by transmission electronic microscopy and atomic force microscopy. Then, the 1.5 mu m thick CNs coating on polyethylene terephthalate (PET), oriented polypropylene, oriented polyamide (OPA), and cellophane films were characterized for their mechanical, optical, anti-fog, and barrier properties. CNs coating reduces the coefficient of friction while maintaining high transparency (similar to 90 %) and low haze (3-4 %) values, and shows excellent anti-fog properties and remarkable oxygen barrier (oxygen permeability coefficient of CNs coating, P'O-2, 0.003 cm(3) mu m m(-2) 24 h(-1) kPa(-1)). In addition, the Gelbo flex test combined with oxygen permeance (PO2) measurements and optical microscopy are firstly reported for evaluating the durability of coatings, revealing that the CNs coated PET and OPA provide the best performance among the investigated coated films. CNs are therefore considered to be a promising multi-functional coating for flexible food packaging.
A treatment combining hydrogen peroxide and ultra-violet (UV-C) irradiation was assessed for reduction of microbial contamination in pre-formed food packaging cartons. There was a synergistic effect between low concentrations (0 – 5% wt/vol) of hydrogen peroxide and UV-C irradiation (10 s) on spores of Bacillus subtilis, the maximum lethality occurring between 0.5 and 1% peroxide. A combined treatment using 1% hydrogen peroxide and 10 s of UV-C irradiation was also effective against a variety of other organisms (spores and vegetative cells). The efficiency of the treatment was dependent on the type of inner surface of the carton. A greater lethal effect was obtained against B. subtilis spores in polyethylene-lined cartons than in aluminium/polyethylene laminate-lined cartons (5.1 and 3.5 decimal reductions in numbers respectively, using a combined treatment with 1% peroxide and 10 s of UV-C).
Reflectivity, smoothness and geometry of several types of food packaging board were studied in relation to the effectiveness of decontamination treatments involving ultraviolet (UV-C, 254 nm) irradiation. Surfaces containing aluminum in the laminate reflected more light in the 325 to 550 nm range and showed a lower lethal effect when Bacillus subtilis spores were irradiated. Visible light of wavelengths between 325 and 550 nm is known to cause photoreactivation of UV damage in vegetative cells. It was suggested that a similar phenomenon might occur in spores on reflective surfaces. Smoothness of the board surface was not an important factor in the extent or the variability of the lethal effect. The geometry of the irradiated surface was shown to be important for aluminum/polyethylene laminatelined surfaces only, as more spores were killed on board normal to incident UV-C irradiation than in cartons with reflective angles. Spores on the inner sides of this type of carton may have received more reflected li...
Pulsed light (PL) treatment has been proven effective for killing a wide variety of microorganisms on foods and food contact materials. However, there is concern regarding how shading may impact the effectiveness of PL when applied to imperfect surfaces. The main objective of this work was to examine how surface properties, particularly topography, influence the microbicidal effect of PL. Four types of stainless-steel surfaces were inoculated with Listeria innocua and treated with up to 12 pulses of light. The highest level of inactivation achieved was about a 4-log reduction. Initially, an increase in inactivation with increasing treatment intensity was observed, but the inactivation curves tailed off above 3 light pulses. The differences in inactivation levels among the 4 finishes at specific treatment levels were rather insignificant, but some interesting trends were observed. At low treatment levels, inactivation on the smoothest finish was slightly lower than for the other surfaces, due to clustering of the cells on the highly hydrophobic smooth surface and to its reflective nature. For the roughest surface, scanning electron microscopy (SEM) imaging confirmed the preferential location of the cells inside surface features, which also promoted a relatively uniform distribution of the cells across the surface. This counter balanced to some extent of the shading effects, and as a result inactivation on the roughest surface was comparable to inactivation on the smoother surfaces. These results demonstrate that PL can be effective on both smooth and rough surfaces, but also indicate a complex effect of various surface properties on inactivation.
The efficacy of high-intensity light pulse (HILP) technology (3 Hz, maximum of 505 J/pulse, and a pulse duration of 360 μs) for the decontamination of raw chicken and associated packaging and surface materials was investigated. Its ability to reduce microbial counts on raw chicken through plastic films was also examined. Complete inactivation of Campylobacter spp., Escherichia coli, and Salmonella Enteritidis in liquid was achieved after 30 sec HILP treatment. Reductions of 3.56, 4.69, and 4.60 log₁₀ cfu/cm²) were observed after 5 sec HILP treatment of Campylobacter jejuni, E. coli, and Salmonella Enteritidis inoculated onto packaging materials and contact surfaces, respectively. The greatest reductions on inoculated chicken skin were 1.22, 1.69, and 1.27 log₁₀ cfu/g for C. jejuni, E. coli, and Salmonella Enteritidis, respectively. Corresponding reductions on inoculated skinless breast meat were 0.96, 1.13, and 1.35 log₁₀ cfu/g. The effectiveness of HILP treatment for reducing microbial levels on chicken increased as the film thickness decreased. HILP treatments of 2 sec did not significantly affect the color of raw chicken although treatments of 30 sec impacted color. This study has shown HILP to be an effective method for the decontamination of packaging and surface materials. Additionally, it has demonstrated the potential of HILP to be used as a decontamination method for packaged chicken.
The effectiveness of pulsed UV light on the microbial load of boneless chicken breast was investigated. Unpackaged and vacuum-packaged samples inoculated with an antibiotic-resistant strain of Salmonella Typhimurium on the top surfaces were treated with pulsed UV light for 5, 15, 30, 45, and 60 s at 5, 8, and 13 cm distance from the quartz window in the pulsed UV light chamber. The log(10) reductions of Salmonella (cfu/cm(2)) on unpackaged samples varied from 1.2 to 2.4 after a 5-s treatment at 13 cm and a 60-s treatment at 5 cm, respectively. The log(10) reductions on vacuum-packaged samples varied from 0.8 to 2.4 after the 5-s treatment at 13 cm and the 60-s treatment at 5 cm, respectively. The optimum treatment conditions were determined to be 5 cm-15 s for unpackaged samples and 5 cm-30 s for vacuum-packaged samples, both of which resulted in about 2 log(10) reduction (approximately 99%). The total energy and temperatures of samples increased with longer treatment time and shorter distance from the quartz window in the pulsed UV light chamber. The changes in chemical quality and color of samples were determined after mild (at 13 cm for 5 s), moderate (at 8 cm for 30 s), and extreme (at 5 cm for 60 s) treatments. Neither malonaldehyde contents nor color parameters changed significantly (P > 0.05) after mild and moderate treatments. Mechanical properties of the packaging material were analyzed before and after pulsed UV light treatments. The elastic modulus at both along-machine and perpendicular-to-machine direction and yield strength at perpendicular-to-machine direction changed significantly (P < 0.05) after extreme treatment. Overall, these results clearly indicate that pulsed UV light has a potential to be used for decontamination of unpackaged and vacuum-packaged poultry.
The risk of listeriosis associated with ready-to-eat foods is a major concern in the United States. Pulsed light (PL) treatment has been effective for killing Listeria. The possibility of enhancing the antilisterial capability of PL treatment by combining PL with an additional hurdle, the natural antimicrobial nisin, was explored in this study. First, the ability of Listeria innocua to mimic the response of Listeria monocytogenes to PL treatment was demonstrated. Subsequently, a series of inoculation studies was performed in which canned sausages were surface inoculated with L. innocua as a surrogate for L. monocytogenes and then treated with a commercial preparation of nisin (Nisaplin), PL, or a combination of the two treatments. The application of a Nisaplin dip alone resulted in an immediate reduction of L. innocua by 2.35 +/- 0.09 log CFU. PL reduced L. innocua by 1.37 +/- 0.30 log CFU after exposure to 9.4 J/cm2. A total reduction of 4.03 +/- 0.15 log CFU was recorded after the combined treatment of Nisaplin and PL for 48 h at 4 degrees C. The long-term survival of L. innocua was evaluated on sausages stored at 4 degrees C. Treatment with Nisaplin and PL resulted in a 4- to 5-log reduction for two replicate studies. The combination treatment resulted in no significant microbial growth during 28 and 48 days of refrigerated storage in the first and second replicates, respectively. These results suggest that this combination treatment can be used as an effective antilisterial step in the production of ready-to-eat foods.
This study investigated the physicochemical forces involving the adhesion of Listeria monocytogenes to surfaces. A total of 22 strains of L. monocytogenes were compared for relative surface hydrophobicity with the salt aggregation test. Cell surface charges and hydrophobicity of L. monocytogenes Scott A were also determined by electrophoretic mobility, hydrophobic-interaction chromatography, and contact angle measurements. Electrokinetic measurements indicated that the strain Scott A has a negative electrophoretic mobility. Physicochemical characterization of L. monocytogenes by various methods indicates that this microorganism is hydrophilic. All L. monocytogenes strains tested with the salt aggregation test method aggregated a at very high ammonium sulfate molarities. The hydrophobicity-interaction chromatography results show that L. monocytogenes Scott A cells do not adhere to octyl-Sepharose unless the pH is low. Results from contact angle measurements showed that the surface free energy of strain Scott A was 65.9 mJ.m-2, classifying this microorganism as a hydrophilic bacterium. In addition, the interfacial free energy of adhesion of L. monocytogenes Scott A estimated for polypropylene and rubber was lower than that for glass and stainless steel. However, these theoretical implications could not be correlated with the attachment capabilities of L. monocytogenes.
Pulsed light (PL) treatment is an alternative to traditional thermal treatment that has the potential to achieve several log-cycle reductions in the concentration of microorganisms. One issue that is still debated is related to what specifically causes cell death after PL treatments. The main objective of this work was to elucidate which portions of the PL range are responsible for bacterial inactivation. Stainless steel coupons with controlled surface properties were inoculated with a known concentration of Listeria innocua in the stationary growth phase and treated with 1 to 12 pulses of light at a pulse rate of 3 pulses per s and a pulse width of 360 micros. The effects of the full spectrum (lambda = 180 to 1,100 nm) were compared with the effects obtained when only certain regions of UV, visible, and near-infrared light were used. The effectiveness of the treatments was determined in parallel by the standard plate count and most-probable-number techniques. At a fluence of about 6 J/cm(2), the full-spectrum PL treatment resulted in a 4.08-log reduction of L. innocua on a Mill finish surface, the removal of lambda < 200 nm diminished the reduction to only 1.64 log, and total elimination of UV light resulted in no lethal effects on L. innocua. Overwhelmingly, the portions of the PL spectrum responsible for bacterial death are the UV-B and UV-C spectral ranges (X < 300 nm), with some death taking place during exposure to UV-A radiation (300 < lambda < 400 nm) and no observable death upon exposure to visible and near-infrared light (lambda > 400 nm). This work provides additional supporting evidence that cell death in PL treatment is due to exposure to UV light. Additionally, it was shown that even a minor modification of the light path or the UV light spectrum in PL treatments can have a significant negative impact on the treatment intensity and effectiveness.
Pulsed light (PL) treatment can effectively reduce microbial populations in clear substrates and on surfaces, but its effectiveness varies as a function of substrate or treatment-related factors. For PL to be successfully adopted by the food industry, all factors of influence, as well as the inactivation kinetics for the microorganisms of concern, must be elucidated. In this study, the inactivation kinetics of Listeria innocua and the effect of inoculum size on PL inactivation were investigated. Stainless steel coupons (50.8 by 101.6 mm) of defined surface properties and transparent glass chamber slides (25.4 by 50.8 by 10 mm) were each inoculated with 1 ml of aqueous suspensions of L. innocua containing inoculum populations of up to 10(9) CFU. The thickness of the liquid layer in the glass slides was 1.16 mm. The inoculated substrates were exposed to PL treatment of up to 17 J/cm2 in a static PL chamber equipped with a pulsed Xenon lamp. Survivors were recovered and enumerated by both standard plate counting and most-probable-number procedures. The data indicated that in clear liquids, PL resulted in more than a 6-log reduction of L. innocua after a 12-J/cm2 treatment, regardless of the initial inoculum size. For the stainless steel surfaces, less than a 4-log reduction after a 12-J/cm2 treatment and a noticeable effect of substrate characteristics and inoculum size on inactivation were observed. The survivor curves showed pronounced tailing for all substrates used in the study. The Weibull model accurately predicted the survivor ratios for the PL treatment of L. innocua in clear liquids, with a shape and scale parameter of 0.33 and 3.01, respectively. The Weibull model resulted in significant overestimation of PL effectiveness for the stainless steel substrates, where the influence of various substrate properties and inoculum level on inactivation was significant.
This article deals with evolution of packed foodstuff quality with time of storage. The transport of small volatile molecules (flavor compounds, water vapor, and gases) into and through flexible food packaging materials is reviewed, as well as their multiple transfers. Sorption, diffusion, and permeation phenomena are distinguished. Transport properties are largely determined by packaging characteristics, flavor molecules properties, food matrix composition, and environmental conditions. Transfer of small volatile molecules into and through food packaging materials can modify food quality and properties of the packaging materials, thus possibly altering packed foodstuff shelflife. More research is required on transport of flavor molecules through packaging materials by considering liquid and solid food matrices flavored with mixtures of aroma compounds at more realistic concentrations; interactions of aroma compounds with food matrices, and with packaging being followed during storage in given environmental conditions.
In aseptic packaging systems, packaging materials are sterilized by various methods in order to kill microorganisms contained in the packages during forming and transport through the machine prior to filling. Experimental data as well as theoretical results from several years of research in the area of sterilization methods for effective inactivation of microorganisms on surfaces of aseptic packaging materials are compiled and presented in order to choose the right method of sterilization by the food processing industry for a successful operation. Hydrogen peroxide, with concentrations up to 30%, temperatures of up to 80°C and contact times up to 15 s, with or without wetting agent, has been found to be successful for inline aseptic packaging. The final product must not contain greater than 0.5 ppm H2O2. Economic considerations and non-uniform dose delivery to pre-formed containers inhibit commercial adoption of ionizing radiation sterilization in-line with aseptic packaging systems.
Intense light pulse (ILP) is one of the emerging non-thermal techniques investigated as an alternative to traditional thermal treatment because it has been proven to be effective for microbial inactivation on food surfaces and food packages. The aim of this study was to evaluate the possibility of using pulsed light treatment for the effective killing of moulds on paper–polyethylene packaging material. Coupons of 20 × 20 mm paper–polyethylene were artificially contaminated with Cladosporium herbarum, Aspergillus niger, Aspergillus repens and Aspergillus cinnamomeus than subjected to different light energetic densities (from 0.244 to 0.977 J/cm2) for different durations (from 10 × 10-3 to 30 × 10-3 s). The results showed that there is a significant reduction of population along with an increase of light fluence and ILP treatment duration. The highest level of inactivation achieved in this study was about a 2.7-log reduction, which is more than
enough for a normal contaminated packaging material. It is estimated that pulse light treatment could lead to an effective reduction of moulds, being also possible to obtain a sterile surface of the packaging material. Blastospores as those produced by C. herbarum are easier destroyed (z = 0.795 J/cm2) than fialospores as those produced by aspergilli (z = 0.81–0.927 J/cm2). Spore colour seems to play some role in spore resistance to light pulses: green fialospores, as those produced by A. repens, has higher z values (0.927 J/cm2) than the black or brown ones as those produced by A. niger (z = 0.81 J/cm2), and A. cinnamomeus (z = 0.875 J/cm2) respectively.
Measurements were made of dynamic mechanical response spectra and stress–strain properties at room temperature on films of isotactic polypropylene and low-density polyethylene prior and after ultraviolet irradiation in a Xenotest 450 apparatus. The period of irradiation that caused a deep deterioration of ultimate mechanical properties influenced the dynamic mechanical properties only insignificantly. This is attributed to the heterogeneous nature of the photo-oxidative degradation process which is concentrated in a finite number of sites, thus forming crack precursors rather than changing the material properties in bulk. For a biaxially oriented tubular film of low-density polyethylene, anisotropic embrittlement after exposure in Xenotest 450 was observed. This even reversed the order of strain-at-break values in the two main directions of the film. This is remarkably similar to the effect of artificial incisions introduced into the specimens.
Ultraviolet (u.v.) laser irradiation has been used to inactivate Bacillus subtilis spores deposited on to planar aluminium- and polyethylene-coated packaging surfaces. Kill kinetics were found to be diphasic, with an initial rapid inactivation phase followed by tailing. Although no definitive evidence was obtained, it is thought that spores located within packaging crevices/pores were primarily responsible for the observed tailing. Surviving spores were also found on the unexposed underside of cards and, to a lesser extent, within clumps. The log count reduction in B. subtilis was dependent on spore loading and total u.v. dose. In comparison, packaging surface composition, fluence (2–18 Jm−2) and frequency (40–150 Hz) had only a negligible effect. By irradiating boards carrying 106 spores, with a dose of 11·5 J cm−2, a log count reduction >5 was obtained. The mode of spore inactivation was primarily through DNA disruption. This was confirmed by the high sensitivity of spores lacking protective, small, acid-soluble proteins, in addition to the high frequency of auxotrophic and asporogenous mutations found amongst survivors.
Microbial contamination of food-contact surfaces is an ongoing concern for the food industry. Under favorable conditions, bacterial cells can adhere and reproduce. Such microorganisms, if not completely removed, can contribute to the formation of biofilms that will compromise the quality and safety of foods. By understanding the relationship between surface conditions and microbial adhesion, strategies can be developed that when realized would greatly inhibit, if not prevent, the attachment of bacteria and spores.
The effectiveness of pulsed UV-light on the microbial load and quality of unpackaged and vacuum-packaged chicken frankfurters was investigated. Samples were inoculated with Listeria monocytogenes Scott A on the top surfaces, and then treated with pulsed UV-light for 5, 15, 30, 45, and 60 s at 5, 8, and 13 cm distance from the quartz window in a pulsed UV-light chamber. Log reductions (CFU/cm(2)) on unpackaged samples were between 0.3 and 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. Log reductions on packaged samples ranged from 0.1 to 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. The temperature changes of samples and total energy (J/cm(2)) received at each treatment condition were monitored. The extent of lipid peroxidation and the color were determined by thiobarbituric acid-reactive substances (TBARS) test and CIELAB color method, respectively. Lipid peroxidation of samples did not change significantly (P > 0.05) after mild (5-s treatment at 13 cm) and moderate (30-s treatment at 8 cm) treatments. Significant differences (P < 0.05) in color parameters were observed after treatments of both unpackaged and packaged samples. Packaging material was also analyzed for mechanical properties. The elastic modulus, yield strength, percent elongation at yield point, maximum tensile strength, and percent elongation at break did not change significantly (P > 0.05) after mild treatment. Overall, this study demonstrated that pulsed UV-light has a potential to decontaminate ready-to-eat (RTE) poultry-based food products.
A study was performed to assess the ability of pulsed light to sterilize water for injection in blow/fill/seal polyethylene containers. Pulsed light uses intense, short duration flashes of broad spectrum white light to produce high levels of microbial kill. In a first phase of testing, containers of 0.5, 5, 15, and 120 mL nominal volume were inoculated with Bacillus pumilus endospores, Bacillus subtilus variety niger strain globigii endospores, Bacillus stearothermophilus endospores, and Aspergillus niger conidiospores. Approximately 106 colony forming units of each test spore were individually inoculated into 22 replicate containers of each sample volume. Two of these containers served as inoculation recovery controls, and 10 were treated using each of two pulsed light exposure methods: single-sided treatment or treatment within a reflective cavity. Both treatments employed flashes of intense broad spectrum pulsed light delivered at one flash per second. Cavity treatment used 10 flashes to treat each container within a reflective cavity containing a single lamp. Cavity treatment yielded no recoverable survivors for any of the challenge spores from the contents of any of the 160 total samples. Single-sided treatment used 20 approximately 1-J/cm2 flashes from a single lamp-reflector projecting onto one side of the container Single-sided treatment yielded no recoverable survivors from the contents of the containers for any of the bacterial endospores tested, but Aspergillus niger survival was detected in 4 of the 40 single-side treated samples. A second phase of tests examined the pulsed light inactivation of Bacillus pumilus spores for a range of inoculation levels. High levels of Bacillus pumilus spore kill were obtained using only a few cavity flashes. The results show that pulsed light can provide high levels of microbial lethality and possesses potential for use as u terminal sterilization method for water for injection in filled, sealed polyethylene containers.
Ultraviolet (u.v.) laser irradiation has been used to inactivate Bacillus subtilis spores deposited on to planar aluminium- and polyethylene-coated packaging surfaces. Kill kinetics were found to be diphasic, with an initial rapid inactivation phase followed by tailing. Although no definitive evidence was obtained, it is thought that spores located within packaging crevices/pores were primarily responsible for the observed tailing. Surviving spores were also found on the unexposed underside of cards and, to a lesser extent, within clumps. The log count reduction in B. subtilis was dependent on spore loading and total u.v. dose. In comparison, packaging surface composition, fluence (2-18 Jm-2) and frequency (40-150 Hz) had only a negligible effect. By irradiating boards carrying 106 spores, with a dose of 11.5 J cm-2, a log count reduction >5 was obtained. The mode of spore inactivation was primarily through DNA disruption. This was confirmed by the high sensitivity of spores lacking protective, small, acid-soluble proteins, in addition to the high frequency of auxotrophic and asporogenous mutations found amongst survivors.
Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2. We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2-coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59 degrees +/-2 to <5 degrees. The water contact angle of the SnO2 surface was reduced only at 254 nm, while contact angle of the Si-m glass surface was not altered by light of either wavelength. Bacterial adhesion decreased by 10-50% to photocatalyzed glass surfaces. In all cases, bacteria exposed to the UV light were completely killed due to a combination of exposure to UV light and the photocatalytic activity of the glass surfaces. These results show that UV light irradiation of TiO2-coated surfaces can be an effective method of reducing bacterial adhesion.
To determine the influence of several factors on the inactivation of micro-organisms by intense light pulses (ILP).
Micro-organisms on agar media were flashed 50 times under different conditions and their inactivation measured. Micro-organisms differed in sensitivity to ILP but no pattern was observed among different groups. Several enumeration methods to quantify the effect of ILP were investigated and showed relevant differences, shading effect and photoreactivation accounted for them, the strike method yielded the most reliable results. Higher decontamination efficiencies were obtained for Petri dishes located close to the strobe and inside the illumination cone. Decontamination efficacy decreased significantly at contamination levels >6.85 log(10). After 13 successive treatments, no resistance to ILP could be demonstrated. Media warming up depended on the distance from the strobe and the number of flashes.
For an industrial implementation: the position and orientation of strobes in an unit will determine the lethality, products should be flashed as soon as possible after contamination occurs, a cooling system should be used for heat-sensitive products and flashed products should be light protected. No resistant flora is expected to develop.
Conclusions derived from this work will allow a better implementation of this decontamination technique at industrial level.
Polymer films to which bioactive compounds such as enzymes are covalently attached offer potential for in-package processing of food. Beta-galactosidase (lactase) was covalently attached to surface-functionalized low-density polyethylene films. A two-step wet chemical functionalization introduced 15.7 nmol/cm2 primary amines to the film surface. Contact angle, dye assays, X-ray photoelectron spectroscopy, and appropriate protein assays were used to characterize changes in film surface chemistry after each step in the process of attachment. Glutaraldehyde was used to covalently attach lactase to the surface at a density of 6.0 microg protein per cm2 via reductive amination. The bond between the covalently attached lactase and the functionalized polyethylene withstood heat treatment in the presence of an ionic denaturant with 74% enzyme retention, suggesting that migration of the enzyme into the food product would be unlikely. The resulting polyethylene had an enzyme activity of 0.020 lactase units (LU)/cm2 (approximately 4500 LU/g). These data suggest that enzymes that may have applications in foods can be covalently attached to inert polymer surfaces, retain significant activity, and thus have potential as a nonmigratory active packaging materials.
The experimental results on the development of a decontamination
process that uses ultraviolet light and chemical photosensitizer for
disinfecting surfaces and solutions are reported. Reduction in the
microbial viability as a function of applied UV fluence is presented for
the inactivation of Bacillus subtilis spores. Results obtained with
aqueous solutions and with surfaces indicate that pulsed UV light is
more effective than continuous UV light. Nearly three orders of
magnitude of enhanced inactivation have been achieved with the
photosensitized UV process on surfaces