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Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.

Wildlife feces can contaminate vegetables when enteric bacteria are released by rain and splashed onto crops. Regulations require growers to identify and not harvest produce that is likely contaminated, but U.S. federal standards do not define dimensions for no-harvest zones. Moreover, mulching, used to retain soil moisture and maximize crop yield may impact rain-mediated bacterial dispersal from feces. To assess dissemination from a fecal point source to lettuce grown on various mulches, lettuce cv. 'Magenta' was transplanted into raised beds with plastic, biodegradable plastic, straw, or left uncovered at field sites in Maryland and Georgia. Eleven days post-transplant, 10 g of rabbit manure spiked with ~8 log CFU g were deposited in each bed. One day following natural or simulated rain events, lettuce was sampled along 1.5 m transects on either side of fecal deposits. Lettuce-associated was semi-quantified with an MPN assay and dependence on fecal age (stale or fresh), lettuce age (baby leaf or mature head), distance from point source, mulch and post-rain days were statistically evaluated. Distance ( <0.001), fecal age ( <0.001) and mulch ( <0.01) were factors for transfer from point source to lettuce. The highest and lowest estimates were measured from lettuce grown on biodegradable plastic and straw, respectively, with a 2-log MPN difference ( <0.001). Mulch and distance were also significant factors in recovery 3 days post-rain (both <0.001), where plastic mulches differed from bare ground and straw ( <0.01). For all treatments, fewer were retrieved from lettuce at 0.3 m, 3 days post-rain compared to 1 day ( 0.001). Fitting the data to a Weibull Model predicated that a 7-log reduction in from fecal levels would be achieved at 1.2-1.4 m from the point source on plastic mulches, 0.75 m on bare soil ( <0.05) and 0.43 m on straw ( 0.01). Straw and bare ground limited rain-mediated dispersal from feces to lettuce compared to plastic mulches. Fecal age was negatively associated with dispersal. These findings can inform harvesting recommendations for measures related to animal intrusion in vegetable production areas.

Molecular characteristics of emulsifiers such as their molecular weight (MW) and surface charge, not only affect the stability of the emulsion but also can have an impact on its capacity to either inhibit or promote microbial proliferation. These characteristics can affect the behavior of pathogens such as Salmonella Typhimurium in emulsion systems. The growth and thermal resistance of S. Typhimurium were monitored at different oil content levels (20%, 40%, and 60%) in emulsions stabilized by three whey protein‐based emulsifiers: whey protein isolate (WPI), whey protein hydrolysate (WPH), and a modified WPI with an alteration of charge (WPI+). Our study revealed that emulsifier itself with different MW and surface charge had no effect on bacterial growth and inactivation without oil inclusion (p > 0.05). However, it was found that higher bacterial growth rate at 60% oil content emulsion stabilized with WPI+ (0.65 ± 0.03 log CFU/h) than WPI (0.19 ± 0.04 log CFU/h), which showed the charge of emulsifiers has different effects on microbial dynamics in oil‐in‐water emulsion. Interestingly, WPI+ in emulsions also seemed to convey protection against thermal inactivation of bacteria. These data describe a complex interrelationship between the physicochemical characteristics of the emulsifier and its interacting nature with bacterial cells. They throw even more light on the insight about the importance of a strategic approach toward emulsifier selection in food formulations. This is crucial for the food safety and stability of products. Appropriate emulsifier selection, considering molecular weight (MW) and surface charge, is instrumental in attaining desired product characteristics while controlling bacterial growth and spoilage within emulsion system. However, it is unclear whether MW or surface charge of emulsifier has any effect on bacterial growth and inactivation within emulsion. To test this, oil‐in‐water emulsions were formulated using three distinct emulsifiers: whey protein isolate (WPI), whey protein hydrolysate (WPH), and whey protein isolate under a pH lower than the isoelectric point (WPI+), with varying oil proportions (20%, 40%, and 60% [v/v]). Salmonella growth and inactivation rates were compared in these emulsions.

In previous studies, parabens in model systems enhanced the thermal inactivation of foodborne pathogens, including Cronobacter sakazakii, Salmonella enterica serotype Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. However, few studies have been conducted to evaluate this phenomenon in actual food systems. In the present study, the potential enhancement of thermal inactivation of C. sakazakii by butyl para-hydroxybenzoate (BPB) was evaluated in powdered infant formula (PIF) and nonfat dry milk (NFDM) in dry and rehydrated forms. When PIF was rehydrated with water at designated temperatures (65 to 80°C) in baby bottles, BPB did not enhance thermal inactivation. When rehydrated NFDM and lactose solutions with BPB were inoculated and heated at 58°C, BPB enhancement of thermal inactivation of C. sakazakii was negatively associated with the concentration of NFDM solutions in a dose-dependent manner, whereas thermal inactivation was enhanced in the presence of lactose regardless of its concentration, suggesting an interaction between proteins and BPB. Fluorescence testing further indicated an interaction between BPB and the proteins in PIF and NFDM. In inoculated dry NFDM with and without BPB stored at 24 and 55°C for 14 days, BPB did not substantially enhance bacterial inactivation. This study suggests that BPB is not likely to enhance mild thermal bacterial inactivation treatments in foods that have appreciable amounts of protein.

Although high-temperature heat treatments can efficiently reduce pathogen levels, they also affect the quality and nutritional profile of foods and increase the cost of processing. The food additive butyl para-hydroxybenzoate (BPB) was investigated for its potential to synergistically enhance thermal microbial inactivation at mild heating temperatures (54 to 58°C). Four foodborne pathogenic bacteria, Cronobacter sakazakii, Salmonella enterica Typhimurium, attenuated Escherichia coli O157:H7, and Listeria monocytogenes, were cultured to early stationary phase and then subjected to mild heating at 58, 55, 57, and 54°C, respectively, in a model food matrix (brain heart infusion [BHI]) containing low concentrations of BPB (≤125 ppm). The temperature used with each bacterium was selected based on the temperature that would yield an approximately 1- to 3-log reduction over 15 min of heating in BHI without BPB in a submerged coil system. The inclusion of BPB at ≤125 ppm resulted in significant enhancement of thermal inactivation, achieving 5- to >6-log reductions of the gram-negative strains with D-values of <100 s. A 3- to 4-log reduction of L. monocytogenes was achieved with a similar treatment. No significant microbial inactivation was noted in the absence of mild heating for the same time period. This study provides additional proof of concept that low-temperature inactivation of foodborne pathogens can be realized by synergistic enhancement of thermal inactivation by additives that affect microbial cell membranes.

After studies with powdered infant formula indicated that the enhancement of thermal inactivation of Cronobacter sakazakii by butyl para-hydroxybenzoate (BPB) was blocked by high protein concentrations, we hypothesized that BPB would retain its synergistic activity in foods with limited protein and lipid concentrations. This hypothesis was tested by examining the ability of BPB to enhance the thermal inactivation of C. sakazakii 607 at 58°C in commercial apple juice, including examining the effects of pH and possible synergistic effects with malic acid. Apple juice was adjusted to designated pH values of 3.2 to 9.0, supplemented with selected concentrations of BPB (≤125 ppm), inoculated with early-stationary-phase C. sakazakii 607, and thermally treated (58°C) for 15 min with a submerged coil apparatus. The same methods were used to study the enhancement of thermal inactivation by malic acid. Samples were plated on tryptic soy agar for recovery and enumeration. Survival curves were plotted, and D-values were calculated by linear regression and compared using the Tukey honestly significant difference test. BPB significantly enhanced thermal inactivation in a concentration dependent manner, with D-values of a few seconds at the original pH (3.8). The enhancement of thermal inactivation was pH dependent over the pH range of 3.4 to 9.0. Malic acid enhanced thermal inactivation; the pH was decreased from 3.8 to 3.2. These results support the hypothesis that BPB can enhance the thermal inactivation of C. sakazakii in low-protein and low-lipid foods. BPB significantly enhanced thermal inactivation of C. sakazakii in apple juice heated at 58°C.BPB and thermal treatment were synergistic over a wide pH range (3.2 to 9.0).Inactivation kinetics was influenced by BPB concentration and the presence of injured cells.Malic acid enhanced thermal inactivation over the pH range of 3.2 to 4.2.

The antimicrobial efficacy of 400 nm photoirradiated caffeic acid (CA, 5 mM) was evaluated against Escherichia coli O157:H7 and Listeria innocua. A stronger antimicrobial effect was observed on E. coli than on L. innocua where the combined treatment resulted in 4 and 1 log(CFU/mL) reductions, respectively. The treatment's effects on cellular metabolism (resazurin assay), uptake of CA (fluorescence technique) and membrane damage (propidium iodide assay) were studied in both species. CA uptake increased in both species, but membrane damage was only observed in E. coli O157:H7. The treatment had minimal impact on metabolic activity in both species. The treatment applied to the surface of spinach leaves was found to be effective against E. coli O157:H7. The novel treatment proposed in this study has the potential to improve the microbial food safety of fresh produce.

Peroxides and chlorite-based sanitizers are commonly used for washing procedures. The efficacy of these sanitizers is significantly reduced in the presence of organic content and may result in the formation of harmful secondary products. Therefore, new food-grade sanitizers with enhanced antimicrobial efficacy are needed. In this work, we tested a visible light-activated photosensitizer, Rose Bengal (RB), for the reduction of microbial load in simulated wash water. Escherichia coli BL21 and bacteriophage T7 were selected as model bacterial and viral targets, respectively. Effects of duration of illumination, growth phase of the bacterium, and the presence of organic matter on efficacy of inactivation were evaluated. Photosensitized RB was able to achieve 6 log colony-forming units (CFU)/mL reduction in the exponential-phase bacteria in the presence of high organic content (2000 ppm LB broth) within 45 min of treatment. The results also demonstrated that the stationary-phase microbes were significantly more resistant to photoinactivation as compared to the exponential-phase microbes at both low and high organic loads (200 and 2000 ppm). The results indicate that RB dye can be internalized in bacteria and induces damage to the cell membrane upon photoactivation. Viral inactivation studies demonstrated that photoactivation of RB can achieve 5 log PFU/mL reduction in viral load in the presence of 2000 ppm LB after 30 min of treatment. Overall, these results highlight the efficacy of RB as an antimicrobial against bacteria and viruses in simulated wash water and demonstrate its potential as an alternative sanitizer for the food industry.

[...]frozen food processors have fine-tuned their operations to optimize the time and temperature profiles of freezing procedures to match the quality requirements of different types of frozen foods, thereby optimizing moisture, texture, color, and flavor attributes. Distribution of frozen foods involves moving products from one cold storage warehouse to another, such as a distribution center or retail outlet. Driving Energy Efficiency: Ensuring Food Safety and Quality of Frozen Foods Cold chain monitoring and logistics significantly impact the frozen food industry's overall carbon footprint, as these are stages in the supply chain with temperature control requirements. Frozen Storage Temperature First, it is important to recognize that the typical temperature of frozen storage, transport, and distribution currently is –18 °C or 0 °F, a setpoint that is globally applied and is the result of research developed by the U.S. Department of Agriculture (USDA) in the period between 1948 and 1965.3,4,5 A series of these USDA studies ultimately defined this temperature setpoint across a variety of commodities, and over the decades, 0 °F has become the standard operating temperature across the global cold chain.

There is a growing consumer demand for safe foods that are free of additives, minimally processed, and fresh‐like in appearance and taste. While conventional thermal processing methods can address microbial safety considerations, the severity of processing invariably lowers the quality of food. To address these needs, numerous nonthermal processing methods are under investigation. In this chapter, we highlight some of these physical, nonthermal processing technologies and discuss their mechanisms of action, their benefits over conventional technologies, and their potential limitations.