Recent developments in low-moisture foods: microbial validation studies of thermal pasteurization processes.

Outbreaks associated with low-moisture foods (e.g., wheat flour, nuts, and cereals) have urged the development of novel technologies and re-validation of legacy pasteurization process. For various thermal pasteurization processes, they share same scientific facts (e.g., bacterial heat resistance increased at reduced water activity) and guidelines. However, they also face specific challenges because of their different heat transfer mechanisms, processing conditions, or associated low-moisture foods' formulations. In this article, we first introduced the general structural for validating a thermal process and the shared basic information that would support our understanding of the key elements of each thermal process. Then, we reviewed the current progress of validation studies of 7 individual heating technologies (drying roasting, radiofrequency-assisted pasteurization, superheated steam, etc.) and the combined treatments (e.g., infrared and hot air). Last, we discussed knowledge gaps that require more scientific data in the future studies. We aimed to provide a process-centric view point of thermal pasteurization studies of low-moisture foods. The information could provide detailed protocol for process developers, operators, and managers to enhance low-moisture foods safety.

Listeria monocytogenes cross-contamination during apple waxing and subsequent survival under different storage conditions.

This study evaluated Listeria monocytogenes cross-contamination between inoculated fruits, waxing brush, and uninoculated fruits during apple wax coating and investigated the fate of L. monocytogenes on wax-coated apples introduced via different wax coating schemes. There were 1.8-1.9 log10 CFU/apple reductions of L. monocytogenes on PrimaFresh 360, PrimaFresh 606, or Shield-Brite AP-450 coated apples introduced before wax coating after 6 weeks of ambient storage (22 °C and ambient relative humidity). L. monocytogenes showed a similar trend (P > 0.05) on waxed apples under cold storage (1 °C and ∼ 90% relative humidity); there were 1.8-2.0 log10 CFU/apple reductions of L. monocytogenes during the 12 weeks of cold storage regardless of wax coating type. For cross-contamination study, a waxing brush was used to wax one inoculated apple (6.2 log10 CFU/apple); then, this brush was used to wax five uninoculated apples in a sequence. There were 3.7, 3.5, 3.3, 2.9, and 2.7 log10 CFU/apple and 3.6 log10 CFU/brush of L. monocytogenes transferred from the inoculated apple to uninoculated apple 1 to apple 5, and the waxing brush, respectively. The die-off rate of L. monocytogenes on wax-coated apples contaminated during wax coating was not significantly different from that contaminated on apples before wax coating, and 1.8-1.9 log10 CFU/apple reductions were observed during the 12 weeks of cold storage. The application of wax coatings, regardless of wax coating type, did not impact the survival of endogenous yeasts and molds on apples during ambient or cold storage. L. monocytogenes transferred onto waxing brushes during wax coating remained relatively stable during the 2-week ambient holding. Fungicide application during wax coating reduced (P < 0.05) yeast and mold counts but had a minor impact (P > 0.05) on the survival of L. monocytogenes on apples after 12 weeks of cold storage. Collectively, this study indicated that a high cross-contamination risk of L. monocytogenes during apple waxing, and L. monocytogenes on wax-coated apples introduced via different scenarios is stable during subsequent cold storage, highlighting the need for potential intervention strategies to control L. monocytogenes on wax-coated apples.

High-pressure pasteurization of low-acid chilled ready-to-eat food.

The working population growth have created greater consumer demand for ready-to-eat (RTE) foods. Pasteurization is one of the most common preservation methods for commercial production of low-acid RTE cold-chain products. Proper selection of a pasteurization method plays an important role not only in ensuring microbial safety but also in maintaining food quality during storage. Better retention of flavor, color, appearance, and nutritional value of RTE products is one of the reasons for the food industry to adopt novel technologies such as high-pressure processing (HPP) as a substitute or complementary technology for thermal pasteurization. HPP has been used industrially for the pasteurization of high-acid RTE products. Yet, this method is not commonly used for pasteurization of low-acid RTE food products, due primarily to the need of additional heating to thermally inactivate spores, coupled with relatively long treatment times resulting in high processing costs. Practical Application: Food companies would like to adopt novel technologies such as HPP instead of using conventional thermal processes, yet there is a lack of information on spoilage and the shelf-life of pasteurized low-acid RTE foods (by different novel pasteurization methods including HPP) in cold storage. This article provides an overview of the microbial concerns and related regulatory guidelines for the pasteurization of low-acid RTE foods and summarizes the effects of HPP in terms of microbiology (both pathogens and spoilage microorganisms), quality, and shelf-life on low-acid RTE foods. This review also includes the most recent research articles regarding a comparison between HPP pasteurization and thermal pasteurization treatments and the limitations of HPP for low-acid chilled RTE foods.

Moisture Content of Bacterial Cells Determines Thermal Resistance of Salmonella enterica Serotype Enteritidis PT 30.

Salmonella spp. are resilient bacterial pathogens in low-moisture foods. There has been a general lack of understanding of critical factors contributing to the enhanced thermal tolerance of Salmonella spp. in dry environments. In this study, we hypothesized that the moisture content (XW ) of bacterial cells is a critical intrinsic factor influencing the resistance of Salmonella spp. to thermal inactivation. We selected Salmonella enterica serotype Enteritidis PT 30 to test this hypothesis. We first produced viable freeze-dried S. Enteritidis PT 30, conditioned the bacterial cells to different XW s (7.7, 9.2, 12.4, and 15.7 g water/100 g dry solids), and determined the thermal inactivation kinetics of those cells at 80°C. The results show that the D-value (the time required to achieve a 1-log reduction) decreased exponentially with increasing XW We further measured the water activities (aw) of the freeze-dried S. Enteritidis PT 30 as influenced by temperatures between 20 and 80°C. By using those data, we estimated the XW of S. Enteritidis PT 30 from the published papers that related the D-values of the same bacterial strain at 80°C with the aw of five different food and silicon dioxide matrices. We discovered that the logarithmic D-values of S. Enteritidis PT 30 in all those matrices also decreased linearly with increasing XW of the bacterial cells. The findings suggest that the amount of moisture in S. Enteritidis PT 30 is a determining factor of its ability to resist thermal inactivation. Our results may help future research into fundamental mechanisms for thermal inactivation of bacterial pathogens in dry environments.IMPORTANCE This study established a logarithmic relationship between the thermal death time (D-value) of S. Enteritidis PT 30 and the moisture content (XW ) of the bacterial cells by conducting thermal inactivation tests on freeze-dried S Enteritidis PT 30. We further verified this relationship using literature data for S. Enteritidis PT 30 in five low-moisture matrices. The findings suggest that the XW of S. Enteritidis PT 30, which is rapidly adjusted by microenvironmental aw, or relative humidity, during heat treatments, is the key intrinsic factor determining the thermal resistance of the bacterium. The quantitative relationships reported in this study may help guide future designs of industrial thermal processes for the control of S. Enteritidis PT 30 or other Salmonella strains in low-moisture foods. Our findings highlight a need for further fundamental investigation into the role of water in protein denaturation and the accumulation of compatible solutes during thermal inactivation of bacterial pathogens in dry environments.

Stability of Listeria monocytogenes in non-fat dry milk powder during isothermal treatment and storage.

Dry dairy powder is a commonly used ingredient for ready-to-eat foods. It has been implicated in multiple foodborne outbreaks. Listeria monocytogenes can survive in low-moisture conditions for a long duration. However, there is no information on Listeria survival in dry milk powder during storage and thermal treatments. The objectives of this study were to examine the stability of L. monocytogenes in non-fat dry milk (NFDM) during extended storage and further analyze thermal resistance of L. monocytogenes in NFDM under different water activities (aw) and its thermal stability after 1-year storage. We observed approximately 1.75 and 2.93 log CFU/g reduction of L. monocytogenes in aw 0.25 NFDM over 1-year storage at 4 and 22 °C, respectively. Thermal resistance of L. monocytogenes was inversely related to aw, and the inactivation kinetic curves of L. monocytogenes in NFDM at target aw showed a log-linear trend under all tested conditions. For aw 0.25, 0.30, and 0.45 NFDM, the ranges of D-values, were 66.2-21.3, 33.5-9.4, and 14.6-4.3 min at 70, 75 and 80 °C, respectively. The z-values for L. monocytogenes in NFDM at aw 0.25-0.45 were 14.6-16.0 C°. Furthermore, the thermal stability of L. monocytogenes in aw 0.25 NFDM post 6-month or 12-month storage under refrigerated or ambient temperature did not deviate much from that in NFDM prior to the storage. Data indicated that a 60-min heat treatment at 80 °C resulted in ~ 5-log reduction of L. monocytogenes in NFDM of aw 0.30. This provides a promising intervention strategy to enhance bactericidal efficacy of thermal treatment while maintaining the quality of milk powder.

Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella during cocoa powder thermal processing.

Salmonella is capable of surviving in a low moisture environment for long periods. Once adapted to the xeric conditions, the thermal resistance of Salmonella is enhanced. Cocoa powder is a low water activity (aw) food (LawF) that is an essential component in a wide variety of desserts and ready-to-eat (RTE) foods and drinks. The aim of this study was to evaluate the desiccation and thermal resistance of Salmonella in cocoa powder, as well as to examine the suitability of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella during cocoa powder thermal processing. Natural unsweetened cocoa powder was inoculated with a 3-strain Salmonella cocktail or E. faecium and was equilibrated to aw 0.30 and 0.45 at room temperature, then subjected to isothermal treatments at 70-80 °C or 12-month storage at RT (room temperature, 22.0 ±â€¯0.5 °C, aw 0.30). At 70 and 80 °C, D-values of both Salmonella and E. faecium increased with decreasing aw. D-values of Salmonella at aw 0.30 cocoa powder were 46.2 ±â€¯4.7, 20.5 ±â€¯1.7, and 11.5 ±â€¯0.9 min at 70, 75 and 80 °C, respectively. Higher heat resistance of E. faecium in aw 0.30 cocoa powder was observed with D-values of 59.9 ±â€¯5.0, 28.9 ±â€¯1.8, and 16.1 ±â€¯1.4 min at 70, 75, and 80 °C, respectively. However, E. faecium demonstrated less heat resistance than Salmonella when aw was increased to 0.45. D-values for Salmonella at aw 0.45 were 31.6-7.0 min at 70-80 °C compared to 25.8-4.7 min for E. faecium. During 12 months of storage at RT, surviving E. faecium population in aw 0.30 cocoa powder was higher than that of the Salmonella cocktail; the population decreased by 1.39 and 3.75 logs, respectively. These findings indicate that the suitability of E. faecium as a surrogate organism for Salmonella is influenced by aw of cocoa powder. The aw correlates with thermal inactivation rates in both Salmonella and E. faecium, and should be considered as a significant contributor to the thermal resistance of Salmonella in cocoa powder.

Dry inoculation methods for nonfat milk powder.

Carriers with inoculated microorganisms are often used to validate low-moisture food safety interventions. In this study, we evaluated dry inoculation methods using silicon dioxide (SiO2) and a small portion of nonfat milk powder (NFMP) as dry carriers for NFMP. Silicon dioxide was characterized by vapor sorption analysis. One milliliter of inoculum of a 5-strain Salmonella cocktail (serovars Agona, Reading, Tennessee, Montevideo, and Mbandaka) or Enterococcus faecium NRRL B-2354 was inoculated onto 1 g of SiO2 or 10 g of NFMP as carriers. Both inoculated carriers were air-dried for 72 h [22°C, relative humidity (RH) ∼30%], equilibrated to water activity (aw) 0.25 ± 0.02 (24 h at 22°C, RH 25%), and mixed with preconditioned NFMP (aw = 0.25 ± 0.02) to reach an inoculation level of 8.2 ± 0.2 log cfu/g. Inoculated NFMP was stored at 22°C, RH 25%, and its bacterial populations were monitored for 30 d. Both sets in equilibrated NFMP were subjected to isothermal treatments in closed aluminum cells at 85, 90, and 95°C. Silicon dioxide maintained moisture content (0.29 ± 0.03%, dry basis) at different water activities. The NFMP inoculated with both carriers exhibited stable bacterial populations over 30 d at 22°C. Strains in NFMP inoculated with SiO2 showed equal or higher D-values but equal z-values compared with those inoculated with a small portion of NFMP. Enterococcus faecium exhibited comparable thermal resistance to Salmonella under all tested conditions. This study supports E. faecium as a Salmonella surrogate in thermal processing of NFMP and the use of SiO2 to inoculate NFMP.

Natural color pigments: oxidative stability and degradation kinetics during storage in thermally pasteurized vegetable purees.

BACKGROUND: Package oxygen transmission rate (OTR) can affect the stability of natural color pigments such as anthocyanins, betalains and chlorophylls in foods during storage. In the present study, we investigated the oxygen sensitivity of selected pigments in thermally pasteurized vegetable purees held at a refrigeration temperature. We modulated the oxygen ingress in packaging using multilayer films with OTRs of 1, 30 and 81 cm3  m-2  day-1 . Red cabbage, beetroot and pea purees were vacuum packed, pasteurized to achieve a cumulative lethality of P 90 ° C 10 ° C = 12.8-13.4 min and stored at 7 °C for 80 days. RESULTS: Anthocyanins were relatively stable (< 4% losses), regardless of the film OTR. Betalains showed the highest sensitivity to different OTRs, with total losses varying from 4% to 49% at the end of storage and showing significant differences (P < 0.05) among the three films. Chlorophylls showed no significant difference (P > 0.05) in sensitivity to film OTRs. However, continuous degradation of chlorophylls was observed for all film types, with total chlorophyll losses ranging from 33% to 35%. Overall color differences (ΔE) at the end of storage for cabbage, beet and pea puree were between 0.50-1.70, 1.00-4.55 and 7.41-8.08, respectively. Betalains and chlorophylls degradation followed first-order and fractional conversion kinetics, whereas ΔE followed zero-order and fractional conversion kinetics during storage. CONCLUSION: All three pigments behaved differently to oxygen ingress during storage. Low to medium barrier films are suitable for products containing red cabbage anthocyanins. High barrier films are must for betalains, whereas medium to high barrier films are suitable for chlorophyll-containing products. © 2019 Society of Chemical Industry.

Exponentially Increased Thermal Resistance of Salmonella spp. and Enterococcus faecium at Reduced Water Activity.

Salmonella spp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters of Salmonella spp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (aw, treatment temperature) plays an important role in the sharply increased thermal resistance of Salmonella enterica serovar Enteritidis PT 30 and its potential surrogate Enterococcus faecium NRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding aw,80°C values for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model (R2, 0.83 to 0.97). Reductions in the aw,80°C values of bacterial cells exponentially increased the D80°C (the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values for S Enteritidis and E. faecium on silicon dioxide. The log-linear relationship between the D80°C values for each strain in silicon dioxide and its aw,80°C values was also verified for organic wheat flour. E. faecium showed consistently higher D80°C values than S Enteritidis over the aw,80°C range tested. The estimated zaw (the change in aw,80°C needed to change D80°C by 1 log) values of S Enteritidis and E. faecium were 0.31 and 0.28, respectively. This study provides insight into the interpretation of Salmonella thermal resistance that could guide the development and validation of thermal processing of low-moisture foods.IMPORTANCE In this paper, we established that the thermal resistance of the pathogen S Enteritidis and its surrogate Enterococcus faecium, as reflected by D values at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between the D80°C values of each strain in silicon dioxide and its aw,80°C values was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.

Enterococcus faecium as a Salmonella surrogate in the thermal processing of wheat flour: Influence of water activity at high temperatures.

This study investigated the influence of temperature-dependent water activity (aw) on thermal resistances of Enterococcus faecium NRRL B-2354 (E. faecium) and Salmonella Enteritidis PT 30 (S. Enteritidis) in wheat flour. The aw for wheat flour samples at 20, 40, and 60 °C was determined by a vapor sorption analyzer and at 75, 80 and 85 °C using custom-built thermal cells with high temperature humidity sensors. Full-factorial isothermal inactivation studies of both strains in sealed aluminum-test-cells included three temperatures (75, 80, and 85 °C) and three aw,25°C levels (0.30, 0.45 and 0.60 within ±0.02 range, prior to the thermal treatments). Isotherm results of wheat flour demonstrate a significant increase (P < 0.05) of aw as temperature rises (e.g. aw,25°C = 0.45 ±â€¯0.02 became aw,80°C = 0.71 ±â€¯0.02 in a closed system). Inactivation kinetics of both microorganisms fitted a log-linear model, the yielded D-values varied from 2.7 ±â€¯0.2 min (D85°C of S. Enteritidis at aw,25°C 0.60 ±â€¯0.02) to 65.8 ±â€¯2.5 min (D75°C of E. faecium at aw,25°C 0.30 ±â€¯0.02). The zT of E. faecium and S. Enteritidis decreased from 16.4 and 16.9 °C, respectively, to 10.2 °C with increased moisture content (dry basis) from 10 to 14%. Under all tested conditions, E. faecium exhibited equal or higher (1.0-3.1 times) D- and zT-values than those of Salmonella. Overall, E. faecium should be a conservative surrogate for Salmonella in thermal processing of wheat flour for control of Salmonella over a moisture content of 10-14% and treatment temperatures between 75 and 85 °C.

Vacuum impregnation of firming agents in red raspberries.

BACKGROUND: Red raspberries are a delicate and highly perishable fruit with a fragile pulp tissue. In this study we used vacuum impregnation (VI) methods to incorporate pectin and calcium chloride into whole red raspberries to improve their firmness. Specifically, we impregnated low methoxyl pectin (LMP) at 10 g of pectin kg-1 of solution and calcium chloride (CaCl2 ·2H2 O) at 30 g calcium kg-1 of pectin, and on the other side pectin methylesterase (PME) at 10 g of enzyme kg-1 of solution, and (CaCl2 ·2H2 O) at 10 g of calcium kg-1 of solution, into whole red raspberries. We tested three vacuum levels 33.9, 50.8, and 67.8 kPa, three vacuum impregnation times 2, 7, and 15 min, and two temperatures, 20 and 40 °C, during VI treatment. Maximum force (FM ) and gradient (GC3 ) were evaluated to assess raspberry firmness. RESULTS: A vacuum level of 50.8 kPa, processing time of 7 min, and a LMP and calcium infusion at 20 °C resulted in the firmest fruit compared to the other treatments. At these VI treatment conditions, FM and GC3 values of red raspberries obtained were 28 N, and 8.4 N mm-1 , respectively. CONCLUSION: The optimal VI conditions identified in this study can be used to improve firmness and structural integrity of red raspberries by infusion of LMP and calcium. Findings on vacuum-impregnated red raspberries may be used to develop dehydrofrozen berries for incorporation into bakery and dairy products. © 2018 Society of Chemical Industry.

Recent developments in high-quality drying of vegetables, fruits, and aquatic products.

Fresh foods like vegetables, fruits, and aquatic products have high water activity and they are highly heat-sensitive and easily degradable. Dehydration is one of the most common methods used to improve food shelf-life. However, drying methods used for food dehydration must not only be efficient and economic but also yield high-quality products based on flavor, nutrients, color, rehydration, uniformity, appearance, and texture. This paper reviews some new drying technologies developed for dehydration of vegetables, fruits, and aquatic products. These include: infrared drying, microwave drying, radio frequency drying, electrohydrodynamic drying, etc., as well as hybrid drying methods combining two or more different drying techniques. A comprehensive review of recent developments in high-quality drying of vegetables, fruits and aquatic products is presented and recommendations are made for future research.

Thermal pasteurization of ready-to-eat foods and vegetables: Critical factors for process design and effects on quality.

Increasing consumer desire for high quality ready-to-eat foods makes thermal pasteurization important to both food producers and researchers. To be in compliance with the Food Safety Modernization Act (FSMA), food companies seek regulatory and scientific guidelines to ensure that their products are safe. Clearly understanding the regulations for chilled or frozen foods is of fundamental importance to the design of thermal pasteurization processes for vegetables that meet food safety requirements. This article provides an overview of the current regulations and guidelines for pasteurization in the U.S. and in Europe for control of bacterial pathogens. Poorly understood viral pathogens, in terms of their survival in thermal treatments, are an increasing concern for both food safety regulators and scientists. New data on heat resistance of viruses in different foods are summarized. Food quality attributes are sensitive to thermal degradation. A review of thermal kinetics of inactivation of quality-related enzymes in vegetables and the effects of thermal pasteurization on vegetable quality is presented. The review also discusses shelf-life of thermally pasteurized vegetables.

Oxidation-reduction potential and lipid oxidation in ready-to-eat blue mussels in red sauce: criteria for package design.

BACKGROUND: Ready-to-eat in-package pasteurized blue mussels in red sauce requires refrigerated storage or in combination with an aerobic environment to prevent the growth of anaerobes. A low barrier packaging may create an aerobic environment; however, it causes lipid oxidation in mussels. Thus, evaluation of the oxidation-reduction potential (Eh) (aerobic/anaerobic nature of food) and lipid oxidation is essential. Three packaging materials with oxygen transmission rate (OTR) of 62 (F-62), 40 (F-40) and 3 (F-3) cm3 m-2 day-1 were selected for this study. Lipid oxidation was measured by color changes in thiobarbituric acid reactive substances (TBARS) at 532 nm (TBARS@532) and 450 nm (TBARS@450). RESULTS: Significantly higher (P < 0.05) TBARS@532 was found in mussels packaged in higher OTR film. TBARS@450 in mussels packaged with F-62 and F-40 gradually increased during refrigerated storage (3.5 ± 0.5 °C), but remained constant after 20 days of storage for mussels packaged with F-3. The Eh of pasteurized sauce was not significantly affected (P > 0.05) by OTR and remained negative (< -80 mV) during storage. Negative Eh values can support the growth of anaerobes such as Clostridium botulinum. The headspace oxygen concentration was reduced by about 50% from its initial value during pasteurization, and then further declined during storage. The headspace oxygen concentration was higher in trays packaged with higher OTR film. CONCLUSION: Mussels packed with high OTR film showed higher lipid oxidation, indicating that high barrier film is required for packaging of mussels. Pasteurized mussels must be kept in refrigerated storage to prevent growth of anaerobic proteolytic C. botulinum spores under temperature abuse. © 2016 Society of Chemical Industry.

Influence of Water Activity on Thermal Resistance of Microorganisms in Low-Moisture Foods: A Review.

A number of recent outbreaks related to pathogens in low-moisture foods have created urgency for studies to understand the possible causes and identify potential treatments to improve low-moisture food safety. Thermal processing holds the potential to eliminate pathogens such as Salmonella in low-moisture foods. Water activity (aw ) has been recognized as one of the primary factors influencing the thermal resistance of pathogens in low-moisture foods. But most of the reported studies relate thermal resistance of pathogens to aw of low-moisture foods at room temperature. Water activity is a thermodynamic property that varies significantly with temperature and the direction of variation is dependent on the product component. Accurate methods to determine aw at elevated temperatures are needed in related research activities and industrial operations. Adequate design of commercial thermal treatments to control target pathogens in low-moisture products requires knowledge on how aw values change in different foods at elevated temperatures. This paper presents an overview of the factors influencing the thermal resistance of pathogens in low-moisture foods. This review focuses on understanding the influence of water activity and its variation at thermal processing temperature on thermal resistance of pathogens in different low-moisture matrices. It also discusses the research needs to relate thermal resistance of foodborne pathogens to aw value in those foods at elevated temperatures.

Effect of processing on phenolic antioxidants of fruits, vegetables, and grains--a review.

Understanding the influence of processing operations such as drying/dehydration, canning, extrusion, high hydrostatic pressure, pulsed electric field, and ohmic heating on the phytochemicals of fruits, vegetables, and grains is important in retaining the health benefiting properties of these antioxidative compounds in processed food products. Most of the previous investigations in the literature on the antioxidants of fruits, vegetables, and grains have shown that food-processing operations reduced the antioxidants of the processed foods, which is also the usual consumer perception. However, in the last decade some articles in the literature reported that the evaluation of nutritional quality of processed fruits and vegetables not only depend on the quantity of vitamin C but should include analyses of other antioxidant phytochemicals and antioxidant activity. Thermal processing increased the total antioxidant activity of tomato and sweet corn. Most importantly, analysis also depends on the condition, type, and mechanism of antioxidant assays used. This review aims to provide concise information on the influence of various thermal and nonthermal food-processing operations on the stability and kinetics of health beneficial phenolic antioxidants of fruits, vegetables, and grains.

Impacts of water activity on survival of Listeria innocua and Enterococcus faecium NRRL B-2354 in almonds during steam treatments.

Raw almonds have been associated with Salmonella outbreaks and multiple recalls related to Listeria monocytogenes contamination. While steam treatment has been approved for pasteurizing both conventional and organic whole almonds, there is limited understanding of how water activity (aw) influences the effectiveness of steam treatments in decontaminating almonds. Hence, this study aimed to assess and compare the efficacy of steam treatments against Listeria innocua and Enterococcus faecium NRRL B-2354, the known non-pathogenic surrogates, on almonds. It also sought to investigate the impact of almond's aw on bacterial resistance during steam treatments. Almond kernels were inoculated with ~8 log10 CFU/g of either E. faecium or L. innocua and equilibrated to aw 0.25 or 0.45 before being subjected to steam treatments at temperatures of 100-135 °C. Our results revealed that L. innocua exhibited lower resistance to steam compared to E. faecium, with 1.2-2.6 log10 CFU/g reductions for L. innocua and 1.0-2.0 log10 CFU/g reductions for E. faecium when the surface temperature of almonds reached 100-130 °C, depending on the aw of the almonds. The obtained DL. innocua, 100-130°C-values were 2.0-16.6 s, and DE. faecium, 100-130°C-values were 4.0-21.8 s, depending on the aw of almonds. In general, elevating steam temperatures and almond aw decreased the tolerance of L. innocua and E. faecium during steam inactivation. In addition, the z-values indicated that E. faecium on almonds was less sensitive to change in steam temperature compared to L. innocua, especially at lower aw. The zL. innocua-values were 36.6 °C and 35.7 °C, while zE. faecium-values were 48.9 °C and 42.7 °C in almonds with aw 0.25 and 0.45, respectively. Results from this study suggest that steam treatments serve as effective interventions for controlling pathogen contaminations in raw almonds.

Thermal inactivation kinetics of Salmonella and Campylobacter in chicken livers.

Salmonella and Campylobacter are major foodborne pathogens that cause outbreaks associated with contaminated chicken liver. Proper cooking is necessary to avoid the risk of illness to consumers. This study tested the thermal inactivation of a 4-strain Salmonella cocktail and a 3-strain Campylobacter cocktail in chicken livers separately at temperatures ranging from 55.0 to 62.5°C. Inoculated livers were sealed in aluminum cells and immersed in a water bath. The decimal reduction time (D-values) of Salmonella in chicken livers were 9.01, 2.36, 0.82, and 0.23 min at 55.0, 57.5, 60.0, and 62.5°C, respectively. The D-values of Campylobacter ranged from 2.22 min at 55.0°C to 0.19 min at 60.0°C. Salmonella and Campylobacter had similar z-values in chicken livers of 4.8 and 4.6°C, respectively. Chicken livers can be heated to internal temperatures of 70.0 to 73.9°C for at least 1.6 to 0.2 s to achieve a 7-log reduction of Salmonella. Validation tests demonstrated that heating chicken livers to internal temperatures of 70.0 to 73.9°C for 2 to 0 s resulted in a reduction of Salmonella exceeding 7 logs. Collectively, these data show that Salmonella exhibits higher heat resistance than Campylobacter in chicken livers. Therefore, Salmonella could be considered as the target pathogen when designing thermal treatments or cooking instructions for liver products. These findings will aid in designing effective thermal processing for both industrial and home cooking to eliminate Salmonella and Campylobacter, ensuring consumer safety when consuming chicken liver products.

Food Safety Research and Extension Needs for the U.S. Low-Moisture Food Industry.

Historically, low-moisture foods were considered to have minimal microbial risks. However, they have been linked to many high-profile multistate outbreaks and recalls in recent years, drawing research and extension attention to low-moisture food safety. Limited studies have assessed the food safety research and extension needs for the low-moisture food industry. The objectives of this needs assessment were to explore the food safety culture and education needs, identify the food safety challenges and data gaps, and understand the barriers to adopting food-safety-enhancing technologies in the U.S. low-moisture food industry. This needs assessment was composed of two studies. In Study 1, food safety experts from the low-moisture food industry upper management participated in online interviews and a debriefing discussion session. In Study 2, an online anonymous survey was disseminated to a different group of experts with experience in the low-moisture food industry. The qualitative data were analyzed using deductive and inductive coding approaches, while the quantitative data were analyzed via descriptive analysis. Twenty-five experts participated in the studies (Study 1: n=12; Study 2: n=13). Common commodities that participants had worked with included nuts and seeds, spices, flour, and dried fruits and vegetables. A food safety culture conceptual framework was adapted, which included three main components: infrastructure conditions (foundation), individual's food safety knowledge, attitudes, and risk perceptions; and organizational conditions (supporting pillars). Major barriers to establishing a positive food safety culture were identified to be limited resources, difficulties in risk communication, and difficulties in behavioral change. For continual improvement in food safety performance, two major themes of food safety challenges and data gaps were identified: cleaning, sanitation, and hygienic design; and pathogen reduction. Participants perceived the main barriers discouraging the low-moisture food industry from adopting food-safety-enhancing technologies were: (1) budgetary priorities, (2) operation constraints, (3) technology validation, (4) consumer acceptance, and (5) maintaining desired product characteristics such as quality and sensory functionality. The findings of this needs assessment provide guidance for the food industry, academia, and government agencies about the direction of future research and the development of targeted extension programs that might help improve food safety in the low-moisture food industry.

Migration of Chemical Compounds from Packaging Polymers during Microwave, Conventional Heat Treatment, and Storage.

Polymeric packaging protects food during storage and transportation, and withstands mechanical and thermal stresses from high-temperature conventional retort or microwave-assisted food processing treatments. Chemical compounds that are incorporated within polymeric packaging materials to improve functionality, may interact with food components during processing or storage and migrate into the food. Once these compounds reach a specified limit, food quality and safety may be jeopardized. Possible chemical migrants include plasticizers, antioxidants, thermal stabilizers, slip compounds, and monomers. Chemical migration from food packaging is affected by a number of parameters including the nature and complexity of food, the contact time and temperature of the system, the type of packaging contact layer, and the properties of the migrants. Researchers study the migration of food-packaging compounds by exposing food or food-simulating liquids to conventional and microwave heating and storage conditions, primarily through chromatographic or spectroscopic methods; from these data, they develop kinetic and risk assessment models. This review provides a comprehensive overview of the migration of chemical compounds into food or food simulants exposed to various heat treatments and storage conditions, as well as a discussion of regulatory issues.