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Inactivation kinetics of Escherichia coli K12 inoculated in blueberry, grapefruit, cantaloupe, and watermelon juices were evaluated at isothermal temperatures of 52 to 62 °C using thermal death time disks. Juices had variations in titratable acidity, pH, viscosity, and total soluble solids. Survival curves were described by Weibull and linear models, where D‐ and z‐values were determined using the first‐order model. D‐values in watermelon, cantaloupe, blueberry and grapefruit juices, were 6.57–0.64 min, 4.55–0.44 min, 3.94–0.27 min, and 3.03–0.24 min, respectively. The z‐values of E. coli K12 in tested fruit juices ranged from 5.33 to 5.89 °C. While there were no significant differences in the z‐values, the D‐values varied significantly. According to the results obtained, pH and heating temperature dramatically affect the thermal resistance of E. coli K12 under tested conditions. These findings offer a basis for developing predictive models for E. coli inactivation in fruit juices. Practical applications: Thermal death time (TDT) kinetics is extremely useful in ensuring microbial safety of fruit juices. The D‐ and z‐values calculated in this study can contribute to developing predictive models for inactivating E. coli in fruit juices with varied physicochemical attributes. Furthermore, the data and models can be used for optimization of pasteurization processes and regulatory compliance. TDT studies provide the scientific basis for process calculations and help juice manufacturers comply with regulatory requirements. Also, TDT studies help determine the minimal thermal treatments needed to inhibit spoilage organisms, ensuring the juice remains safe and palatable for longer periods. This research will help scientists understand the thermal resistance of E. coli in various fruit juice matrices. [ABSTRACT FROM AUTHOR]

Postconsumer household food residues can act as useful substrates for other industries, but transporting high‐moisture material corresponds to high fuel use and associated greenhouse gas production. Drying food residues at the household level reduces transportation weight, increases stability, and preserves the nutritional quality of recovered material. Mitigating foodborne microbiological safety risks is crucial to encourage the development of novel methods to rapidly dry and stabilize food residues. The objective of this study was to improve the prediction of bacterial pathogen inactivation under various thermal and drying processes in a synthetic mixture of residual food material (RFM). The log reduction rate was measured for Escherichia coli, Enterococcus faecium, and Listeria innocua (surrogates of common foodborne pathogens) in RFM under different moisture contents (12% and 25% by fresh weight) and temperatures (50, 55, and 60°C). Inactivation data were used to determine D‐ and z‐values and to fit a multiple regression model to predict log(D‐values) in response to temperature and moisture content. Across conditions, D‐values were measured to be 5.1–120, 4.6–123, and 32–545 min for E. coli, L. innocua, and E. faecium, respectively. Temperature sensitivities were significantly higher in lower moisture RFM for E. coli and L. innocua. Applying E. coli inactivation models during RFM at 55°C yielded inactivation rates that aligned with experimental values after 5 min (0.1 vs. 0–0.1 logs), 30 min (2.1 vs. 1.3–2.3 logs), and 90 min (7.2 vs. 7.1–8.9 logs). These results can inform the design of RFM drying and stabilization processes to promote pathogen inactivation and safety in downstream applications of dried material. [ABSTRACT FROM AUTHOR]

Heat resistance of bacteria is a factor potentially limiting the production of safety foods. We focused on five Enterobacteriaceae strains related to cheese stretching and sub-pasteurisation experimental temperatures of 50-59 °C. Heat resistance was screened and obtained data were fitted to a classical log-linear model with D-values indicating highly heat-resistant strains used. For example in Klebsiella oxytoca S525, D(50)-value was 96.1 min and D(59)-value 5.1 min. In subsequent detailed measurements, the shape of inactivation curves was sigmoid with defined lag, log-linear and stationary phase. We suggest calculating refined D-values (Dr-values) using only data obtained in log-linear phases, namely Dr(temperature; lag phase). In K. oxytoca S525, the obtained results were: Dr(50; 80.9) = 61.7 min, Dr(53; 12.4) = 36.8 min, Dr(56; < 10) = 10.6 min, and Dr(59; < 3) = 4.3 min. The research of particular inactivation phases can provide interesting findings both in science and industrial practice, especially concerning the passage or persistence of hazardous strains in food processing plants. [ABSTRACT FROM AUTHOR]

A yeast, isolated from grape juice concentrate by a grape juice processing company in central Washington, was subjected to thermal processing in 52° Brix grape juice concentrate, commercial grape juice, and Yeast-Mold (YM) medium to determine D-values and z-values in the search for an effective means of control. At 50 °C in grape juice concentrate the D-value was 33.44 minutes, dropping rapidly as the temperature increased to 52.5 °C, 55 °C, 57.5 °C, and 60 °C. From this data, a z-value was determined to be 4.38 °C. Grape juice and YM broth were similarly tested. Commercial grape juice at 45 °C, 47 °C, and 50 °C showed D-values of 9.80, 7.68, and 1.42, respectively, resulting in a z-value of 5.69 °C. The isolate heat treated in YM broth at 40 °C, 45 °C, 46 °C, 47.5 °C, and 50 °C showed no effect at 40 °C but at higher temperatures, with a D-value of 2.28 at 45 °C, 1.61 at 46 °C, 1.05 at 47.5 °C, and with a z-value of 7.46 °C. This data suggests that an increase in the concentration of sugars in the environment has a protective effect on the yeast against elevated temperatures. Even so, pasteurization at 90 °C for thirty seconds appears to be an effective means of control for the yeast investigated. A yeast with the identical colony and cell morphology was isolated from 52° Brix grape juice concentrate from the same grape juice processing company. Both isolates were subjected to 28S DNA sequencing and FAME analysis for identification and determined to be Zygosaccharomyces rouxii, a known problem yeast in the grape juice and wine-making industry, to this point unknown in the central Washington region. [ABSTRACT FROM AUTHOR]

Background: Cronobacter sspecies are the most significant foodborne pathogen in infant milk formula (IMF). These pathogens have been incriminated in severe forms of neonatal meningitis, sepsis, and necrotizing enterocolitis with a high mortality rate. Aim: This study was performed to elucidate the effect of heat stress on Cronobacter spp. (C. sakazakii and C. pulveris) in reconstituted IMF (RIMF). Methods: The reconstituted formula was inoculated with five C. sakazakii isolates and four C. pulveris isolates separately. The nine isolates of Cronobacter spp. were heated in RIMF at 48°C, 52°C, 56°C, 60°C, 64°C, and 66°C. The D- and z-values were determined by using linear regression analysis. Results: The D-values of all isolates of C. sakazakii (CS1, CS3, CS4, CS5, and CS6) at 48°C, 52°C, 56°C, 60°C, 64°C, and 66°C were in the ranges 7.29-23.47, 2.77-15.50, 0.62-1.04, 0.62-1.02, 0.62-1.00, 0.62-1.00 minutes, respectively; while, the z-values extended from 2.50°C to 4.28°C. The D- values of C. pulveris isolates (CP1, CP2, CP3, CP4) were in the ranges 7.60-22.32, 1.42-8.45, 0.62-1.08, 0.62-0.78, 0.62-0.78, 0.62-0.79 minutes at 48°C, 52°C, 56°C, 60°C, 64°C, 66°C, respectively and the calculated z-values ranged from 3.33°C to 4.89°C. Conclusion: This study may contribute to improving the understanding of the behavior of C. sakazakii and C. pulveris isolates in RIMF at various heat stress temperatures and may participate in the effective control of these pathogens in infant food production. [ABSTRACT FROM AUTHOR]

Hummus is a popular dip in the Middle East region prepared by mixing the boiled chickpeas with tahini and other ingredients, and because its consumption has increased world‐wide some notoriety has developed following an increase in the incidence of hummus‐related illness outbreaks and recalls. The objectives of the current research were (i) to study the efficiency of low dose gamma irradiation to inhibit Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in hummus, and (ii) to assess the effect of environmental stresses namely cold, heat, and desiccation on the resistance of these pathogens to gamma irradiation. The samples of hummus were prepared and then individually inoculated with approximately 7.0 log CFU/g of unstressed or cold‐, heat‐, or desiccated‐stressed cocktail cultures of each of E. coli O157:H7, S. enterica, and L. monocytogenes. The inoculated samples were then exposed to gamma irradiation at doses of 0.1 to 0.6 kGy. The numbers of unstressed E. coli O157:H7, S. enterica, and L. monocytogenes were decreased by 0.6–3.9, 0.7–2.9, and 1.0–3.0 log CFU/g, respectively, by irradiation treatment. The resistance of E. coli O157:H7 to gamma irradiation was not affected by desiccation, heat, and cold stresses. However, the pre‐exposure of S. enterica and L. monocytogenes cells to these stresses reduced their resistance toward gamma irradiation. Practical Application: Gamma irradiation is a non‐thermal treatment that can be used in food processing to ensure food safety and quality. The current study proved that low levels (≤0.6 kGy) of gamma irradiation can effectively decrease the risk of unstressed and cold‐, heat‐, or desiccation‐stressed Salmonella enterica, Listeria monocytogenes, or Escherichia coli O157:H7 in hummus. [ABSTRACT FROM AUTHOR]

The present investigation assesses the influence of cultural attributes and heat and cold treatments on the behavior of native toxigenic L. monocytogenes CFR 1302 and non-toxigenic L. innocua CFR 1304 in selected medium. The growth responses of L. monocytogenes and L. innocua under the influencing factors of storage temperature (10-40°C), pH level (5.5-7.5), and storage period (6-48 h) in brain heart infusion and nutrient broths revealed closeness between observed and predicted populations. Response surface plots were generated for the growth behavior of the two test cultures as a function of pH level. The toxigenic L. monocytogenes CFR 1302 could reach a higher viable population. The effect of heat treatment on Listeria spp. in selected five heating menstra showed the lowest D-value of 3.7 min at 60°C for L. innocua CFR 1304 in Milli-Q water to the highest of 8.4 min at 56°C for L. monocytogenes CFR 1302 in skim milk. The average z-value across the heating menstra for L. monocytogenes was 27.3°C as against that of 22°C for L. innocua. In the case of cold treatment, storage of 4 and 8°C resulted in appreciable increase in counts of L. monocytogenes CFR 1302 from the initial inoculum introduced in selected media. At -20°C, there was a slight decrease in the viable population. The research data helps to predict the viable populations of L. monocytogenes as a part of risk assessment in the food chain. This is of significance in providing safe and healthy food to human population. [ABSTRACT FROM AUTHOR]

Aichi virus (AiV) that results in gastroenteritis worldwide, is spread through contaminated shellfish and water. The resistance/tolerance of AiV to common inactivation processes along with the absence of commercially available vaccines makes it necessary to study its thermal inactivation kinetics. This research evaluated the heat inactivation of AiV in cell‐culture media using 2‐ml sterile glass vials by the linear and Weibull models. Heat treatments of AiV titers of 7 log plaque forming units (PFU)/ml were conducted thrice in a water‐bath at 50, 54, and 58 °C for up to 90 min. Plaque assays for each dilution in duplicate were used to determine infectious virus titers. Linear model D‐values for AiV at 50 ± 1 °C (± = standard error) (come‐up time = 68 s), 54 ± 0.7 °C (130 s), and 58 ± 0.6°C (251 s) were 43.3 ± 4.23 (R2 = 0.40, RMSE = 0.56), 5.69 ± 0.28 (R2 = 0.80, RMSE = 0.43), and 1.20 ± 0.63 min (R2 = 0.69, RMSE = 0.39), respectively, and the linear model z‐value was 5.14 ± 0.39°C (R2 = 0.99, RMSE = 0.08). For the same temperatures, the Weibull model td = 1 values were 20.98 ± 8.8 (R2 = 0.62, RMSE = 0.46, α (scale parameter) = 2.30, β (shape parameter) = 0.38), 3.84 ± 0.69 (R2 = 0.85, RMSE = 0.38, α = 1.08, β = 0.66), and 0.87 ± 0.10 min (R2 = 0.80, RMSE = 0.32, α = 0.22, β = 0.61), respectively and the z‐value (using Td = 1) was 5.79 ± 0.22 °C (R2 = 1.0, RMSE = 0.03). A better fit was obtained with the Weibull model for log reductions versus time with higher R2 and lower RMSE values. Application of AiV inactivation parameters can help reduce the risk of AiV outbreaks. [ABSTRACT FROM AUTHOR]

Intervention technologies for inactivating Salmonella on whole chia seeds are currently limited. Determination of the thermal inactivation kinetics of Salmonella on chia seeds and selection of an appropriate nonpathogenic surrogate will provide a foundation for selecting and optimizing thermal pasteurization processes for chia seeds. In this study, chia seed samples from three separate production lots were inoculated with a five-strain Salmonella cocktail or Enterococcus faecium NRRL-B2354 and equilibrated to a water activity of 0.53 at room temperature (25°C). After equilibration for at least 3 days, the inoculated seeds were subjected to isothermal treatments at 80, 85, or 90°C. Samples were removed at six time points, and surviving bacteria were enumerated. Whole chia seeds were diluted in a filter bag at 1:30 because bacterial recovery with this method was similar to that obtained from ground seeds. Survivor data were fitted to consolidated models: one primary model (log linear or Weibull) and one secondary model (Bigelow). E. faecium had higher thermal resistance than did Salmonella, suggesting that E. faecium may be a suitable conservative nonpathogenic surrogate for Salmonella. The Weibull model was a better fit for the survivor data than was the log-linear model for both bacteria based on the lower root mean square error and corrected Akaike's information criterion values. Lipid oxidation measurements and fatty acid concentrations were significantly different from those of the control samples, but the overall magnitude of the differences was relatively small. The thermal inactivation kinetics of Salmonella and E. faecium on chia seeds may be used as a basis for developing thermal pasteurization processes for chia seeds. [ABSTRACT FROM AUTHOR]

The extraction, purification, and characterization of PME and PG were studied for lemon fruit. Enzymes were partially purified by anion-exchange chromatography using UNOsphere™ Q anion exchanger for lemon PME and DEAE Cellulose anion exchanger for lemon PG. A single band with a fold purity of 20.95 and 15.75 for PME and PG respectively was observed on SDS-PAGE. Molecular weights of partially purified fractions of PME and PG as exhibited by SDS-PAGE were 48 kDa and 95 kDa respectively. Optimum pH and temperature of partially purified lemon PME and PG were pH 9, pH 5 and 45 °C. The crude PME and PG extracts exhibited D-values of 120.57–63.79 and 185.72–29.18 min; Z-values of 15.11 and 16.50 °C; and activation energies (Ea) of 58.23 and 57.18 kJ/mol, respectively. The enzyme stability was not significantly influenced by the fruit matrix as reflected by Z and Ea values. D and Z-values of both the enzymes and microorganisms should be considered while designing thermal treatments to obtain a product with better shelf life. [ABSTRACT FROM AUTHOR]

The Himalayan belt is known for seismic activities; however, activities across this belt are not uniform due to various factors, including stress regime, heterogeneity of subsurface material, and the manner by which the major tectonic Indian plate is colliding with the Eurasian plate. In this study, three sample regions spanning northwest to northeast Himalayas (Kashmir, Nepal, and northeast Himalayan regions) were selected, and their b-values and fractal dimensions from the investigation period of 1973–2015 were calculated. Subsequently, the b-value was calculated via the Gutenberg–Richter relation and maximum likelihood method, whereas the fractal dimension or D-value was calculated using the correlation integral technique. Upon subdividing the time duration into six equal interval subsets, a variation in b-value can be observed over the years. The period 1973–2015 was selected to ensure the sufficiency of data in each subset and an adequate number of subsets for comparisons. From the low b-values, possible high-stress regions and asperities can be inferred, and the variation in stress and heterogeneity of material can be observed from the northwest to northeast Himalayas. An increase in b-value was observed on moving from the northwest to northeast Himalayas during the period of investigation. From the D-value, the extent of the epicentre cluster was observed, revealing that the epicentres were far more clustered to a point in Nepal Himalayas than in the two other regions. The spatial distribution of epicentres was more or less in 1D (fractal dimension) in the northeast and northwest Himalayas, indicating their distribution along particular geological linear features, such as major faults. Hence, a comparative study of the three regions was achieved. On the basis of the b-value, the types of fault and tectonics can be predicted, and the frequency of earthquakes in these Himalayan regions can be better understood. [ABSTRACT FROM AUTHOR]

Egg powders are increasingly popular ingredients, due to their functionality and compactness, in industrial food production and preparation at homes. However, there is a lack of studies that evaluate the thermal resistance of Salmonella Enteritidis PT30 and its potential surrogate Enterococcus faecium NRRL B-2354 in egg powders. This study examined the log-linear relationship between the thermal resistance of Salmonella Enteritidis (D-value) and the water activity (aw) of egg powders. The changes of aw in the egg powders with temperature were measured using a Vapor Sorption Analyzer and a high-temperature cell. The D80 ℃-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, and 0.6) at 20 ℃ were determined using aluminum thermal death test cells. The aw values increased (P < 0.05) in all three egg powders when the temperature of the samples was raised from room temperature to 80 ℃. The D80 ℃-values ranged from 5.3 ± 0.1 to 25.9 ± 0.2 min for S. Enteritidis while 10.4 ± 0.4 to 43.8 ± 0.4 for E. faecium in samples of the three different aw levels. S. Enteritidis PT30 showed a log-linear relationship between D80 ℃-values and aw80 ℃ for the egg powders. This study contributes to our understanding of the impact of aw on the development of thermal treatments for low-moisture foods. [ABSTRACT FROM AUTHOR]

Personalized medicine asks if a new treatment will help a particular patient, rather than if it improves the average response in a population. Without a causal model to distinguish these questions, interpretational mistakes arise. These mistakes are seen in an article by Demidenko that recommends the "D-value," which is the probability that a randomly chosen person from the new-treatment group has a higher value for the outcome than a randomly chosen person from the control-treatment group. The abstract states "The D-value has a clear interpretation as the proportion of patients who get worse after the treatment" with similar assertions appearing later. We show these statements are incorrect because they require assumptions about the potential outcomes which are neither testable in randomized experiments nor plausible in general. The D-value will not equal the proportion of patients who get worse after treatment if (as expected) those outcomes are correlated. Independence of potential outcomes is unrealistic and eliminates any personalized treatment effects; with dependence, the D-value can even imply treatment is better than control even though most patients are harmed by the treatment. Thus, D-values are misleading for personalized medicine. To prevent misunderstandings, we advise incorporating causal models into basic statistics education. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the decimal reduction times (D) and the thermal resistance parameter (z) values of relevant foodborne pathogens linked with fruit juice consumption - namely Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes. Cocktails of different strains of the same bacterial species were prepared and thereafter subjected to thermal inactivation studies at 50, 53, 55, 57, and 60 °C heating temperatures in orange juice. Survivor populations were determined by surface-plating onto a non-selective medium, after which the inactivation behavior and kinetic parameters were determined. Results showed that for all tested organisms, the D-values significantly (P < 0.05) decreased with increasing heating temperature. In all heating temperatures, E. coli O157:H7 exhibited the significantly greatest heat resistance, with D-values ranging from 324.60 s to 95.12 s. At 50 °C, L. monocytogenes (D-values 152.32 s to 11.84 s) was significantly more resistant than S. enterica (D-values 106.55 s to 19.29 s). At higher heating temperatures, the D-values of S. enterica and L. monocytogenes were not significantly different (P > 0.05). The calculated z-values significantly varied across the test organisms, which ranged from 9.40 °C (L. monocytogenes) to 18.78 °C (E. coli O157:H7). These results may be used in the establishment of new, and validation of existing, thermal process schedules to ensure safety against the test pathogens. [ABSTRACT FROM AUTHOR]

The objective of the present study was to evaluate the effect of boiling duration on physicochemical, bioactive compounds, antioxidant activity, color, and texture properties of pumpkin (Cucurbita maxima). The pumpkin was subjected to boiling for 1, 5, 10, and 20 min at 100 ℃. The physicochemical analyses showed that pH, moisture, and water solubility index were increased, whereas ash content was decreased with increasing the boiling time. Prolong boiling exhibited a detrimental effect on bioactive compounds of pumpkin, and it was found that 20 min of boiling caused about 25.91% ± 2.21% loss of total phenolic content, 14.79% ± 1.03% loss of total carotenoids content, and 18.46% ± 1.34% loss of antioxidant activity. A kinetic study was conducted to quantify the losses occurring in bioactive compounds, antioxidant activity, changes in color, and firmness of pumpkin. The study revealed that the logistic model can predict the variation in bioactive compounds and antioxidant activity with higher R2. However, first-order kinetic models were found suitable to predict the changes occurring in bioactive compounds, antioxidant activity, color properties (L*, a*, b*, Chroma), and firmness. The total color changes (ΔE) showed a good fit with zero-order kinetic models (R2 = 0.98). The t1/2 and D-value were calculated for all measured parameters of pumpkin. These findings would be useful in designing thermal processes and related calculations of pumpkin. [ABSTRACT FROM AUTHOR]

Accurate prediction of the thermal destruction rate of foodborne pathogens is important for food processors to ensure proper food safety. When bacteria are subjected to thermal stress during storage, sublethal stresses and/or thermal acclimation may lead to differences in their subsequent tolerance to thermal treatment. The aim of the current study was to evaluate the thermal tolerance of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus that are incubated during overnight growth in tryptic soy broth at four temperatures (15, 25, 35, and 45°C). Following incubation, the bacteria were subjected to thermal treatments at 55, 60, and 65°C. At the end of each treatment time, bacterial survival was quantified and further calculated for the thermal death decimal reduction time (D‐value) and thermal destruction temperature (z‐value) using a linear model for thermal treatment time (min) vs. microbial population (Log CFU/ml) and thermal treatment temperature (°C) vs. D‐value, respectively, for each bacterium. Among the four bacterial species, E. coli generally had longer D‐values and lower z‐values than did other bacteria. Increasing patterns of D‐ and z‐values in Listeria were obtained with the increment of incubation temperatures from 15 to 45°C. The z‐values of Staphylococcus (6.19°C), Salmonella (6.73°C), Listeria (7.10°C), and Listeria (7.26°C) were the highest at 15, 25, 35, and 45°C, respectively. Although further research is needed to validate the findings on food matrix, findings in this study clearly affirm that adaptation of bacteria to certain stresses may reduce the effectiveness of preservation hurdles applied during later stages of food processing and storage. [ABSTRACT FROM AUTHOR]

Improper food processing is one of the major causes of foodborne illness. Accurate prediction of the thermal destruction rate of foodborne pathogens is therefore vital to ensure proper processing and food safety. When bacteria are subjected to pH and thermal stresses during growth, sublethal stresses can occur that may lead to differences in their subsequent tolerance to thermal treatment. As a preliminary study to test this concept, the current study evaluated the effect of prior pH and thermal stresses on thermal tolerance of Salmonella and Staphylococcus using a tryptic soy broth supplemented with yeast extract. Bacteria incubated at three pH values (6.0, 7.4, and 9.0) and four temperatures (15, 25, 35, and 45°C) for 24 hr were subjected to thermal treatments at 55, 60, and 65°C. At the end of each treatment time, bacterial suspensions were surface‐plated on standard method agar for quantification of bacterial survival and further calculation of the thermal death decimal reduction time (D‐value) and thermal destruction temperature (z‐value). The effect of pH stress alone during the incubation on the thermal tolerance of both bacteria was generally insignificant. An increasing pattern of D‐value was observed with the increment of thermal stress (incubation temperature). The bacteria incubated at 35°C required the highest z‐value to reduce the 90% in D‐values. Staphylococcus mostly displayed higher tolerance to thermal treatment than Salmonella. Although further research is needed to validate the current findings on food matrices, findings in this study clearly affirm that adaptation of bacteria to certain stresses may reduce the effectiveness of preservation procedures applied during later stage of food processing and storage. [ABSTRACT FROM AUTHOR]

Human noroviruses (HNoVs) cause significant gastrointestinal disease outbreaks worldwide. Tulane virus (TV) is a cultivable HNoV surrogate widely used to determine control measures against HNoVs. The objective of this study was to determine the heat inactivation kinetics (D‐ and z‐values) of TV in cell‐culture media and on spiked homogenized spinach using the first‐order and Weibull models. TV in cell‐culture media at approximately 7 log PFU/mL (PFU—plaque forming unit) in 2‐mL glass vials was heated at 52, 54, and 56 °C for up to 10 min in a circulating water bath. Survivors were enumerated using confluent host LLC‐MK2 cells in six‐well plates by plaque assay. Data from three replicate treatments assayed in duplicate were analyzed statistically. D‐values by the first‐order model for TV in cell‐culture media at 52, 54, and 56 °C were 4.59 ± 0.05, 2.91 ± 0.05, and 1.74 ± 0.07 min, respectively, with a z‐value of 9.09 ± 0.01 °C (R2 = 0.997). The Weibull model showed td = 1 values of 2.53 ± 0.08, 1.99 ± 0.10, and 0.57 ± 0.64 min, respectively, at the same temperatures. The D‐values for TV in spinach were 7.94 ± 0.21, 4.09 ± 0.04, and 1.43 ± 0.02 min and the z‐value was 10.74 ± 0.01 °C (R2 = 0.98) by the first‐order model and 4.89 ± 0.02, 3.21 ± 0.45, and 0.25 ± 0.38 min for the Weibull model at 50, 54, and 58 °C, respectively. In comparison to previously reported results for the cultivable HNoV surrogate, murine norovirus ‐1, TV in cell‐culture media and spiked on spinach homogenates showed lower D‐ and z‐values. TV may not be an ideal HNoV surrogate for heat inactivation studies in cell‐culture media or homogenized spinach in vacuum bags. [ABSTRACT FROM AUTHOR]

Salmonella can survive in low-moisture, high-protein, and high-fat foods for several years. Despite nationwide outbreaks and recalls due to the presence of Salmonella in low-moisture foods, information on thermal inactivation of Salmonella in these products is limited. This project evaluated the impact of water activity (aw), temperature, and food composition on thermal inactivation of Salmonella enterica serovar Agona in defined high-protein and high-fat model food matrices. Each matrix was inoculated with Salmonella Agona and adjusted to obtain a target aw, ranging from 0.50 to 0.98. Samples were packed into aluminum test cells and heated (52 to 90°C) under isothermal conditions. Survival of Salmonella Agona was detected on tryptic soy agar with 0.6% yeast extract. Complex influences by food composition, aw, and temperature resulted in significantly different ( P < 0.05) thermal resistance of Salmonella for the conditions tested. It was estimated that the same point temperatures at which the D-values of the two matrices at each aw (0.63, 0.73, 0.81, and 0.90) were identical were 79.48, 71.28, 69.62, and 38.42°C, respectively. Above these temperatures, the D-values in high-protein matrices were larger than the D-values in high-fat matrices at each aw. Below these temperatures, the inverse relationship was observed. A correlation between temperature and aw existed on the basis of the level of fat or protein in the food, showing that these compositional factors must be accounted for when predicating thermal inactivation of Salmonella in foods. [ABSTRACT FROM AUTHOR]

Precooking of tuna is a potential critical control point (CCP) in the commercial manufacturing of canned tuna. To assess the efficacy of precooking as a CCP, an understanding of the thermal properties of histamine-producing bacteria (HPB) and their histidine decarboxylase (HDC) enzymes is required. The thermal properties of many HPB have been determined, but the thermal resistances of the HDC enzymes are unknown. The purpose of this study was to determine the D- and z-values of selected HDC enzymes to evaluate the CCP of precooking during the canning process and provide scientific data to support U.S. Food and Drug Administration guidelines. HDC (hdc) genes from three strains each of Morganella morganii,Enterobacter aerogenes,Raoultella planticola, and Photobacterium damselae were cloned, expressed, and purified using the Champion pET Directional TOPO Expression System, pET100 cloning vector, and HisPur Cobalt resin. The heat resistances of all enzymes were compared at 50°C, and the D- and z-values from one strain of each HPB were determined at 50 to 60°C. To evaluate the heat inactivation of HDC enzymes during canned tuna processing, tuna tissue was inoculated with HDCs and heated to 60°C in a water bath set at 65 and 100°C. The D-values for the HDC enzymes from M. morganii,E. aerogenes,R. planticola, and P. damselae ranged from 1.6 to 4.1, 1.6 to 6.3, 1.9 to 4.3, and 1.6 to 2.9 min, respectively, at 50 to 60°C. The z-values for M. morganii,E. aerogenes,R. planticola, and P. damselae were 19.2, 18.0, 22.0, and 13.3°C, respectively. The HDCs from all HPB except E. aerogenes showed no significant activity after being heated to 60°C. The data generated in this study will help refine current guidelines for the thermal destruction of the HDC enzymes. [ABSTRACT FROM AUTHOR]

BACKGROUND The extraction, purification, and characterisation of peroxidase ( POD) and polyphenol oxidase ( PPO) were studied for Kalipatti sapota fruit. The crude enzyme extract was partially purified by ammonium sulfate precipitation followed by BioGel P100 size exclusion and Unosphere Q anion-exchange chromatography. RESULTS Molecular weights of 20 kDa ( POD) and 24 kDa ( PPO) were indicated by SDS-PAGE. A single band was observed on SDS-PAGE with a fold purity of 10.38 and 7.42 for POD and PPO, respectively. Michaelis-Menten constants for POD and PPO were 22.3 and 23.0 mmol L−1 using guaiacol and catechol as substrates. Thermal inactivation kinetics was studied in the temperature range of 60-95 °C. The crude extract of POD and PPO showed D-values of 2.2-60.2 and 1.0-35.2 min; Z-values of 18.7 ± 0.4 and 16.0 ± 0.3 °C; and activation energies ( Ea) of 128.6 and 151.0 kJ mol−1, respectively. CONCLUSION POD and PPO showed good stability over a wide range of pH and temperature. As reflected by Z and Ea values, the fruit matrix had no significant influence towards enzyme stability. Designing of thermal process should take into consideration D- and Z-values of the enzymes along with D- and Z-values of microorganisms to obtain a product with better shelf life. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Food-grade galactooligosaccharide (GOS) with low water activity (aw of ca. 0.7) is used as an ingredient in various foods. We evaluated heat tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici at temperatures (70 to 85°C) used during the saturation process of GOS by comparing decimal reduction time (D-values) and thermal resistance constants (z-values). To determine the D- and z-values, GOS containing Salmonella (5.1 to 5.8 log CFU/g) or C. sakazakii (5.3 to 5.9 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 40, 25, or 15 s, respectively, and GOS containing P. acidilactici (6.1 to 6.5 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 150, 75, or 40 s, respectively. The D-values were calculated using a linear model for heating time versus microbial population for each bacterium. When the D-values for Salmonella, C. sakazakii, and P. acidilactici in GOS were compared, the thermal resistance of all bacteria decreased as the temperature increased. Among the three bacteria, P. acidilactici had higher D-values than did Salmonella and C. sakazakii. The z-values of Salmonella, C. sakazakii, and P. acidilactici were 30.10, 33.18, and 13.04°C, respectively. Overall order of thermal resistance was P. acidilactici > Salmonella ≈ C. sakazakii. These results will be useful for selecting appropriate heat treatment conditions for the decontamination of pathogenic microorganisms during GOS manufacturing. [ABSTRACT FROM AUTHOR]

The objectives of this work were to study the ultrasound- and ultraviolet light-induced inactivation kinetics of polyphenol oxidase extracted from different sources in a model system. The polyphenol oxidase crude extract was obtained from bananas, apples, quince, eggplants, plums, dill, and cultured mushrooms, which exhibited high enzyme activity. The polyphenol oxidase crude extract was treated with ultrasound and ultraviolet light at 40°C temperature for 40 min. The study showed that the polyphenol oxidase enzyme was inactivated between 12 and 100% during ultrasound only treatment; between 4 and 29% during ultraviolet light only treatment; and between 80 and 100% during simultaneous ultrasound and ultraviolet light treatment. Based on the measurements, an exponential decay model for determining polyphenol oxidase inactivation kinetics was developed. The model provides high determination coefficients (R2): 0.968–0.999 with ultrasound only treatment, 0.881–0.990 with ultraviolet only treatment, and 0.975–1.000 with simultaneous ultrasound and ultraviolet treatment. The polyphenol oxidase kinetics evaluation showed that different treatments provided different inactivation times, orD-values. TheD-values were 7.0–656.1 min for ultrasound only treatment (DUS), 251–1887 min for ultraviolet only treatment (DUV), and 3.3–59.4 min for combined ultrasound and ultraviolet treatment (DUS+UV). [ABSTRACT FROM AUTHOR]

This study was conducted to validate a simulated commercial baking process for hamburger buns to destroy Salmonella serovars and to determine the appropriateness of using nonpathogenic surrogates (Enterococcus faecium ATCC 8459 or Saccharomyces cerevisiae) for in-plant process validation studies. Wheat flour was inoculated (~6 log CFU/g) with three Salmonella serovars (Typhimurium, Newport, or Senftenberg 775W) or with E. faecium. Dough was formed, proofed, and baked to mimic commercial manufacturing conditions. Buns were baked for up to 13 min in a conventional oven (218.3°C), with internal crumb temperature increasing to ~100°C during the first 8 min of baking and remaining at this temperature until removal from the oven. Salmonella and E. faecium populations were undetectable by enrichment (>6-log CFU/g reductions) after 9.0 and 11.5 min of baking, respectively, and ≥5-log-cycle reductions were achieved by 6.0 and 7.75 min, respectively. D-values of Salmonella (three-serovar cocktail) and E. faecium 8459 in dough were 28.64 and 133.33, 7.61 and 55.67, and 3.14 and 14.72 min at 55, 58, and 61°C, respectively, whereas D-values of S. cerevisiae were 18.73, 5.67, and 1.03 min at 52, 55, and 58°C, respectively. The z-values of Salmonella, E. faecium, and S. cerevisiae were 6.58, 6.25, and 4.74°C, respectively. A high level of thermal lethality was observed for baking of typical hamburger bun dough, resulting in rapid elimination of high levels of the three-strain Salmonella cocktail; however, the lethality and microbial destruction kinetics should not be extrapolated to other bakery products without further research. E. faecium demonstrated greater thermal resistance compared with Salmonella during bun baking and could serve as a conservative surrogate to validate thermal process lethality in commercial bun baking operations. Low thermal tolerance of S. cerevisiae relative to Salmonella serovars limits its usefulness as a surrogate for process validations. [ABSTRACT FROM AUTHOR]

Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and optoelectronic properties. Al atoms are found to substitute the host Zn whereas Cu dopants mainly segregate in grain boundaries and thereby determine the optical properties. The undoped as well as Al and Cu doped ZnO exhibit spherical well defined particles. The spherical nanoparticles change to rod type structures on co-doping. The average particle size decreases on doping what consequently results in an increment in band gap. Blue shift in UV absorption is governed by the functional group of glucose; further blue shift occurring on metal doping may be attributed to Burstein-Moss effect. PL spectra of doped and undoped ZnO show a dominant near band gap UV emission along with visible emission owing to the defects. The PL peak intensity increases on doping with Cu and Al. The linear I-V characteristics indicate the ohmic behavior of ZnO nanostructures. [ABSTRACT FROM AUTHOR]

Listeria monocytogenesresults in potential food safety concerns in ready-to-eat refrigerated products. Cold-smoked salmon is a food considered to be at high risk forListeriaspp. contamination for which a mild heat treatment or pasteurization step might be helpful to reduce microbial levels. Cold-smoked salmon was inoculated with a cocktail of four strains (L. monocytogenes: ATCC19114, 7644, and 19113, andL. innocua: ATCC51742) and inactivation curves obtained at 58, 60, 62, 64, and 66°C using capillary tube methods. Inactivation results showed typical log linear trends (R2≥ 0.97).D-values ofL. monocytogenesandL. innocuawere 0.3 to 14.1 min at 66 to 58°C, with az-value of 5.2 to 6.5°C and activation energy of 332 to 414 kJ/mol. The nonpathogenicListeria innocuaATCC51742 had comparableD- andz-values to the three strains ofL. monocytogenesand thus can be used for validation of pasteurization processes to controlL. monocytogenesin cold-smoked salmon and potentially other ready-to-eat thermolabile food products. [ABSTRACT FROM PUBLISHER]

Aims Epidemiological evidence suggests that hepatitis A virus ( HAV) is the most common pathogen transmitted by bivalve molluscs such as clams, cockles, mussels and oysters. This study aimed to generate thermal inactivation kinetics for HAV as a first step to design adequate thermal processes to control clam-associated HAV outbreaks. Methods and Results Survivor curves and thermal death curves were generated for different treatment times (0-6 min) at different temperatures (50-72°C) and Weibull and first-order models were compared. D-values for HAV ranged from 47·37 ± 1·23 to 1·55 ± 0·12 min for the first-order model and 64·43 ± 3·47 to 1·25 ± 0·45 min for the Weibull model at temperatures from 50 to 72°C. z-Values for HAV in clams were 12·97 ± 0·59°C and 14·83 ± 0·0·28°C using the Weibull and first-order model respectively. The calculated activation energies for the first-order and Weibull model were 145 and 170 kJ mole−1 respectively. Conclusion The Weibull model described the thermal inactivation behaviour of HAV better than the first-order model. Significance and Impact of the Study This study provides novel and precise information on thermal inactivation kinetics of HAV in homogenized clams. This will enable reliable thermal process calculations for HAV inactivation in clams and closely related seafood. [ABSTRACT FROM AUTHOR]

Aim: The intent of this study is to decontaminate Bacillus endospores and to determine the D-values using silver nanoparticles (AgNPs) synthesized from Streptomyces sp. cell filtrate. Materials & methods: AgNPs synthesis was performed extracellularly followed by characterization using spectrophotometer, High Resolution Transmission Electron Microscope and x-ray diffraction pattern analysis. Subsequently, the optimized conditions for the decontamination and D-value estimation of Bacillus endospores were determined using the response surface methodology. The environmental spore decontamination study was performed in mice model. Results: AgNPs were visibly and spectroscopically identified which were spherical with the size range of less than 20 nm. The synthesized AgNPs destroyed 1log10 CFU Bacillus endospores at around 20 min. The adherence of AgNPs to the surface of spore coat, pit formation and its complete structural loss was detected under field emission scanning electron microscopy. All the mice exposed to AgNP-treated spores showed no sign of pathological lesions. Conclusion: The results of our study strongly suggest that the application of AgNPs as a sporicidal agent could be a new approach in consistently eliminating the hazardous Bacillus spores. [ABSTRACT FROM AUTHOR]

In current clustering processing algorithms of histogram publishing based on differential privacy preserving, there was not algorithm which differentiate between histogram counts with smaller variance and histogram counts with larger variance. And it caused the waste of algorithm complexity when dealing with histogram with smaller variance. This paper proposed a segmentation algorithm based on the D-value of adjacent bins. It determined the segmentation boundary through calculating the D-value of adjacent unit bins and then determined the feasibility of each division based on the sum value of reconstruction error and the amount of noise. It verified the effectiveness of the proposed algorithm through the experimental simulation and theoretical analysis. This algorithm ensures the accuracy of data released. What's more important is that it greatly improves the efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

Thermal treatment at temperatures between 46.0°C and 55.0°C was evaluated as a method for sanitization of organic waste, a temperature interval less commonly investigated but important in connection with biological treatment processes. Samples of dairy cow feces inoculated withSalmonellaSenftenberg W775,Enterococcus faecalis, bacteriophage ϕX174, and porcine parvovirus (PPV) were thermally treated using block thermostats at set temperatures in order to determine time-temperature regimes to achieve sufficient bacterial and viral reduction, and to model the inactivation rate. Pasteurization at 70°C in saline solution was used as a comparison in terms of bacterial and viral reduction and was proven to be effective in rapidly reducing all organisms with the exception of PPV (decimal reduction time of 1.2 h). The results presented here can be used to construct time-temperature regimes in terms of bacterial inactivation, with D-values ranging from 0.37 h at 55°C to 22.5 h at 46.0°C and 0.45 h at 55.0°C to 14.5 h at 47.5°C forSalmonellaSenftenberg W775 andEnterococcus faecalis, respectively and for relevant enteric viruses based on the ϕX174 phage with decimal reduction times ranging from 1.5 h at 55°C to 16.5 h at 46°C. Hence, the study implies that considerably lower treatment temperatures than 70°C can be used to reach a sufficient inactivation of bacterial pathogens and potential process indicator organisms such as the ϕX174 phage and raises the question whether PPV is a valuable process indicator organism considering its extreme thermotolerance. [ABSTRACT FROM PUBLISHER]

This study was conducted to investigate the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of selected essential oils (EOs) against Escherichia coli 0157:H7 under neutral and acidic pH conditions, and to evaluate the efficacy of EOs on the inactivation of E. coli 0157:H7 in vegetable juice samples stored at 5, 20 and 35°C or heated at 55°C. The growth and survival of E. coli 0157:H7 were significantly affected by pH adjustment, additive concentration, storage temperature and time. A synergistic or hurdle effect was observed within EOs at pH 4.0 and pH 4.5, or with heat treatment. The calculated decimal reduction times (D-value, min) varied with the EOs concentration. Star anise oil (0.05%, vol/vol) provided the maximum reduction in D55 value, from 5.69 min to 0.38 min. The combination of mild heat treatment and EOs may be used to enhance the safety of juice products. [ABSTRACT FROM AUTHOR]

The effect of aluminium cookware on inactivation of Escherichia coli in milk was studied. Samples in aluminium and stainless-steel cups were heated at 60, 63, 65 and 67°C and held at those temperatures for 25, 5, 3 and 2 min, respectively. Results obtained under the temperature of 65 and 67°C clearly showed that cells of E. coli were killed more rapidly in aluminium cups than in stainless-steel cups. D-values in the aluminium cups were significantly shorter than those in stainless-steel cups, especially at higher temperatures. Samples in aluminium cups revealed a better trend inactivation effect than in stainless-steel cups at 60 and 63°C, however, there were no significant difference. Considering on z-values, results which obtained by aluminium cups were slightly lower than that obtained by stainless-steel cups. These results indicate that an aluminium utensil has an inactivating effect on E. coli and that rate of inactivation increases as temperature increases. [ABSTRACT FROM AUTHOR]

The kinetics of thermal degradation of ascorbic acid in fluted pumpkin leaves were investigated from 60 to 90°C (pH 5.0 to 6.5). Ascorbic acid degradation was modeled as a first order rate reaction with the rate constants increasing with increase in pH of the medium. The pH and temperature dependence of the rates of destruction gave highly significant correlations when analyzed by the thermal resistance and activated complex reaction rate methods. Activation energy (Ea) ranged from 41.2 to 18.2 kJ/mol while D-values ranged from 103.3 to 22.4 min. The changes in activation energy affected K values which ranged from 5.98 × 10 to 41.7 min. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the application of established D-value calculations to survival curves for various bacteria using the following antimicrobials: acidified sodium chlorite, triclosan, octanoic acid, and sodium hydroxide. D-values can be calculated in 3 ways, a linear regression, an endpoint calculation, or an average of multiple endpoint calculations. The assumption made in calculating a D-value is that the rate of kill follows 1st-order kinetics under specified treatment conditions. Each antimicrobial solution was challenged with approximately 108 CFU/mL of Staphylococcus aureus, Listeria monocytogenes, Salmonella enterica subsp. enterica, and Escherichia coli independently and in triplicate. Test systems were sampled at each of the 10 time points over a period of 7 min, neutralized, pour plated then incubated at 35 °C for 48 h (AOAC official method 960.09). Survival curves using the log-transformed data were calculated using regression analysis. Correlations coefficients for all linear regression analyses ranged between 0.291 and 0.982, with 6 of the 16 different treatment systems having an R2 value below 0.7. Methods used for calculating D-values should lead to the same result if the survival curve in a given condition is linear. The calculated D-values were different using endpoint analysis (Stumbo method), linear regression, and average of multiple endpoints. This study demonstrates the nonlinearity of inactivation curves of antimicrobials. D-value estimations cannot be reliably used to illustrate biocidal activity in antimicrobial test systems. [ABSTRACT FROM AUTHOR]

The survival of bifidobacteria in simulated conditions of the gastrointestinal (GI) tract was studied based on the D- and z-value concept. Some Bifidobacterium spp. are probiotics that improve microbial balance in the human GI tract. Because they are sensitive to low pH and bile salt concentrations, their viability in the GI tract is limited. The D- and z-value approach was therefore adopted as a result of observing constant log-cell reduction (90%) when Bifidobacterium spp. were exposed to these 2 different stressing factors. Survivals of one strain each or 4 species of Bifidobacterium was studied at pH between 3.0 and 4.5 and in ox-bile between 0.15% and 0.60% for times up to 41 h. From the Dacid- and Dbile-values, the order of resistance to acid and bile was B. bifidum > B. infantis > B. longum > B. adolescentis. While the former 3 strains retained high cell viability at pH 3.5 (>5.5 log CFU/mL after 5 h) and at elevated bile salt concentration of 0.6% (>4.5 log CFU/mL after 3 h), B. adolescentis was less resistant (<3.4 log CFU/mL). The zacid- and zbile-values calculated from the Dacid- and Dbile-values ranged from 1.11 to 1.55 pH units and 0.40% to 0.49%, respectively. The results suggest that the Dacid-, Dbile-, zacid-, and zbile-value approach could be more appropriate than the screening and selection method in evaluating survival of probiotic bacteria, and in measuring their tolerance or resistance to gastric acidity and the associated bile salt concentration in the small intestine. Practical Application: The evaluation of the tolerance of bifidobacteria to bile salts and low pH has been made possible by use of D- and z-value concept. The calculated zacid- and zbile-values were all fairly similar for the strains used and suggest the effect of increasing the bile salt concentration or decreasing the pH on the Dacid- and Dbile-values. This approach would be useful for predicting the suitability of bifidobacteria and other lactic acid bacteria (LAB) as probiotics for use in real-life situations. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the influence of temperature (85, 90, 95 and 100 °C), total soluble solids (SS: 10 and 20°Brix or % by weight of sucrose) and pH (3.5 and 4.0) on decimal reduction time ( D-value) of the Alicyclobacillus acidoterrestris strain DSM2498 spores in apple juice, orange juice and malt extract broth (MEB). The effects of SS and pH on D-values and z-values in each media were insignificant ( P > 0.05). In apple juice, orange juice and MEB, z-values of A. acidoterrestris for pH 3.5 and pH 4.0 were 12.2 ± 1.3–14.2 ± 3.2 °C, 11.2 ± 0.3–9.4 ± 0.0 °C and 11.9 ± 0.8–10.3 ± 0.4 °C, respectively. z-values of apple juice, orange juice and MEB samples with SS = 10°Brix and SS = 20°Brix were 14.1 ± 3.2–12.2 ± 1.3 °C, 10.2 ± 0.7–10.5 ± 1.1 °C and 11.3 ± 1.5–10.9 ± 0.2 °C, respectively. However, D-values of all samples were affected by temperature significantly ( P < 0.01). Average D-values of apple juice, orange juice and MEB were 101.2 ± 14.7, 34.4 ± 7.9, 20.3 ± 4.9 and 4.3 ± 1.3 min for 85, 90, 95 and 100 °C. This study demonstrated that A. acidoterrestris spores exhibited high resistance to thermal processing applications. pH and SS of the media did not affect thermal resistance. [ABSTRACT FROM AUTHOR]

Copyright of Dairy Science & Technology (EDP Sciences) is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Dairy Science & Technology (Springer Science & Business Media B.V.) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes in iceberg lettuce by aqueous chlorine dioxide (ClO2) treatment was evaluated. Iceberg lettuce samples were inoculated with approximately 7 log CFU/g of E. coli O157:H7, S. typhimurium, and L. monocytogenes. Iceberg lettuce samples were then treated with 0, 5, 10, or 50 ppm ClO2 solution and stored at 4 °C. Aqueous ClO2 treatment significantly decreased the populations of pathogenic bacteria on shredded lettuce ( P < 0.05). In particular, 50 ppm ClO2 treatment reduced E. coli O157:H7, S. typhimurium, and L. monocytogenes by 1.44, 1.95, and 1.20 log CFU/g, respectively. The D10-values of E. coli O157:H7, S. typhimurium, and L. monocytogenes in shredded lettuce were 11, 26, and 42 ppm, respectively. The effect of aqueous ClO2 treatment on the growth of pathogenic bacteria during storage was evaluated, and a decrease in the population size of these pathogenic bacteria was observed. Additionally, aqueous ClO2 treatment did not affect the color of lettuce during storage. These results suggest that aqueous ClO2 treatment can be used to improve the microbial safety of shredded lettuce during storage. [ABSTRACT FROM AUTHOR]

Enterobacter sakazakii is an opportunistic foodborne pathogen that has been isolated from powdered infant milk formula. This study determined the effect of desiccation, starvation, heat and cold stresses on the thermal inactivation of E. sakazakii in rehydrated infant milk formula (RIMF). Stressed cells were mixed with RIMF at 52, 54, 56, and 58 °C for various time periods. The D- and z-values were determined by using linear regression analysis. D-values for unstressed E. sakazakii at 52, 54, 56, and 58 °C were 15.33, 4.53, 2, and 0.53 min, respectively. Desiccation and heat stresses, but not starvation or cold stress, caused significant ( P < 0.05) reduction in D-values. The z-values of desiccated, starved, heat stressed, and cold stressed E. sakazakii were not significantly different from unstressed cells (4.22 °C). Thermal resistance of E. sakazakii in RIMF is affected by the environmental stresses; that is, desiccation and heat stresses that may surround the bacterium prior to the contamination of infant formula. The results of this study may be of use to regulatory agencies, infant milk producers, and infant caregivers to design heating processes to eliminate E. sakazakii that may be present in infant milk formula. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation. Methods and Results: Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7·5 kGy. The D10-values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0·82 to 1·95 kGy. Conclusions: Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation. Significance and Impact of the Study: Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment. [ABSTRACT FROM AUTHOR]

Water activity ( aw) of ground beef, chicken breast meat, and trout fillets was modified to intermediate ( aw 0.98–0.99) and lowest ( aw 0.94–0.96) levels. The meat samples with modified and unaltered (native, aw 1.00) aw were inoculated with Escherichia coli O157:H7 and subjected to electron beam (e-beam). Survivor curves were plotted and the D10-values were calculated. The D10-values ranged from 0.22 kGy for trout at native aw to 0.33 kGy for beef at intermediate, and chicken and trout at lowest aw. Regardless of the species, aw reduction increased E. coli resistance to e-beam, suggesting that even small depletion of unbound water from food increases survival. The difference of the D10-values between the samples at intermediate and lowest aw was insignificant. E-beam could be used before aw-reducing techniques are applied to food products. However, this would require stringent microbial control following e-beam processing. The ‘tailing’ of survivors was observed for some samples with reduced aw. [ABSTRACT FROM AUTHOR]

Aims: To examine the effect of processing with superheated steam (SS) on Geobacillus stearothermophilus ATCC 10149 spores. Methods and Results: Two inoculum levels of spores of G. stearothermophilus were mixed with sterile sand and exposed to SS at 105–175°C. The decimal reduction time (D-value) and the thermal resistance constant (z-value) were calculated. The effect of cooling of spores between periods of exposure to SS was also examined. A mean z-value of 25·4°C was calculated for both inoculum levels for SS processing temperatures between 130°C and 175°C. Conclusions: Spore response to SS treatment depends on inoculum size. SS treatment may be effective for reduction in viability of thermally resistant bacterial spores provided treatments are separated by intermittent cooling periods. Significance and Impact of the Study: There is a need for technologies that require short thermal processing times to eliminate bacterial spores in foods. The SS processing technique has the potential to reduce microbial load and to modify food texture with less energy in comparison to commonly used hot air treatment. This work provides information on the effect of SS processing parameters on the viability of G. stearothermophilus spores. [ABSTRACT FROM AUTHOR]

The ionic strengths (IS) of ground beef, chicken meat, and trout fillets were modified to intermediate and highest with 3.5% and 7.0% NaCl, respectively. The samples with modified and unaltered (native) IS were inoculated with Escherichia coli O157:H7 and subjected to electron beam (e-beam). The water activity ( aw) of the meat samples were 1.0, 0.96–0.97, and 0.94 for native, intermediate, and highest IS. The D10-values were calculated from survivor curves. The D10-values for E. coli ranged from 0.19 kGy in trout (highest IS) to 0.31 kGy in beef and chicken (highest IS). Regardless of the meat type, the increased resistance of E. coli to e-beam was only observed at the highest IS. The difference of the D10-value for E. coli in samples at intermediate and native IS was insignificant. Regardless of the IS, the E. coli in trout was most sensitive, while the difference of E. coli resistance to e-beam in ground beef and chicken meat was insignificant. [ABSTRACT FROM AUTHOR]

p. yaghmaee and t.d. durance. 2004.To study the effect of 2450 MHz microwave radiation under vacuum (vacuum microwave or VM) on survival and injury ofEscherichia coliand to search for possible nonthermal effects associated with VM.Destruction kinetics ofE. coliin peptone water were determined in a continuous-flow vacuum system, heated by convection heating in a water bath or with microwaves (VMs). Vacuum was used to control the boiling point of water and to maintain temperature in the bacterial suspensions at specified levels (49–64°C).z-Value in the water bath treatment was 9·1°C while for VM at 510 and 711 W it was 6·2 and 5·9°C, suggesting thatE. coliis more sensitive to temperature changes under microwave heating. Arrhenius calculations of the activation energies of the destruction reactions suggest that the mechanism of destruction in VM may be different from that of conventional heat. The number of injured micro-organisms showed no significant differences among treatments.The impact of temperature onE. colidestruction was different when microwaves were the medium of heat transfer, suggesting the existence of factors other than heat contributing to the lethal effect of VM. [ABSTRACT FROM AUTHOR]

c. iversen, m. lane and s.j. forsythe. 2004. To study the growth, thermotolerance and biofilm formation of the emergent pathogen Enterobacter sakazakii in infant formula milk (IFM). The temperature range, death kinetics and biofilm formation of E. sakazakii were determined using impedance microbiology and conventional methods. In IFM the organism grew as low as 6°C and optimally at 37–43°C. In faecal coliform tests, 23% of strains ( n = 70) produced gas from lauryl sulphate broth (LSB) at 44°C after 48 h incubation. Three strains failed to grow in LSB at any of the temperatures. The D-value of cells suspended in IFM was determined between 54 and 62°C. The resultant z-value was 5·7°C. The organism was able to adhere and grow on latex, polycarbonate, silicon and to a lesser extent stainless steel. Enterobacter sakazakii was able to grow at refrigeration temperatures and on infant-feeding equipment. The thermotolerance of the organism was similar to other Enterobacteriaceae and should be killed during standard pasteurization treatment. Enterobacter sakazakii has been associated with infant meningitis through consumption of contaminated IFM. Enterobacter sakazakii is able to grow in IFM during storage at refrigeration temperatures and attach to infant-feeding equipment, which may become reservoirs of infection. [ABSTRACT FROM AUTHOR]

Thermal inactivation kinetics with extrapolation were used to model the survival probabilities of spores of various Bacillus species over time periods of millions of years at the historical ambient temperatures (25–40 °) encountered within the 250 million-year-old Salado formation, from which the putative ancient spore-forming bacterium Salibacillus marismortui strain 2-9-3 was recovered. The model indicated extremely low-to-moderate survivalprobabilities for spores of mesophiles, but surprisingly high survival probabilities for thermophilic spores. The significance of the results are discussed in terms of the survival probabilities of (i) terrestrial spores in ancient geologic samples and (ii) spores transported betweenplanets within impact ejecta. [ABSTRACT FROM AUTHOR]

Tahini (sesame paste) is a traditional food. Numerous foodborne outbreaks have been associated with it. This study aimed to (i) explore the efficiency of 2450 MHz microwave heating at 220, 330, 440, 550, and 660 W on the inactivation of Salmonella spp, Escherichia coli O157:H7, and Listeria monocytogenes in tahini; (ii) determine the impact of desiccation and starvation stresses on pathogen survival; (iii) assess the impact of microwave heating on the physicochemical characteristics of tahini. The inoculated microorganisms in tahini were reduced with higher microwave power levels (p < 0.05) and longer exposure times. The D-values of unstressed Salmonella spp., Escherichia coli O157:H7, and L. monocytogenes ranged from 6.18 to 0.50 min, 6.08 to 0.50 min, and 4.69 to 0.48 min, respectively, at power levels of 220 to 660 W, with z-values of 410, 440, and 460 W, respectively. Generally, desiccation and starvation stress levels prior to heating increased microbial resistance to heat treatment. Microwave heating did not affect acid, peroxide, p-anisidine, or color values of tahini up to 90 °C. These findings reveal microwave heating as a potential method for lowering the risk of Salmonella spp., E. coli O157:H7 and L. monocytogenes in tahini with no compromise on quality. [ABSTRACT FROM AUTHOR]

Animal intestines are the source of edible sausage casings, which are traded worldwide and may come from areas where notifiable infectious animal diseases are prevalent. To estimate the risks of virus contamination, knowledge about the quantity of virus and decimal reduction values of the standard preservation method by salting is of great importance. A literature search, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was performed in search engine CAB Abstracts to determine the viral load of 14 relevant animal viruses in natural casings or intestines. Only a very limited number of scientific publications per virus were found and viral loads in the intestines varied from high for ASFV (five publications), BVDV (3), CSFV (6), PPRV (3), RPV (2) and TGEV (3) to moderate for PEDV (2) and SVDV (3), low for HEV (2) and FMDV (5), very low for VESV (1) and negative for PrV (2) and VSV (1). PRRSV was found in intestines, however, viral titers were not published. Three viruses (BVDV, CSFV and PPRV) with high viral loads were selected to search for their inactivation kinetics. For casings, no inactivation data were found, however, thermal inactivation data of these viruses were available, but differed in quantity, quality and matrices. In conclusion, important data gaps still exist when it comes to the quantitative inactivation of viruses in sausage casings or livestock intestines. [ABSTRACT FROM AUTHOR]