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The objective of the present study was to compare the thermal inactivation and sublethal injury kinetics of Salmonella enterica and Listeria monocytogenes in broth (suspended cells) and on solid surface (agar-seeded cells). A 3-strain cocktail of S. enterica or L. monocytogenes inoculated in broth or on agar was subjected to heating in a water bath at various set temperatures (55.0, 57.5 and 60.0°C for S. enterica and 60.0, 62.5 and 65°C for L. monocytogenes). The occurrence of sublethally injured cells was determined by comparing enumerations on nonselective (TSAYE) and selective (XLD or ALOA) media. Results showed that the inactivation curves obtained from selective media were log-linear, and significant shoulders (p

This chapter addresses the need for the aseptic operation of fermentation processes and the procedures adopted to achieve it—the sterilization of the process plant, the medium and air supply. The kinetics and scale-up of medium sterilization by wet heat are discussed in terms of specific death rate (k), Del factor (▿), and nutrient quality criterion (Q) as well as in terms of decimal reduction time (D), Z value, F0 value, and R0 value. The design and operation of batch and continuous medium sterilization systems are compared as means of sterilizing fermentation media, feeds, and liquid wastes. The theory of fixed pore and nonfixed pore filtration is addressed and their application to the sterilization of heat-labile solutions is discussed as well as the methods used to size such filters. Finally, the sterilization of both fermenter inlet and exhaust air is discussed.

Heating processes are paramount means for preventing food-borne illnesses. For conventional heating, time and temperature recommendations are given to improve food safety. These recommendations are based on two key-parameters: D- and z-values. With the aim of saving time and energy, microwave technologies are particularly interesting for cooking or decontaminating foods. However, the D- and z-values are not appropriate for such treatments because the heating temperature is not constant. New parameters based on the specific power are proposed to characterize this heating process (Dp- and zp-values). In this chapter, microwave heating and its impacts on microorganisms are described. An outline on thermobacteriology in food processing is reported, followed by a presentation of the methodology used for determining the Dp- and zp-values. Finally, the application of Dp- and zp-values for sterilization, pasteurization, and cooking operations using microwave technology is presented.

Summary This study was conducted to investigate the effects of cold oxygen plasma (COP) on the reductions of Penicillium citrinum and Cladosporium cladosporioides on the surface of dried filefish fillets (Stephanolepis cirrhifer). The counts were significantly (P 0.05) differences were observed in the counts between 3 and 5 min of COP. The average decrease in the counts of C. cladosporioides and P. citrinum caused by 3–20 min of COP was 0.91 and 1.04 log10 CFU g � 1 , respectively. A reduction of >1-log10 CFU g � 1 was observed on the fillets treated with COP for >10 min. Decimal reduction time (dR) by Weibull model was 9.32 and 7.42 min of COP for C. cladosporioides and P. citrinum, respectively. The fillets exposed to 20 min of COP displayed increased thiobarbituric acid reactive substance (TBARS) and decreased overall sensory acceptance. However, the fillets treated with 10 min of COP received satisfactory TBARS and consumer acceptance. Therefore, a 10-min COP could be effective in reducing >90% and inactivating of the mould without causing any deleterious changes to the physicochemical and sensory qualities of the fillet.

The purpose of this work was to compare inactivation of spores from the heat resistant Bacillus cereus strain F4430/73 by high pressure treatment at elevated temperature (HPHT) versus thermal treatment (HT). Spore suspensions were treated at 0.1 and 600 MPa at 60–100 °C for different times. HT inactivation could be described by a first-order kinetic model, while HPHT inactivation showed a fast followed by a slow phase. Significant spore inactivation occurred during pressure come-up and equilibration time (2.0 to 4.1 log10, from 70 to 100 °C). HPHT inactivation proceeded considerably faster than HT inactivation, even in the slow phase which also followed first-order kinetics (e.g. D100 °C(600 MPa) = 1.7 min, D100 °C = 3.4 min). The D values at 0.1 and 600 MPa also showed a distinct temperature dependency, with z values of 10.6 and 21.2 °C, respectively. The data indicate a strong synergistic effect of HP and HT on inactivation of B. cereus spores. Industrial relevance HPHT processing is an emerging technology for the production of shelf-stable and safe foods with a higher quality than conventional thermal appertization. Quantitative data on the inactivation of bacterial pathogens, in particular from sporeformers, is essential to demonstrate that the process is indeed safe and efficient, and to develop a methodological framework for process calculation and validation. The current work is one of the first to provide such data on the inactivation of B. cereus, which is among the most important sporeformers in terms of food spoilage and safety.

Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and Salmonella spp. can survive the spray-drying process if milk is contaminated after pasteurization, and the dried product can be contaminated from environmental sources. Compared with conventional heating, radio-frequency dielectric heating (RFDH) is a faster and more uniform process for heating low-moisture foods. The objective of this study was to design an RFDH process to achieve target destruction (log reductions) of C. sakazakii and Salmonella spp. The thermal destruction (decimal reduction time; D-value) of C. sakazakii and Salmonella spp. in NDM (high-heat, HH; and low-heat, LH) was determined at 75, 80, 85, or 90 °C using a thermal-death-time (TDT) disk method, and the z-values (the temperature increase required to obtain a decimal reduction of the D-value) were calculated. Time and temperature requirements to achieve specific destruction of the pathogens were calculated from the thermal destruction parameters, and the efficacy of the RFDH process was validated by heating NDM using RFDH to achieve the target temperatures and holding the product in a convection oven for the required period. Linear regression was used to determine the D-values and z-values. The D-values of C. sakazakii in HH- and LH-NDM were 24.86 and 23.0 min at 75 °C, 13.75 and 7.52 min at 80 °C, 8.0 and 6.03 min at 85 °C, and 5.57 and 5.37 min at 90 °C, respectively. The D-values of Salmonella spp. in HH- and LH-NDM were 23.02 and 24.94 min at 75 °C, 10.45 and 12.54 min at 80 °C, 8.63 and 8.68 min at 85 °C, and 5.82 and 4.55 min at 90 °C, respectively. The predicted and observed destruction of C. sakazakii and Salmonella spp. were in agreement, indicating that the behavior of the organisms was similar regardless of the heating system (conventional vs. RFDH). Radio-frequency dielectric heating can be used as a faster and more uniform heating method for NDM to achieve target temperatures for a postprocess lethality treatment of NDM before packaging.

Gradual exposure to moderate acidic environments may enhance the thermal tolerance and survival of Escherichia coli O157:H7 in acid and acidified foods. Limited studies comparing methodologies to induce this phenomenon have been performed. The effects of strain and physiological state on thermal tolerance and survival of E. coli in apple juice were studied. The decimal reduction time (D-value) at 56°C [D56°C] was determined for E. coli O157:H7 strains C7927 and ATCC 43895 and E. coli O111 at four physiological states: unadapted, acid-shocked (two methodologies used), and acid-adapted cells. The effect of acidulant was also evaluated by determining the D56°C for the O157:H7 strains subjected to acid shock during 18 h in Trypticase soy broth (TSB), with pH 5 adjusted with hydrochloric, lactic, and malic acids. Survival of the three strains at four physiological states was determined at 1 ± 1°C and 24 ± 2°C. Experiments were performed in triplicate. For thermal inactivation, a significant interaction was found between strain and physiological state (P0.0001). Highest thermal tolerance was observed for the 43895 strain subjected to acid shock during 18 h in TSB acidified with HCl (D56°C of 3.0 ± 0.1 min) and the lowest for the acid-shocked C7927 strain treated for 4 h in TSB acidified with HCl (D56°C of 0.45 ± 0.06 min). Acidulants did not alter the heat tolerance of strain C7927 (D56°C of 1.9 ± 0.1 min; P0.05) but significantly affected strain 43895 (P0.05), showing the greatest tolerance when malic acid was used (D56°C of 3.7 ± 0.3 min). A significant interaction between strain, storage temperature, and physiological state was noted during the survival experiments (P0.05). E. coli O111 was the most resistant strain, surviving 6 and 23 days at 24 and 1°C, respectively. Our findings may assist in designing challenge studies for juices and other pH-controlled products, where Shiga toxin-producing E. coli represents the pathogen of concern.

The thermal inactivation kinetics of spores from 39 Bacillus cereus strains belonging to six different phylogenetic groups (group II to VII) was studied. Fresh spore suspensions in glass capillaries were heated in an oil bath at three or more different temperatures for five different times. Survival curves and thermal death curves were established and the kinetic parameters DT (decimal reduction time at temperature T) and z (temperature dependence of DT) were derived by linear regression. Most strains (38/39) had survival curves without a pronounced shoulder or tail, as reflected by linear regression coefficients R2 generally higher than 0.95. The heat resistance of the strains and groups of strains was then compared by determining the temperature (°C) at which logD = 0.8 (TlogD = 0.8). Spores from group VI strains showed significantly lower heat resistance than all other groups except group II, with TlogD = 0.8 ranging between 82.7 °C and 92.8 °C. Spores from groups III and VII, on the other hand, were generally most heat resistant, with TlogD = 0.8 between 91.9 °C and 101.8 °C. Further analysis revealed a positive correlation between spore heat resistance and both minimal and maximal growth temperatures of the strains. In contrast, the z value was negatively correlated with the minimal and maximal growth temperatures. The availability of genetic group-specific heat resistance data will contribute to a more accurate risk assessment of B. cereus.

The aim of this research was to analyze and model the combined effect of pressure and temperature upon Aspergillus ochraceus spores exposed to high pressure carbon dioxide (HPCD) treatment and to estimate the kinetic parameters. Lately, many empirical or semi-empirical mathematical models were presented and discussed for different microorganisms, mainly bacteria, demonstrating an increased need for tools able to quantify the parameters of the microbial inactivation. A. ocharaceus HPCD inactivation was adequately described by first order reaction kinetics and a synergic effect of pressure and temperature was noticed for the experimental range where pressure varied from 5.4 to 7.0 MPa and temperature varied from 30 to 50 °C. The decimal reduction time ( D ) ranged from 47.07 min at 5.4 MPa and 30 °C to 5.04 min at 7.0 MPa and 50 °C. In this study three mathematical models were evaluated in order to find the best one that describes accurately the influence of pressure and temperature on the studied microbial response. An empirical exponential equation, that described pressure and temperature influence in the form of a polynomial equation, was found to best describe the dependence of A. ochraceus HPCD inactivation in the range 5.4–7.0 MPa and 30–50 °C. This work adds insight to moulds inactivation at the already existing body of knowledge on bacteria inactivation with HPCD and provides support to potential industrial applications of the minimal–thermal methods that combine high pressure and mild temperature with carbon dioxide for different food matrixes.

This study was performed to evaluate the sporicidal efficacy of a fumigation disinfectant containing 20% ortho-phenylphenol against Clostridium perfringens (C. perfringens) spores. In this research, efficacy test of fumigant against C. perfringens spores was carried out according to French standard NF T 72-281. C. perfringens spores working culture suspension number (N value), all the spore numbers on the carriers exposed with the fumigant (n1, n2, and n3), the number of bacterial spore suspensions by pour plate method (N1), the number of bacterial spore suspensions by filter membrane method (N2) and the mean number of bacterial spore recovered on the control-carriers (T value) were obtained from the preliminary test. In addition, the reduction number of C. perfringens spores exposed with the fumigant (d value) was calculated using T value, the mean number of bacterial spore in recovery solution (n'1) and the mean number of bacterial spore on carriers plated in agar (n'2). N value was 4.3 × 10 7 spores/mL, and n1, n2, and n3 were higher than 0.5N1, 0.5N2 and 0.5N1, respectively. Additionally, T value was 4.9 × 10 5 spores/carrier. In the sporicidal effect of the fumigant, the d value was 4.52log reduction. According to the French standard for the fumigant, the d value for the effective sporicidal fumigant should be over than 3log reduction. The results indicated that Fumagari OPP ® had an efficient sporicidal activity against spores of C. perfringens, then the fumigant can be

Modeling inactivation of indicator microorganisms is a necessary component of microbial water quality forecast and management recommendations. The linear semi-logarithmic (LSL) model is commonly used to simulate the dependencies of bacterial concentrations in waters on time. There were indications that assumption of the semi-logarithmic linearity may not be accurate enough in waters. The objective of this work was to compare performance of the LSL and the two-parametric Weibull inactivation models with data on survival of indicator organism Escherichia coli in various types of water from a representative database of 167 laboratory experiments. The Weibull model was preferred in >99% of all cases when the root mean squared errors and Nash–Sutcliffe statistics were compared. Comparison of corrected Akaike statistic values gave the preference to the Weibull model in only 35% of cases. This was caused by (i) a small number of experimental points on some inactivation curves, (ii) closeness of the shape parameter of the Weibull equation to one, and (iii) piecewise log–linear inactivation dynamic that could be well described by neither of the two models compared. Based on the Akaike test, the Weibull model was favored in agricultural, lake, and pristine waters, whereas the LSL model was preferred for groundwater, wastewater, rivers, and marine waters. The decimal reduction time parameter of both the LSL and Weibull models exhibited an Arrhenius-type dependence on temperature. Overall, the existing E. coli inactivation data indicate that the application of the Weibull model can improve the predictive capabilities of microbial water quality modeling.

The individual and combined effects of high pressure carbon dioxide (HPCD) and nisin (200 IU/mL) on the inactivation of Escherichia coli O157:H7 suspended in physiological saline (PS, pH 5.60), phosphate-buffered saline (PBS, pH 5.60 or 7.00) or carrot juice (pH 6.80) were evaluated. The pressure in this study was 5 and 8 MPa, the temperature was 25 °C–45 °C, and the treatment time was 5–65 min. Inactivation of cells in PS (pH 5.60) by HPCD followed first order kinetics, the k (the inactivation rates) increased while the D (decimal reduction time) decreased in the presence of nisin, however, the acid solution dissolving nisin rather than nisin itself played a prominent role in this combination effect with HPCD in PS buffer. The inactivation kinetics of cells in PBS (pH 5.60 or 7.00) and carrot juice (pH 6.80) by HPCD followed slow-to-fast two-stage kinetics and was fitted by the modified Gompertz equation. The M (the time at which the absolute death rate is maximum) significantly decreased in the presence of nisin. HPCD enhanced the sensitization of E. coli to nisin and the time for the complete inactivation was shortened by 2.5–5 min in PBS buffer and carrot juice by combination of HPCD and nisin (HPCD + nisin) than by HPCD alone. Regression coefficients (R2) and mean square error (MSE) were used to evaluate the model performance, indicating that the models could provide a good fitting to the experimental data.

Objectives: This study evaluated the fungicidal efficacy of a fumigant containing 20% ortho-phenylphenol against Trichophytone mentagrophytes (T. mentagrophytes), Candida albicans (C. albicans) and Aspergillus niger (A. niger). Methods: Five replicates of each carrier were contaminated by depositing 0.05 mL of each fungal suspension. After drying, two carriers without exposure to the fumigant and three carriers with exposure to the fumigant were left in a sealed room (25 ㎥) at 21±0.5℃ and 60±10% relative humidity for 15 hours. Immediately after removal from the test room, each carrier was transferred into recovery diluent and suspended, diluted and inoculated. After incubation, the numbers of each colony were counted, and the parameter values (N, T, d) were calculated. Results: The working culture suspension number (N value) of T. mentagrophytes, C. albicans and A. niger were 1.0×10?, 1.2×10? and 5.7×10? CFU/mL, respectively. All the colony numbers on the carriers exposed to the fumigant (n1, n2, n3) were higher than 0.5N1 (the number of fungal test suspensions by pour plate method), 0.5N2 (the number of fungal test suspensions by filter membrane method) and 0.5N1, respectively. In addition, all mean numbers of test strains recovered on the control-carriers (T value) were over 10? CFU/mL. For the fungicidal effect of the fumigant, all numbers of fungal reductions after exposure of the fumigant (d value) were 4 ?CFU/mL. Conclusions: The present study showed that fumigant containing 20% ortho-phenylphenol has effective fungicidal activity against T. mentagrophytes, C. albicans and A. niger.

This study established the inactivation behavior of Listeria monocytogenes in nonfat, low-fat and full-cream milks treated with multifrequency Dynashock ultrasound. Inactivation in all samples was biphasic, with an inactivation lag phase where injury accumulated, prior to log-linear inactivation phase. L. monocytogenes exhibited shortest lag phase of 20.57 min in full-cream milk. L. monocytogenes exhibited slowest log-linear inactivation rate of −0.24 log colony-forming unit (cfu)/min in full-cream milk, and fastest inactivation rate of −0.37 log cfu/min in low-fat milk. Inactivation rate was slowest in full-cream milk at −0.24 log cfu/min, and fastest in low-fat milk at −0.37 log cfu/min. Corrected decimal reduction time was shortest in full-cream milk at 24.81 min, followed by those in nonfat and low-fat milk at 29.17 and 30.64 min, respectively. These results suggest the importance of careful consideration of microbial inactivation behavior in the establishment of food process schedules. Practical Applications The results reported in this study may be considered in the application of multifrequency power ultrasound-based processing of milk products against the tested reference microorganisms. Ultrasound processing may also be used in combination with other physical and/or chemical preservation methods to achieve a recommended level of lethality for safety and quality of the products.

By means of the establishment of thermal stability evaluation model and simulating in Huafeng factory residential building ,the relationship between the D value and building thermal stability and the optimal distribution ratio are obtained.The results show that:at the shape coefficient≤0.40, the most optimal matching relation is :heat transfer coefficient is 1.0, thermal inertia index is 2.0;at the shape coefficient >0.40, the most optimal matching relation is :heat transfer coefficient is 0.8, thermal inertia index is 2.0.

Controlling phosphate (P) release from agricultural soils to water while maintaining optimal plant growth conditions remain a major challenge for the development of sustainable agricultural systems. To achieve this, it is important to have a proper knowledge of the amount of soil P that can be mobilized by water and of the kinetics of P release. We evaluated the ability of a flow-through reactor in which 33 P labeled soils can be inserted and leached continuously with deionized water, to assess P release. The experiment was conducted on five grassland soils presenting a large range in P availability. The availability of P in these soils was further modified by submitting them to 0 to 3 plant growth cycles with Italian ryegrass ( Lolium multiflorum ) with three levels of P added (0, 20 and 40 mg P kg soil −1 ). The P input–output balance, water and oxalate extractable P, the degree of P saturation of the soil and the amount of isotopically exchangeable P ( E value) were assessed in all samples. A subset of these soil samples was labeled with 33 P, introduced in a flow-through reactor and the release of P and 33 P measured over 14 days. The cumulated amount of P released after 14 days was strongly correlated to the amount of oxalate extractable P, isotopically exchangeable P ( E value), and water extractable P. The P release kinetics was modeled with a 2 pools model with each pool following first order kinetics. Plants were able to take up P from both pools. Assuming that the leached P had the same isotopic composition as the pool of soil P it came from it became possible to quantify the amount of isotopically exchangeable remaining in the soil which was called the D value. D decreased during the three first days of the flow-through experiment and then increased linearly with time reaching a maximum after 14 days. This maximum remained lower than the oxalate extractable P. Processes contributing to this increase were isotopic exchange and possibly also some organic P mineralization. The D value was strongly linearly correlated to E values measured after different exchange times, but for a given exchange time, the D value was lower than the E value, whereas equality could have been expected. This difference was related to the high rate of 33 P export from the soil at the beginning of the flow-through experiment. The D value was also strongly correlated to the oxalate and water extractable P. In conclusion, we suggest that the use of the flow-through reactor yields relevant information on the amount of P that can be leached from a given soil, and that the D value delivers information on the amount of isotopically exchangeable P remaining in the soil and therefore which could still be leached if sufficient time would be given.

The effects of high pressure processing, (HPP) applied within 100 to 600 MPa for 1 s to 20 min at ambient temperature (30 ± 2 °C), on the color, biochemical characteristics and inactivation kinetics of natural microflora in fresh mango pulp ( Mangifera indica cv. Amrapali) were investigated. Changes in color of mango pulp were found to be significant after HPP. Processed pulp retained a maximum of 85, 92 and 90% of its original ascorbic acid, total phenolics and in-vitro antioxidant capacity, respectively. Isobaric destruction of microorganisms followed the first-order death kinetics. Among the groups of microorganisms studied, pressure sensitivity of coliforms was found to be maximum whereas yeast & mold were least sensitive ( z P values of 306.8 and 630.5 MPa; ΔV values of − 18.9 × 10 − 6 and − 9.2 × 10 − 6 m 3 mol − 1 , respectively). High pressure treatment of 600 MPa for 5 min was adjudged best for mango pulp which achieved maximum reduction in microflora and moderate changes in quality attributes. Industrial relevance Mango is the king of fruits which is globally valued for its unique aroma, flavor and high nutritive value. Most of the current preservation techniques available for mango involve the use of thermal treatments which result in loss of quality. India ranks no.1 in global mango production and has huge potential for utilizing new preservation technologies, such as HPP, which promise fresh-like and shelf stable products. This study will help one to understand the changes induced by HPP in mango pulp which may further be applied to develop the process technology for preservation of mango based products.

This test was performed to evaluate the bactericidal efficacy of a fumigation disinfectant containing 20% ortho-phenylphenol against Pseudomonas aeruginosa (P. aeruginosa) and Enterococcus hirae (E. hirae). In preliminary tests, P. aeruginosa and E. hirae working culture suspension number (N value) were 2.8 × 10 and 4.0 × 10 CFU/mL, respectively. And all the colony numbers on the carriers exposed to the fumigant (n1, n2, n3) were higher than 0.5N1 (the number of bacterial test suspentions by pour plate method), 0.5N2 (the number of bacterial test suspentions by filter membrane method) and 0.5N1, respectively. In addition, the mean number of P. aeruginosa and E. hirae recovered on the control-carriers (T value) was 2.8 × 10 and 3.4 × 10 CFU/mL, respectively. In the bactericidal effect of the fumigant, the reduction number of 2.8 × 10 (d value) was 6.46 and 5.19 logCFU/mL, respectively. According to the French standard for the fumigant, the d value for the effective bactericidal fumigant should be over than 5 logCFU/mL. With the results from this study, the fumigation disinfectant containing 20% ortho-phenylphenol has an effective bactericidal activity, then the fumigant can be applied to disinfect food materials and kitchen appliances contaminated with the pathogenic bacteria.

The use of raw milk in the processing of buffalo Mozzarella cheese is permitted, but the heat treatment used for stretching the curd must ensure that the final product does not contain pathogens such as Shiga toxin-producing Escherichia coli (STEC) that may be present on buffalo dairy farms. This study carried out challenge tests at temperatures between 68 °C and 80 °C for 2 to 10 min to simulate curd temperatures during the stretching phase. Curd samples were inoculated with 2 STEC strains (serotypes O157 and O26), and their inactivation rates were assessed in the different challenge tests. The curd samples were digested with papain to ensure a homogeneous dispersion of bacteria. The STEC cells were counted after inoculation (range 7.1-8.7 log cfu/g) and after heat treatments using the most probable number (MPN) technique. A plot of log MPN/g versus time was created for each separate experiment. The log linear model with tail was used to provide a reasonable fit to observed data. Maximum inactivation rate (k(max), min(-1)), residual population (log MPN/g), decimal reduction time (min), and time for a 4D (4-log10) reduction (min) were estimated at each temperature tested. A 4D reduction of the O26 STEC strain was achieved when curd was heated at 68 °C for 2.6 to 6.3 min or at 80 °C for 2.1 to 2.3 min. Greater resistance was observed for the O157 strain at 68 °C because k(max) was 1.48 min(-1). The model estimates can support cheesemakers in defining appropriate process criteria needed to control possible STEC contamination in raw milk intended for the production of Mozzarella.

For the production of trans-resveratrol-amplified grape juice, both trans-resveratrol quantity and microbial quality are important for the functionality and shelf life of the juice. Therefore, the thermal stability of trans-resveratrol and thermal inactivation of Saccharomyces cerevisiae within the grape juice was investigated at 60?C, 80?C and 100?C. Inactivation of S. cerevisiae was fitted to first-order kinetics, and the inactivation rate (k1) and decimal reduction time (D-value) at each treatment temperature were estimated. The control grape juice had an inactivation rate of 0.0014 (s-1) and a D-value of 11.90 min at 60?C, whereas the trans-resveratrol-amplified grape juice had an inactivation rate of 0.0016 (s-1) and a Dvalue of 10.42 min at the same temperature. Similar inactivation kinetics of the control and trans-resveratrol-amplified grape juice were observed at 80?C and 100?C, which indicates that increased trans-resveratrol content does not affect the thermal inactivation of inoculated S. cerevisiae.

Protective solid carriers are commonly added to probiotic cultures prior to drying. Their formulation is not trivial and depends on the drying conditions applied. In this study, we systematically investigated the influence of formulation parameters on the survival of Lactobacillus plantarum WCFS1 after drying. Low molecular weight carbohydrates (less than 2 kDa) with high glass transition temperatures provided the highest level of protection at both low (25 degrees C) and high (50 degrees C or higher) drying temperatures. Low molecular weight carbohydrates may provide stabilization by closely interacting with the lipid bilayer of the cell membranes. Meanwhile, carbohydrates with high glass transition temperatures probably provide stabilization via fixation of the cells in a glassy powder. Furthermore, adequate amounts of solid carrier are required to sufficiently stabilize the cells during drying. During drying, crystallization of solid carriers may occur. Depending on the crystal geometry, crystallization can be either beneficial (e.g. with mannitol or sorbitol) or detrimental (e.g. with lactose) to cell survival. Finally, the effect of formulation on cell viability during storage was studied. A decimal reduction time of approximately 300 days was observed when spray dried L. plantarum WCFS1 was stored at temperatures below 40 degrees C. The outcome of this study was used as a basis to construct a generalized diagram to indicate the combinations of formulation and drying conditions to maximally retain viability and operate dryers at high efficiency. (C) 2013 Elsevier Ltd. All rights reserved.

β-galactosidase from Lactobacillus leichmannii 313 (LL313) was purified (4.5-fold, 11% purification yield), and characterised, giving optimal enzyme activity at pH 5.5 and 55 °C. Thermal inactivation of crude and purified enzyme showed first order inactivation kinetics. Deactivation energy (Ed) of 390.58 ± 34.94 kJ/mol (crude enzyme) and 404.17 ± 46.19 kJ/mol (purified enzyme), based on the Arrhenius equation were not significantly different. Thermal stability, determined by decimal reduction time (D value), z value, and half-life (t1/2) of purified enzyme were significantly lower than those of crude enzyme. This, together with thermodynamic parameters (ΔH#, ΔG# and ΔS#) suggested that the purification procedure affected the thermal stability of the enzyme. The purified enzyme gave Vmax and Km values of 9.15 ± 0.23 mol g−1.min−1 and 2.97 ± 0.32 mM respectively, with ο-nitrophenol-β- d -galactopyranoside as substrate. The purified enzyme was activated by Na+ ions (>1 mM); remained unaffected by K+; and was inhibited by Ca2+ and Mn2+ (1–100 mM). Inhibition by EDTA (1 mM) and activation by 2-mercaptoethanol (1 mM) demonstrated respectively that the enzyme is a metalloenzyme and required cysteine in the active site. The enzyme exhibited hydrolytic and transgalactosylation activities with lactose as substrate, demonstrating its potential for use in the food industry.

In the present study, the synergistic disinfection efficacy of low concentration electrolyzed water (LcEW) (free available chlorine, 4 mg/L) combined with brief heat enhancement was evaluated and the bactericidal mechanism was investigated by atomic force microscopy (AFM). The inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium on organic carrot were fitted with Weibull model to evaluate the synergistic effects. LcEW is effective at inactivating E. coli O157:H7 and S . Typhimurium on organic carrots, and the efficacy is dependent on the temperature. The combined treatment with LcEW at 80 °C resulted in decimal reduction time ( T R ) of 7.42 and 3.27 s for E. coli O157:H7 and S. Typhimurium, respectively. The reactive oxygen species generated from LcEW were responsible for the microbial inactivation. In addition, AFM observation of E. coli O157:H7 and S. Typhimurium revealed morphological alterations in the bacterial cell structure, which illustrated the damage of cell membrane injury and intracellular component leakage. Quality attributes of carrot treated with LcEW and short-time heating (70 °C, 1 min) were not significantly different from controls. Compared to the control group, the combined treatment exhibited significantly ( P

Restaurants used to prepare tenderloin beef medallions using different frying parameters in order to satisfy their customers. However, some of those cooking methods are not in accordance with food safety recommendations, because they do not reach internal temperatures recognized as save, in countries such as US, Canada and Brazil. This study aimed to assess the microbial inactivation in tenderloin beef medallions fried to five pre-determined degrees of doneness. Two different frying techniques were investigated, allowing beef pieces to reach the following degrees of doneness: rare, medium-rare, medium, medium-well and well-done. Before thermal processing, tenderloin beef medallions were artificially contaminated with approximately 106 CFU/g of Escherichia coli and the survival of this microorganism and mesophilic total counts were measured using VRBA + MUG and BHI plates, respectively. Bacterial colonies grew on BHI plates were also analyzed by Matrix-Assisted Laser and Time-Of-Flight desorption/ionization mass spectrometry (MALDI-TOF/MS) in order to identify survivors. Results indicated that complete E. coli inactivation was only observed on tenderloin beefs subjected to well-done degree established by both techniques, given that Technique 1 recommended a final heating inside oven after frying. Without this final oven processing, which is not always done in restaurants, more than 2 log CFU/g of viable E. coli were detected. Modeling of the kinetic parameters by GInaFIT revealed a D value (time needed to reduce 90% of the bacterial population) of 1.67 min for Technique 1 and D = 3.81 min for Technique 2 and this difference was associated to the difference of temperatures of olive oil. MALDI-TOF analyses demonstrated high diversity in natural microbiota of tenderloin beef pieces and among the main identified survivor genera was Citrobacter, Enterobacter, Hafnia, Serratia, Raoultella, Bacillus, Lactobacillus, Micrococcus, Pseudomonas, Serratia and Staphylococcus. Pathogens such as Salmonella and Listeria monocytogenes were not found. Based on the results, we recommend the use of high microbiological quality beef for the preparation of tenderloin beef medallions and the validation of frying process considering specific conditions of restaurants, because different degrees of fried may result in different counts and types of bacterial survivors.

Egg shell (ES) was a good inducer for caseinase enzyme production by Bacillus megaterium 314 without adding supplements (only distilled water). Mixture of ES with molokihya stalk (MS) was the most suitable substrate that increased enzyme production by 4.7-fold. Optimized HCl pretreatment of ES using Central composite design enhanced enzyme production by 3.3-fold. Moreover, caseinase production was enhanced by 2.5-fold using Plackett-Burman (PB) followed by Central composite (CC) design. Enzyme showed maximum activity at temperature 50 °C and pH 9.0. Activation energy (Ea) and activation energy for the thermal denaturation (Ed) were 11.2 and 135.9 kJ/mol, respectively. Caseinase was highly tolerant to heat inactivation retained 93.6% of its initial activity after 1 h heating at 50 °C. In addition, the calculated half-life time (t0.5) and decimal reduction time (D-value) at 50 °C were 26.9 and 89.3 h, respectively. Moreover, thermodynamic parameters (enthalpy, Gibbs free energy and entropy) indicated that the enzyme was highly tolerant to heat inactivation. Sesame protein was the most suitable for hydrolysis by caseinase. Optimization of Sesame proteolysis using CC design causing 16.9-fold increases compared with the unoptimized. In vitro results showed promising biological activities as anticoagulation and fibrinolytic for caseinase preparation.

The objective of this study was to measure the inactivation efficiencies of intense pulsed light (IPL) on six types of bacteria and determine how the efficiency values are related to the spectral transmittance of IPL. All of the microorganisms exhibited up to 7-log CFU/mL reductions, and the double-Weibull survival model provided the best fit to the inactivation curves. We obtained 4Dv values (which is the fluence required to inactivate 99.99% of viable cells) and zv values (which is the increase in lamp voltage required for a 1-log reduction of the 4Dv value) for lamp voltages ranging from 800 to 1800 V (corresponding to total fluences from 0.00 to 11.41 J/cm2). The 4Dv values for Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Enteritidis, and Shigella sonnei for IPL treatment at 1800 V were 1.57, 0.66, 0.62, 0.79, 0.66, and 1.63 J/cm2, respectively, while the corresponding zv values were 5553, 3590, 3201, 3678, 3672, and 6440 V, respectively. The variations in the sensitivity to IPL were related to differences in the transmittance of the microorganisms. A practical model was developed to predict the 4Dv values of microorganisms based on their transmittance and the IPL lamp voltage.

This study was performed to evaluate the bactericidal efficacy of Fumagari OPP ® , fumigation dis- infectant, containing 20% ortho-phenylphenol against Staphylococcus aureus (S. aureus). In this research, efficacy test of fumigant against S. aureus was carried out according to French standard NF T 72-281. S. aureus working cul- ture suspension number (N value), all of the colony numbers on the carriers exposed with the fumigant (n1, n2, and n3), the number of bacterial test suspentions by pour plate method (N1), the number of bacterial test suspentions by filter membrane method (N2) and the mean number of bacteria recovered on the control-carriers (T value) were obtained from the preliminary test. In addition, the reduction number of S. aureus exposed with the fumigant (d value) was calculated using T value, the mean number of bacteria in recovery solution (n'1) and the mean number of bacteria on carriers plated in agar (n'2). N value was 4.0 × 10 8 CFU/mL, and n1, n2, and n3 were higher than 0.5N1, 0.5N2 and 0.5N1, respectively. Additionally, T value was 3.4 × 10 6 CFU/mL. In the bactericidal effect of the fumigant, the d value was 6.43 logCFU/mL. According to the French standard for the fumigant, the d value for the effective bacteri- cidal fumigant should be over than 5 logCFU/mL. The results indicated that Fumagari OPP ® had an effective bacteri- cidal activity against S. aureus, then the fumigant can be applied to disinfect food materials and kitchen appliances contaminated with pathogenic bacteria.

Summary The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC-CO2). Addition of ethanol to the SC-CO2 at 2% (v/v) caused greater inactivation than SC-CO2 alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first-order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC-CO2 remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.

High-pressure (HP) inactivation of pure avidin as well as avidin in egg were evaluated and compared with conventional thermal inactivation kinetics. Test samples were treated at 500 to 700 MPa and 80 to100C for pure avidin and at 500 to 700 MPa and 30 to 50C for avidin present in egg white and whole liquid egg. Avidin inactivation was well described by the first-order kinetic model. Pure avidin was found to be relatively very resistant as compared with avidin in egg, and thermal inactivation was much slower than HP inactivation. Conventional thermal treatment at 100C gave a D value of 111 min while HP treatment (700 MPa) at the same temperature reduced the D value to 26 min for pure avidin. However, avidin naturally present in egg was sensitive to both thermal and pressure treatments. Avidin in egg had a D100C value of 10.0 to 10.9 min indicating greater heat sensitivity. Conventional thermal treatment at 50C had negligible effect on avidin inactivation in egg while HP treatment at 700 MPa almost completely inactivated it in 5–10 min (D value of 2.2 min). The pressure and temperature sensitivity parameters (z value) were also determined both as a function of pressure at different temperatures and as a function of temperature at different pressure levels. Practical Applications Avidin present in egg white possesses antinutritional properties as it can bind with biotin (vitamin B7) making it inaccessible to the body. Biotin is an important vitamin necessary for cell growth, metabolism of fats and amino acids in the human body. It has been shown that one molecule of avidin has the ability to bind four molecules of biotin. Since avidin is very stable, processing treatments aim at inactivating it so as to make biotin available for digestion and absorption by the body. Avidin is traditionally inactivated by thermal processing. HP processing is a nonthermal alternative to conventional thermal processing aimed at minimizing the thermal damage to quality factors. This research compares thermal and HP techniques for inactivating avidin. HP has been shown to accelerate the inactivation of avidin.

This test was performed to evaluate the bactericidal efficacy of Fumagari OPP, fumigation disinfectant, containing 20% ortho-phenylphenol against Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium). In preliminary tests, both E. coli and S. typhimurium working culture suspension number (N value) was CFU/mL. And all of the colony numbers on the carriers exposed the fumigant (n1, n2, n3) were higher than 0.5N1 (the number of bacterial test suspentions by pour plate method), 0.5N2 (the number of bacterial test suspentions by filter membrane method) and 0.5N1, respectively. In addition, the mean number of bacteria recovered on the control-carriers (T value) was CFU/mL. In the bactericidal effect of the fumigant, the reduction number of S. typhimurium and E. coli (d value) was 5.26 and 5.64 logCFU/mL, respectively. According to the French standard for the fumigant, the d value for the effective bactericidal fumigant should be over than 5 logCFU/mL. With the results of this study, Fumagari OPP has an effective bactericidal activity, then the fumigant can be applied to disinfect food materials and kitchen appliances contaminated with pathogenic bacteria.

Nitrogen utilization efficiency (NUE) was a hot topic in the study area of crop cultivation, most scholars tented to calculate NUE by D-value method, which could well reflected the total absorption of N nutrient by crops; and on the other hand, the tracing technique could precisely calculated the N content which crops absorbed from N fertilizer. In this study, the flue-cured tobaccos were treated with 2 N levels and 3 water levels, and the D-value method and the tracing method was adopted to calculate the nitrogen utilization efficiency. Results showed that the RD value was more than double the RN value, and there were no relationships between the results calculated by the D-value method and the tracing method, the treatment with higher RN value could not always obtain a higher RD value; besides, water deficiency or excess could both decreased NUE, through affecting the N availability or through the elution of the N nutrient. Taken as the whole, 6g/plant N combined with 800mm irrigation water was more beneficial for the effective utilization of N fertilization, and which combined with 1000mm was more beneficial for the N accumulation of tobacco plants.

Time–temperature integrators (TTIs) based on inactivation of a-amylase (BAA70) was used for validation of obtained pasteurization values in fish burgers on a complex frying line with two frying units and a hot air tunnel. The target was a pasteurization value of P70 7.5 = 2, representing 6 log reduction of Listeria monocytogenes. The TTI was calibrated and had a decimal reduction time D70C of 27.2 min and z value of 6.5C. The temperature was measured with thermocouples at different steps in the process and used for validation of a multiphysics computation model. The temperature profile calculated from the model was combined with known inactivation kinetics and the residual a-amylase activity was calculated and compared with actual values of the TTIs placed in the core of the burgers. Our results showed that a-amylase BAA70 can be used as a biochemical TTI to validate a specific minimum pasteurization value for fried fish burgers.

Due to the growing numbers of infection outbreaks in hospitals, it is essential to set up an effective sanitation program. The kinetic parameter of killing time (D-value) was experimentally determined to study the effectiveness of some chemical agents used in hospitals. A total of 115 Air-borne bacteria were isolated from 12 wards of a hospital in Alexandria, Egypt. They were tested for their resistance to different antibiotics and commercial disinfecting agents. Three isolates were selected, identified and their D-values were determined against seven chemical agents (hydrogen peroxide, chlorine, betadine, phenik, iodine, dettol, and savlon). The bacterial strains were Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis representing the Gram positive,Gram negative and spore former, respectively. The results revealed that P. aeruginosawas the most sensitive organism where B. subtilis and S. aureus showed approximately same resistance pattern. The data of this study reflect the importance of selecting the appropriate chemical agent to be used for killing specific microorganisms in appropriate time. In conclusion, successful disinfection depends upon the selection of the correct chemical agent associated with a proper disinfecting procedure. Key words: Chemical agents, disinfection, D-value, hospitals, air borne bacteria.

This paper presents a study of the effect of the low temperature atmospheric helium dielectric barrier discharge (DBD) on the Streptococcus mutans biofilms formed on tooth surface. Pig jaws were also treated by plasma to detect if there is any harmful effect on the gingiva. The plasma was characterized by using optical emission spectroscopy. Experimental data indicated that the discharge is very effective in deactivating Streptococcus mutans biofilms. It can destroy them with an average decimal reduction time (D-time) of 19 s and about 98% of them were killed after a treatment time of 30 s. According to the survival curve kinetic an overall 32 s treatment time would be necessary to perform a complete sterilization. The experimental results presented in this study indicated that the helium dielectric barrier discharge, in plan-parallel electrode configuration, could be a very effective tool for deactivation of oral bacteria and might be a promising technique in various dental clinical applications.

Patulin is a mycotoxin produced by a wide range of molds involved in fruit spoilage, most commonly by Penicillium expansum and is a health concern for both consumers and manufacturers. The current study evaluated feasibility of monochromatic ultraviolet (UV) radiation at 253.7 nm as a possible commercial application for the reduction of patulin in fresh apple cider and juice. The R-52G MINERALIGHT® UV bench top lamp was used for patulin destruction. It was shown that 56.5%, 87.5%, 94.8% and 98.6% reduction of patulin can be achieved, respectively, in the model solution, apple cider, apple juice without ascorbic acid addition and apple juice with ascorbic acid addition in 2-mm thickness sample initially spiked by 1 mg·L−1 of patulin after UV exposure for 40 min at UV irradiance of 3.00 mW·cm−2. A mathematic model to compare the degradation rate and effective UV dose was developed. The effective UV doses that were directly absorbed by patulin for photochemical reaction were 430, 674, 724 and 763 mJ·cm−3, respectively. The fluence-based decimal reduction time was estimated to 309.3, 31.3, 28.9 and 5.1 mW·cm−2·min, respectively, in four media mentioned above. The degradation of patulin followed the first-order reaction model. The time-based and fluence-based reaction rate constants were determined to predict patulin degradation. The time-based reaction rate constant of samples treated in dynamic regime with constant stirring (model solution: 2.95E-4 s−1, juice: 4.31E-4 s−1) were significantly higher than samples treated in static regime (model solution: 2.79E-4 s−1, juice: 3.49E-4 s−1, p