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Water activity (a w ) of ground beef, chicken breast meat, and trout fillets was modified to intermediate (a w 0.98-0.99) and lowest (a w 0.94-0.96) levels. The meat samples with modified and unaltered (native, a w 1.00) a w were inoculated with Escherichia coli O157:H7 and subjected to electron beam (e-beam). Survivor curves were plotted and the D 10 -values were calculated. The D 10 -values ranged from 0.22 kGy for trout at native a w to 0.33 kGy for beef at intermediate, and chicken and trout at lowest a w . Regardless of the species, a w reduction increased E. coli resistance to e-beam, suggesting that even small depletion of unbound water from food increases survival. The difference of the D 10 -values between the samples at intermediate and lowest a w was insignificant. E-beam could be used before a w -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 a w .

The objective of this study was to compare the inactivation effects of ohmic heating (internal heating by electric current) and conventional heating (external heating by hot water) on viable aerobes and Streptococcus thermophilus 2646 in milk under identical temperature history conditions. The effects of the two treatments on quality of milk were also compared by assessing degrees of protein denaturation in raw milk and sterilized milk (raw milk being sterilized by ohmic heating or conventional heating). It was found that microbial counts and calculated decimal reduction time (D value) resulting from ohmic heating were significantly lower than those resulting from conventional heating. There was no difference in degrees of protein denaturation during the two treatments. The results suggested that ohmic heating had not only a lethal thermal effect but also a lethal nonthermal effect due to the electric current on microorganisms. Based on the results, we propose that ohmic heating can be effectively used to pasteurize milk with no additional protein deterioration.

A thermal-death-time (TDT) disk was designed to evaluate microbiological inactivation kinetics by heat. A first order inactivation kinetic model is described by the D value and the z value. These kinetic data are critical in the design, operation and regulation of thermal pasteurization. D and z values of Salmonella enteritidis strain 13076 and Escherichia coli K12 in liquid whole egg and liquid egg white were determined over the temperature range from 52 to 60 °C. In liquid whole egg, D 54 , D 56 , D 58 and D 60 values of S. enteritidis strain 13076 were 5.70, 0.82, 0.27 and 0.17 min, respectively, and D 54 , D 56 , D 58 and D 60 values of E. coli K12 were 9.10, 1.41, 0.67 and 0.22 min, respectively. In liquid egg white, D 52 , D 54 , D 56 and D 58 values of S. enteritidis strain 13076 were 6.12, 1.51, 0.42 and 0.19 min, respectively, and D 52 , D 54 , D 56 and D 58 values of E. coli K12 were 10.18, 1.82, 0.78 and 0.28 min, respectively. The z values for S. enteritidis strain 13076 and E. coli K12 ranged from 3.95 to 4.03 °C. The results showed that D values of S. enteritidis strain 13076 and E. coli K12 in liquid whole egg were higher than those in liquid egg white. E. coli K12 exhibited similar kinetic behavior, but higher thermal resistance than S. enteritidis strain 13076 in both liquid egg white and liquid whole egg. This study demonstrated that non-pathogenic E. coli K12 may serve as a surrogate for pathogenic S. enteritidis in liquid egg in the validation of a thermal pasteurization.

The effects of heavy metals Cd2+, Pb2+ and Zn2+ at 0.05, 0.5 and 5.0 mg/L level and their interactions at 0.5 mg/L level on DNA damage in hepatopancreas of loach Misgurnus anguillicaudatus for 1–35 days exposure were examined by single cell gel electrophoresis (SCGE). For each test group, 20 loaches with similar body size (5.17–7.99 g; 11.79–13.21 cm) were selected and kept in aquaria with dechlorinated water at (22±1)°C and fed a commercial diet every 48 h. According to the percentage of damaged DNA with tail and its TL/D (tail length to diameter of nucleus) value, the relationship between DNA damage degree and heavy metal dose and exposure time was determined. Results showed that the percentage of damaged DNA and the TL/D value were increased with the prolonged exposure time. The highest percentage (84.85%) of damaged DNA was shown in 5.0 mg/L Zn2+ group after 28 days exposure and the biggest TL/D value (2.50) in all treated groups after 35 days exposure. During the first treated week, the damnification of DNA was mainly recognized as the first level, after that time, the third damaged level was mostly observed and the percentage of damaged DNA was beyond 80%. The joint toxic effects among Cd2+, Pb2+ or Zn2+ revealed much complexity, but it generally displayed that the presence of Cd2+ could enhance the genotoxicity of Pb2+ or Zn2+. In conclusion, the results suggested that there was a significant time-and dose-depended relationship between the heavy metal and DNA damage in hepatopancreas of loach, and SCGE could represent a useful means to evaluate the genotoxicity of environmental contamination on aquatic organisms.

The inactivation of peroxidase (POD) and polyphenol oxidase (PPO) in red beet extract with high pressure carbon dioxide (HPCD) was investigated. HPCD treatment at 37.5 MPa for POD and 22.5 MPa for PPO (55 °C, 60 min) resulted in a reduction of their activities by approximately 86% and 95%, respectively. Compared with thermal treatment (55 °C), the decimal reduction time ( D ) of POD and PPO was reduced from 555.56 min to 74.63 min and 161.29 min to 38.31 min, respectively, by the HPCD treatment. The inactivation process followed first-order kinetics ( R 2 > 0.84, p D values declining with the rise of pressure and temperature. The activation energy of the inactivation was reduced by the HPCD treatment from 92.54 kJ/mol to 68.63 kJ/mol and 57.06 kJ/mol to 53.58 kJ/mol for POD and PPO, respectively. Analysis of the kinetic parameters of the inactivation showed that both POD and PPO were less sensitive to pressure changes under supercritical than subcritical conditions. Industrial relevance There is a strong interest in the food industry in developing non-thermal processing techniques to produce fresher, safer and higher quality food. High pressure carbon dioxide (HPCD) is one of the emerging non-thermal technologies for inactivating microorganisms and enzymes in food products. Peroxidase (POD) and polyphenol oxidase (PPO) are two common enzymes that can cause quality deterioration in many food products. This work explores the feasibility of inactivating POD and PPO in red beet extracts by HPCD and establishes the inactivation kinetic models. These models are useful in understanding the responses of POD and PPO activities to changes in the HPCD parameters including pressure, temperature and process time. The models may also be used in assisting the design of industrial-scale HPCD processes.

In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 degrees C) to 0.7 min (100 degrees C) in apple juice, 14.1 (90 degrees C) to 1.0 min (100 degrees C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 degrees C) to 1.2 min (100 degrees C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 degrees C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.

Alicyclobacillus acidoterrestris is a thermoacidophilic, non-pathogenic, spore-forming bacterium detected in spoiled commercial pasteurized fruit juice. Apple, white grape and tomato are particularly susceptible. A. acidoterrestris spores are resistant to lemon juice pasteurization (2 min at 82°C), and they can germinate and grow causing spoilage. This contamination is characterized by a medicinal or disinfectant smell attributed to guaiacol (o-dihydroxybenzene) production and other taint chemicals. The aim of this work was to study the influence of temperature (82, 86, 92 and 95 °C), total soluble solids (SS) (6.20, 9.8, 50 and 68°Brix) and pH (2.28, 2.45, 2.80, 3.25, 3.5) on decimal reduction time (D) of the A. acidoterrestris in clarified and non-clarified concentrated lemon juice. Once D-value was determined, the resistance of A. acidoterrestris at the assayed temperatures was confirmed. SS and pH influence spore viability, because spore resistance increases with higher SS (50°Brix 22 min 82 °C–68°Brix 28 min 82 °C) and pH values (pH 2.28, 17 min–pH 4.00, 22 min). Bacterial growth was lower in clarified lemon juice, 26 min at 82 °C, than in non-clarified lemon juice, 51 min at 82 °C. Temperature was the parameter that had the greatest influence on the D value. Fil: Belfiore, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Biotecnología; Argentina Fil: Maldonado, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Biotecnología; Argentina Fil: Navarro, Antonio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Biotecnología; Argentina

Intense light pulse (ILP) is one of the emerging non-thermal techniques investigated as an alternative to traditional thermal treatment because it has been proven to be effective for microbial inactivation on food surfaces and food packages. The aim of this study was to evaluate the possibility of using pulsed light treatment for the effective killing of moulds on paper–polyethylene packaging material. Coupons of 20 × 20 mm paper–polyethylene were artificially contaminated with Cladosporium herbarum , Aspergillus niger , Aspergillus repens and Aspergillus cinnamomeus than subjected to different light energetic densities (from 0.244 to 0.977 J/cm 2 ) for different durations (from 10 × 10 −3 to 30 × 10 −3 s). The results showed that there is a significant reduction of population along with an increase of light fluence and ILP treatment duration. The highest level of inactivation achieved in this study was about a 2.7-log reduction, which is more than enough for a normal contaminated packaging material. It is estimated that pulse light treatment could lead to an effective reduction of moulds, being also possible to obtain a sterile surface of the packaging material. Blastospores as those produced by C. herbarum are easier destroyed ( z = 0.795 J/cm 2 ) than fialospores as those produced by aspergilli ( z = 0.81–0.927 J/cm 2 ). Spore colour seems to play some role in spore resistance to light pulses: green fialospores, as those produced by A. repens , has higher z values (0.927 J/cm 2 ) than the black or brown ones as those produced by A. niger ( z = 0.81 J/cm 2 ), and A. cinnamomeus ( z = 0.875 J/cm 2 ) respectively.

Batch and dynamic extractions of uranium(VI) in 10−3–10−2M concentrations in 3–4M nitric acid medium have been investigated using a commercially available phosphinic acid resin (Tulsion CH-96). The extraction of uranium(VI) has been studied as a function of time, batch factor (V/m), concentrations of nitric acid and uranium(VI) ion. Dual extraction mechanism unique to phosphinic acid resin has been established for the extraction of uranium(VI). Distribution coefficient (K d ) of uranium(VI) initially decreases with increasing concentration of nitric acid, reaches a minimum value at 1.3M, followed by increases in K d . A maximum K d value of ∼2000 ml/g was obtained at 5.0M nitric acid. Batch extraction data has been fitted into the linearized Langmuir adsorption isotherm. The performance of the resin under dynamic extraction conditions was assessed by following the breakthrough behavior of the system. Effect of flow rate, concentrations of nitric acid and uranium ion in the feed on the breakthrough behavior of the system was studied and the data was fitted using Thomas model.

A crude acetone extract of the pit of date palm (Phoenix dactyliferaL.) was prepared and its antiviral activity evaluated against lyticPseudomonasphage ATCC 14209-B1, usingPseudomonas aeruginosaATCC 25668 as the host cell. The antiviral activity of date pits was found to be mediated by binding to the phage, with minimum inhibitory concentration (MIC) of −1. The decimal reduction time (D-values), the concentration exponent (η) and the phage inactivation kinetics were determined. The date pit extracts show a strong ability to inhibit the infectivity ofPseudomonasphage ATCC 14209-B1 and completely prevented bacterial lysis, which it is hoped will promote research into its potential as a novel antiviral agent against pathogenic human viruses.

Anthocyanin content in Sicilian sweet orange [ Citrus sinensis (L) Osbeck] varieties known as blood oranges ( Tarocco , Moro e Sanguinello ) undergoes changes during the ripening process. Concentration increases during ripening, reaching a maximum in the fully ripe fruit. At latter stage of maturity, a decrease of these pigments is observed. This study aims to evaluate β- d -glucosidase activity (βG, EC 3.2.1.21) in Tarocco variety, the most common Sicilian blood orange, and to determine the main physicochemical and kinetic properties of this enzyme in order to underline its role on anthocyanins degradation during ripening. The enzymatic extract was assayed on both anthocyanins extract from Tarocco juice and a synthetic substrate ( p -nitrophenyl-β- d -glucopyranoside, p NPG). It was observed a 400 times higher specificity of the synthetic substrate than the natural substrate. Kinetic studies and physicochemical characterization of βG such as V max and K m ( V max 2.1 × 10 −2 and K m 2.67 × 10 −4 using p NPG as substrate; V max 3.3 × 10 −3 and K m 2.1 × 10 −1 using natural substrate), optimum conditions of pH (4.5) and temperature (60 °C), fructose and glucose inhibition (competitive inhibition by glucose) and thermal stability (decimal reduction time 3 min at 75 °C and decimal reduction temperature 9.5 °C) were also performed. β- d -Glucosidase activity seems involved on anthocyanins degradation during final ripening stage of fruit.

Wine is a complex solution containing several components with several likely antimicrobial properties. Low pH (3.0 to 4.0), high organic acid content (titratable acidity > or = 6.0 g/L tartaric acid), relatively high ethanol (10% to 15%), and potentially high total sulfur dioxide (0 to 300 ppm) may contribute to inactivation of food-borne pathogens when exposed to wine. The objective was to determine the effect of these 4 parameters on reducing populations of Escherichia coli (E. coli) O157:H7 and Staphylococcus aureus. A factorial design was used to test variables (pH, titratable acidity, sulfur dioxide, ethanol) in combinations of low, medium, and high levels. Suspension tests were performed to compare the efficacy of 81 treatments with controlled exposure time of 20 min. Staphylococcus aureus was significantly more resistant to wine treatment than E. coli O157:H7. Stepwise regression analysis of S. aureus inactivation revealed the ordered impact of pH, molecular sulfur dioxide, titratable acidity, and ethanol concentration. Selected analysis of E. coli inactivation revealed the importance of pH and ethanol in predicting inactivation. Total and free sulfur dioxide were not predictive of inactivation of either pathogen. Wine-based solutions may have application as surface disinfectants for food surfaces and food contact equipment. Wine destined to be used as a disinfectant could be enhanced by increasing any of the parameters tested in this study; however, lowering the pH would be the most effective and would likely enhance the efficacy of the other parameters. Additional wine components such as volatile acidity and phenolics were not evaluated but may also contribute to the antimicrobial properties of wine.

This study established the thermal inactivation of Salmonella Typhimurium (E1366) in a mixture of golden apple snail ( Pomacea conaliculata Linn.) meat and coconut cream medium—a dish native to the Philippines locally known as guinataang kuhol. Artificially inoculated S. Typhimurium were heated to 60, 75 and 90 °C for 0–1.5 min. Survivor cells were enumerated using a selective and a nonselective enumerating medium, bismuth sulphite agar (BSA) and nutrient agar (NA), respectively. The thermal inactivation rates of Salmonella Typhimurium were expressed in terms of decimal reduction times ( D -values). Results showed that in both enumerating media and in all heating temperatures, the number of surviving cells significantly ( P D -values calculated from the survivor counts on both media were however not significantly different. The calculated D -values ranged from 0.22 to 0.48 min.

The thermal resistance of Bacillus stearothermophilus spores at different stages of rehydration was examined. Inoculation was achieved by rehydrating pasta samples in water containing 1-mL spore crop (10 6 spores/mL); the product was heat sealed in sterile pouches and processed in a laboratory retort. Thermal inactivation of spores was carried out using 10 time intervals at 121C for moisture contents, 70, 90, 105, 115, 125 and 145% dry basis. The death curves obtained consisted of two phases, an initial rapid decline (1.5 to 2.6 log reductions) followed by a slower, linear decrease of survivors from which the decimal reduction time (D value) was calculated. D 121 values were found to decrease with increasing moisture content and ranged from 4.6 to 6.5 min. The thermal resistance constant (z value) was examined to assess the effect of temperature (110-125C) on lethality, z values decreased with increasing moisture content and ranged from 10.7 to 15.6C. The results of this study demonstrate that temperature and moisture content influence the effectiveness of the intended heat process. For products that are rehydrated during heat treatment, the moisture content of the product is a critical factor. Therefore, if complete rehydration is not achieved, this may result in the heat process being less effective for the destruction of microorganisms, which may have implications in regard to food safety.

Summary The errors in calculations of blanching time and enzyme inactivation (decimal reduction time) when one common value of thermal diffusivity is adopted for all vegetables are considered. Different rates of heat transfer (negligible heat transfer resistance and blanching in water by natural convection), food size, decimal reduction time of the enzyme (D), and reciprocal slope of the log D vs. temperature curve (parameter z), were analysed. These variables influenced the blanching time more than the thermal diffusivity and consequently, for many industrial situations, a single thermal diffusivity value of 1.5 x 10-7m2s-1 could be used without causing significant errors in blanching calculations.

Summary 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.

Summary The resistance to solutions of hydrogen peroxide of dry spores of Bacillus subtilis var. globigii (NCIB 8058) was studied between concentrations of 10 and 30% (w/v) at temperatures from 20 to 50°C. Logarithmic relationships were obtained between decimal reduction time and temperature at different concentrations of hydrogen peroxide. The difference between the resistance of wet and dry spores to hydrogen peroxide is discussed.

The values for thermal inactivation of pectinesterase in mandarin orange juice were F197.5 = 1.00 (Z = 194) and D197.5 = 0.54 min (Z = 20.6) at pH 3.6, and F201.5 = 1.00 (Z = 17) and D201.5 = 0.438 min (Z = 18.2) at pH 4.0. The F values were equivalent to 1.85 D at pH 3.6 and 2.28 D at pH 4.0. F is the thermal inactivation time (min) at a given temp. ( degree F), D is the decimal reduction time and Z is the number of degree F required for the inactivation or reduction time temp. curve to traverse one log cycle. A 2 D process at pH 3.6 and 2.5 D process at pH 4.0 are recommended in the commercial pasteurization of juice. A viscosity procedure described is more sensitive than the jelly test for determining the thermal inactivation of pectinesterase.

A global logistic model incorporating a dummy variable for the growth medium (laboratory media or table olives brine) was used for the estimation of the growth-no growth interface of Issatchenkia occidentalis as a function of NaCl, citric and sorbic acid concentrations. The model permitted the deduction of the region where the combination of citric and sorbic acids in laboratory media (above 0.3% and 0.03% wt/vol, respectively) and brine (above 0.1% and 0.03% wt/vol), at 5% NaCl, inhibited the growth of the yeast. Subsequently, the model was validated in laboratory media within the no growth region by a response surface D-optimal design. Inactivation concentrations of sorbic acid produced a progressive loss of viability in I. occidentalis that followed a first order kinetic or downward concave inactivation curves, depending on environmental variables. These curves were properly described by a (primary) model deduced from the Weibull distribution, whose parameters, first decimal reduction time (D(beta)) and shape (beta), were expressed as a function of sorbic acid concentrations (secondary model). At 5% NaCl and within the experimental region checked, an increase of 0.010% and 0.008% sorbic acid reduced D(beta) in 10 h and decrease beta by 10%. Finally, the model was also validated in real "seasoned" table olives packing reporting a complete inactivation of the yeasts' population.

It is possible to describe the pressure degradation of microorganisms as being analogous to thermal inactivation. Equation for baroinactivation is derived from thermal death time (TDT) model D p = D pref 10(pref-p)/z p , where D pref is decimal reduction time at the reference pressure (min), p ref is the reference pressure (MPa), z p is the pressure increase (MPa) required to reduce the D p value by a factor of 10. This method was used for the calculation of baroinactivation model parameters of the total number of microorganisms of pressurized germinated mung bean (green gram) seeds (Vigna radiata (L.) Wilczek). Microbial contamination of germinated mung bean (green gram) seeds can be effectively decreased by treatment at a high pressure of 400 MPa, time of pressurization 5 min.

A candidate Time–Temperature Integrator (TTI) which is potentially suitable for use in validation of sterilisation processes was identified and tested. The TTI was based on the highly thermostable amylase produced from the extracellular medium of a Pyrococcus furiosus fermentation: this organism grows at temperatures in the region of 100 °C. Kinetic properties for the amylase following inactivation by heat showed it to be suitable for use as a sterilisation TTI. Isothermal kinetic data at 121 °C and non-isothermal kinetic data over the range 121 to 131 °C were determined. A decimal reduction time ( D T -value) at 121 °C of 24 min was calculated from isothermal tests and a range from 18.1 to 23.9 min from non-isothermal tests. A z -value of 10 °C was estimated from non-isothermal tests. Thus, sterilisation values ( F 0 ) estimated from this TTI would be similar to F 0 -values representative of the destruction of Clostridium botulinum spores. Industrial measurements under non-isothermal conditions were conducted in metal cans processed in an FMC reel and spiral cooker–cooler and a bar simulator, and also in plastic pouches processed in a Lagarde steam-air retort. Industrial relevance Many food processes, such as canning, are based upon thermal sterilisation of the food material. The development of a reliable Time–Temperature Integrator for such a process would be industrially valuable by providing a simple way of validating such processes. This study demonstrates the feasibility of one such TTI.

This paper reports the covalent immobilization of penicillin G acylase from E. coli on Sepabeads EC-EP, an epoxy-activated polymethacrylic carrier, and describes the properties of the immobilized enzyme. Due to its versatility to mediate hydrolysis of penicillins and semi-synthetic B-lactam antibiotics synthesis reactions, the selected enzyme belongs to a class of biocatalysts of great industrial interest. The immobilized enzyme was characterized in its pH and thermal stability and reaction kinetics. The immobilization of penicillin acylase resulted in a slightly different pH activity profile and temperature optima, indicating that the immobilization by this method imparted the structural and conformational stability to this enzyme. The immobilized enzyme also retained a high catalytic activity and showed the increased thermal stability compared with a free enzyme. By comparison of decimal reduction time values obtained at 50?C, it can be concluded that the immobilized enzyme was approximately 5-fold more stable than a free enzyme. The immobilization procedure developed is quite simple and easily reproduced, and provides a promising solution for the application of penicillin acylase for the purpose of 6-aminopenicillanic acid production.

The inactivation kinetics of lactic acid bacteria, Lactobacillus fructivorans, which is responsible for the deterioration of sake (Japanese rice wine) quality, was investigated using a continuous flow system for high-pressure carbonation. In addition, the effects of ethanol and sugar concentration on lactic acid bacteria inactivation were investigated. Cells of L. fructivorans (1×106CFU/ml) were inactivated at a treatment temperature of 40°C and a pressure of 20MPa, with a residence time of 1.7min. The D-values (decimal reduction time) at 30 and 35°C were 4.3 and 0.6min, respectively. In addition to ethanol, glucose in sake also increased the inactivation efficiency of L. fructivorans by the carbonation treatment. These results suggest that the present technique is an effective microbial inactivation method for alcoholic beverages such as sake.

We previously developed a method for evaluating the heat resistance of microorganisms by measuring the transition temperature at which the coefficient of linear expansion of a cell changes. Here, we performed heat resistance measurements using a scanning probe microscope with a nano thermal analysis system. The microorganisms studied included six strains of the genus Bacillus or related genera, one strain each of the thermophilic obligate anaerobic bacterial genera Thermoanaerobacter and Moorella, two strains of heat-resistant mold, two strains of non-sporulating bacteria, and one strain of yeast. Both vegetative cells and spores were evaluated. The transition temperature at which the coefficient of linear expansion due to heating changed from a positive value to a negative value correlated strongly with the heat resistance of the microorganism as estimated from the D value. The microorganisms with greater heat resistance exhibited higher transition temperatures. There was also a strong negative correlation between the coefficient of linear expansion and heat resistance in bacteria and yeast, such that microorganisms with greater heat resistance showed lower coefficients of linear expansion. These findings suggest that our method could be useful for evaluating the heat resistance of microorganisms.

peer-reviewed The presence of Salmonella in animal feed or feed ingredients at the feed mill or on-farm is a cause for concern, as it can be transmitted to food-producing animals and subsequently to humans. The objective of this study was to determine the survival characteristics of five feed ingredient- and feed-derived monophasic Salmonella Typhimurium 4,[5],12:i:- strains. The first part of the study investigated thermal inactivation using an immersed heating coil apparatus. A Weibull model provided a good fit, with low RMSE values (0.04–0.43) and high R2 values (0.93–0.99) obtained. There was considerable inter-strain variation in heat resistance, with D-values ranging from 397.83 to 689 s at 55 °C, 11.35–260.95 s at 60 °C and 1.12 to 6.81 at 65 °C. Likewise, z-values ranged from 2.95 to 5.44 °C. One strain demonstrated a significantly higher thermal tolerance, even though it had been isolated from a meal feed. However, overall the strains investigated do not appear to be that much more heat resistant than Salmonella previously studied. The second part of this study involved assessing the ability of the five Salmonella strains to survive during storage over a 28-day period in pelleted weaner pig feed treated with 0.3% sodium butyrate. While a mean reduction in the Salmonella count of 0.79 log10 CFU was seen in the treated feed during the storage period, a reduction (albeit only 0.49 log10 CFU) was also observed in the control feed. Although there was no overall effect of treatment, sodium butyrate resulted in reductions in Salmonella counts of 0.75 and 0.22 log10 CFU at days 14 and 24 of feed storage, respectively but at the end of the 28-day storage period counts were 0.25 log10 CFU higher in the treated feed. Therefore, the sodium butyrate used appears unsuitable as an agent for feed treatment perhaps due to the protective coating on the particular feed additive used. Overall, the results of this study enhance knowledge about the behaviour and survival characteristics of monophasic S. Typhimurium 4,[5],12:i:- strains in animal feed and may assist the feed industry and pig producers in implementing effective intervention strategies for their control. Teagasc Walsh Fellowship Programme (Ref: 2011010)

Soil amended with manure has been implicated as a source of produce contamination leading to foodborne gastrointestinal-disease outbreaks. While current composting guidelines require temperatures ≥ 55°C for 3 days to destroy bacterial pathogens, these requirements have not been evaluated for all pathogens. Investigation of parasite survival in manure required development of a flow cytometry method integrating the cell-impermeant viability dye SytoX for simultaneous quantification and viability assessment of Cryptosporidium and Giardia oocysts/cysts. Further studies will be required to apply this method to investigate thermal reduction in parasites. Studies conducted with bacterial pathogens indicated that E. coli O157:H7 survived longer than other pathogens at 50°C to 55°C. Listeria monocytogenes survived significantly better in chicken manure compared to cow manure at 50°C to 55°C. Results suggest composting guidelines are adequate for bacterial pathogen reduction; however, testing for E. coli O157 along with Salmonella may increase confidence in compost safety.

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.

A model for the process impact temperature non-uniformity during high pressure processing (HPP) of genipap fruit purees was found during genipin recovery. Purees were subjected to HPP (130-530 MPa) under quasi-isobaric non-isothermal conditions (15 min; 0, 4.6 and 9.3mg pectinases/g fruit). Genipin and protein concentration was determined, and pH was measured. Polygalacturonase activity was quantified indirectly by protein content (mg/g fruit). First order kinetics described temperature changes (0-4 min). Polygalacturonase was activated at 130 MPa, inactivated reversibly at 330 MPa and activated again at 530 MPa. Enzyme reaction rate constant (k) was placed in the 0-4 min model and temperature from 2 to 15 min was described. Protein content and pH characterization in terms of decimal reduction time improved highly the 2-15 min model. Since temperature changes were modeled, more insight of its behavior in an HPP reactor was obtained, avoiding uniformity assumptions, making easier the industrial scale HPP implementation.

Even when using vegetative cells, a tailing phenomenon can be observed in survivor curves in engineering researcher’s papers on gas plasma sterilization. This indicates that even disinfection was not even achieved. By definition, sterilization is a process that kills all types of microorganisms including bacterial spores and vegetative cells. In contrast, disinfection kills only vegetative cells and does not kill bacterial spores. Tailing of a survivor curve is often caused by clumping of the biological indicator (BI), and engineering researchers who make their own BI without critical knowledge, appropriate techniques and confidential know-how to avoid such clumping frequently publish nonlinear survivor curves. Preparation of a monolayer of BI is quite a difficult task even for BI manufacturers and it requires proprietary information. Therefore, engineering researchers should purchase commercially available BI. Among the BIs on the market, I recommend purchasing BI from Merck Co., as clumping was found to be minimal based on results of scanning electron microscopy (SEM) observation. When such a tailing phenomenon is observed, a SAL of 10-6 cannot be attained, and therefore no D value (decimal reduction value) can be determined and the exposure time for a 9 or 12 log reduction remains undefined. The D value must be determined from the straight line of a 9 log or 12 log reduction survivor curve, and there can only be one D value per microorganism; there is never more than one D value per one microorganism. The BI is defined as the most tolerant microorganism (typically bacterial spores) to the sterilization procedure being used, so if the BI is killed, then other contaminants (microorganisms) can be speculated to also be killed. Therefore, the use of a BI is essential in sterilization validation studies and routine control. Strategies to avoid clumping, tailing phenomena and to attain a SAL of 10-6 will be considered in this article.

In order to determine the causes of sweetened adzuki ann spoilage, the characteristics of microorganism isolated from spoiled adzuki ann were investigated. The isolated microorganism was gram-positive, rod-shaped and spore-forming bacteria; its surface was smooth and glazed. From the results of the assimilation test of 46 different biochemicals by the Vitec 2 Compact test and comparison of the cellular wall composition of fatty acid by the data bank of Midi sherlock system, the microorganism was identified as Bacillus subtilis. D-value of the B. subtilis spore was 4.85 min at 115℃, 0.69 min at 121℃ and 0.48 min at 125℃; Z-value was 9.71. The Bacillus subtilis growth was not observed below water activity of 0.92 at 45℃. However, bacteria growth increased gradually as water activity increased above 0.93.

Thermal tolerance of acid-adapted Escherichia coli O157:H7 or Salmonella in ground beef was evaluated during storage at 4 degrees C or -20 degrees C. Both pathogens were adapted to acidic conditions (pH approximately 4.6) by growing in tryptic soy broth supplemented with 1% glucose. A five-strain cocktail of E. coli O157:H7 or Salmonella was grown separately in TSB (pH approximately 6.6) and TSB + 1% glucose for 24 h at 37 degrees C to provide cells with or without acid adaptation. Irradiated ground beef was inoculated with either acid-adapted or non-adapted E. coli O157:H7 or Salmonella; the samples stored at 4 degrees C were subjected to heat treatment at 62 degrees C or 65 degrees C on days 1, 7, 14, 21, and 28, and the samples stored at -20 degrees C were subjected to heat treatment at 62 degrees C or 65 degrees C on days 1, 30, 60, 90, and 120. Decimal reduction time (D values) of the pathogens was determined as an indicator of thermal tolerance. Significantly higher D(62) values were observed on days 21 and 28 for non-adapted E. coli O157:H7 stored at 4 degrees C and on days 90 and 120 for non-adapted E. coli O157:H7 stored at -20 degrees C (P0.05). Higher D(62) values were observed on days 21 and 28 among non-adapted Salmonella strains stored at 4 degrees C and on day 28 for acid-adapted strains of Salmonella stored at 4 degrees C (P0.05). Higher D(62) values for acid-adapted strains of Salmonella stored at -20 degrees C were observed on days 30, 60, and 90 (P0.05), when while no differences were observed in the D(65) values of acid-adapted and non-adapted strains of E. coli O157:H7 and Salmonella throughout storage at both temperatures (P0.05). This suggests that acid adaptation of foodborne pathogens provides a certain level of protection against heat treatment at lower cooking temperatures, while at higher temperatures there were no observed differences between the sensitivity of acid-adapted and non-adapted strains in an actual food system over an extended period of refrigerated and frozen storage.

Aim: To determine the survival of Escherichia coli O157:H7 in dairy wastewater from on-site holding lagoons equipped with or without circulating aerators. Methods and Results: Survival was monitored in dairy lagoon microcosms equipped with or without scale-size circulators. Both laboratory strains of E. coli O157:H7 and an isolate of E. coli H7 from wastewater had poor survival rates and none proliferated in water from waste lagoons with or without circulators. Furthermore, the decline of E. coli O157:H7 was not enhanced in those microcosms equipped with circulators. Strain variation in survival was observed in both circulated and settling waters. The decline rate of E. coli O157:H7 Odwalla strain increased proportionately with the inoculum load. Escherichia coli failed to establish itself in wastewater even after four sequential inoculations simulating continuous faecal input into the lagoon. The native aerobic bacteria survived longer with a decimal reduction time of 21·3 days vs either introduced or native E. coli, which declined rapidly with decimal reduction time of 0·5–9·4 days. Conclusions: Escherichia coli O157:H7 failed to establish and proliferate in dairy wastewater microcosms equipped with or without circulating aerators. Significance and Impact of the study: This study furthers our knowledge of pathogen survival in wastewater, and suggests that proper management of wastewater before its use in irrigation is essential to reduce pathogen transfer to crops.

Using artificial neural networks (ANNs), a highly accurate model was developed to simulate survival curves of Listeria monocytogenes in chorizos as affected by the initial water activity (a(w0)) of the sausage formulation, temperature (T), and air inflow velocity (F) where the sausages are stored. The ANN-based survival model (R(2)=0.970) outperformed the regression-based cubic model (R(2)=0.851), and as such was used to derive other models (using regression) that allow prediction of the times needed to drop count by 1, 2, 3, and 4 logs (i.e., nD-values, n=1, 2, 3, 4). The nD-value regression models almost perfectly predicted the various times derived from a number of simulated survival curves exhibiting a wide variety of the operating conditions (R(2)=0.990-0.995). The nD-values were found to decrease with decreasing a(w0), and increasing T and F. The influence of a(w0) on nD-values seems to become more significant at some critical value of a(w0), below which the variation is negligible (0.93 for 1D-value, 0.90 for 2D-value, and

Ground beef, boneless skinless chicken breast meat, and boneless skinless trout fillets were inoculated with Escherichia coli O157:H7 and incubated to approximately 109 colony forming units per gram (CFU/g). Following incubation, temperature of the meat samples was equilibrated to −20, 4, and 22 °C. The meat samples at different temperatures were subjected to one-sided electron beam (e-beam) with fixed energy at 10 million electron volts (MeV) and doses at 0 (control), 0.5, 1.0, 2.0, 2.5, and 3.0 kGy. The survivors were enumerated using a standard spread-plating method. The survivor curves were plotted on logarithmic scale as a function of e-beam dose for each meat sample subjected to e-beam at different temperatures. The D-values were calculated as a negative reciprocal of the slope of the survivor curves. The D-values for E. coli ranged from 0.22 to 0.35 kGy in trout at 4 °C and chicken at −20 °C, respectively. The D-values were different between meat types. Regardless of temperature, E. coli in chicken had highest D-value followed by beef and trout. The D-values for E. coli in frozen samples were higher than D-values in samples irradiated at 4 and 22 °C regardless of species. Although there were numerical differences between D-values for samples subjected to e-beam while chilled (4 °C) or frozen (−20 °C), they were statistically insignificant. Water radiolysis is considered as an indirect mechanism for microbial inactivation. Therefore, while the physical state of water (frozen or unfrozen) in foods seems the major contributor to microbial inactivation by e-beam due to water radiolysis, product temperature most likely plays a minor role.

A detailed kinetic study on the thermal inactivation of alkaline phosphatase (ALP) added into buffer and pasteurized milk and for ALP naturally present in raw cow's milk has been performed. Kinetic parameters (rate constant, k; decimal reduction time, D; activation energy, Ea; and z value) were evaluated based on the first-order rate model at 50–80C. The temperature sensitivity of the kinetic parameters was evaluated considering the Arrhenius-type Ea model. All kinetic behaviors were well described by the first-order model (r2 > 0.91). The D values increased with increasing temperature. Higher temperatures resulted in higher rates of enzyme inactivation as indicated by lower D values and higher k values. There are significant differences (P

Prevention of browning in pineapple puree by thermal inactivation of enzyme, Polyphenoloxisase (PPO), was examined between 40 and 90 °C and in relation to exposure time. The amount of inactivation was measured as a function of time and temperature under isothermal conditions. Reaction rate constant and activation energy (Ea) as well as Decimal reduction time (D) and z-value of thermal inactivation, were determined. The rate of inactivation varied with temperatures and follows a logarithmic law. Kinetic studies showed that the thermal inactivation (40–90 °C) of the PPO followed first-order kinetics.

y combat y combat y combat rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce overheating. This technology was explored to produce shelf-stable egg products for combat ration development. overheating. This technology was explored to produce shelf-stable egg products for combat ration development. overheating. This technology was explored to produce shelf-stable egg products for combat ration development. overheating. This technology was explored to produce shelf-stable egg products for combat ration development. overheating. This technology was explored to produce shelf-stable egg products for combat ration development. Clostridium spor Clostridium spor Clostridium spor Clostridium spor Clostridium sporogenes (PA 3679) spor A 3679) spor A 3679) spor A 3679) spor A 3679) spores were used as a surr e used as a surr e used as a surr e used as a surr e used as a surrogate to v ogate to v ogate to v ogate to v ogate to validate the RF ster alidate the RF ster alidate the RF ster alidate the RF ster alidate the RF sterilization pr results of the microbial challenge study showed that microbial destruction from the RF process agreed with results of the microbial challenge study showed that microbial destruction from the RF process agreed with results of the microbial challenge study showed that microbial destruction from the RF process agreed with results of the microbial challenge study showed that microbial destruction from the RF process agreed with sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness ( ( ( ( (L*) and redness ( *) and redness ( *) and redness ( *) and redness ( *) and redness (a*). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment *). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment *). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment *). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment *). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF-treated samples. of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF-treated samples. of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF-treated samples. of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF-treated samples. of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF-treated samples. This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both military and civilian uses. military and civilian uses. military and civilian uses. military and civilian uses. military and civilian uses. K K K K Keywor eywor eywor eywor eywords: dielectr

The effects of continuous (50,000, 60,000 and 70,000 psi with holding times of 5 and 10 min) and discontinuous (oscillatory) (six cycles at 60,000 psi with a holding time of 20 s) high hydrostatic pressure (HHP) treatments on the viability of two Salmonella Enteriditis strains (FDA and PT30) inoculated onto raw almonds were evaluated at 25, 50, and 55 °C. Complete inactivation of the S. Enteriditis was achieved in 0.1% peptone water after continuous pressurization at 60,000 psi and 25 °C for 5 min. Continuous pressurization of raw almonds inoculated with S. Enteriditis at 60,000 psi and 50 °C for 5 min resulted in less than a log reduction (log 10 0.83) of vegetative cells. The decimal reduction time using the continuous pressurization parameters was determined to be 9.78 min. A discontinuous process consisting of six cycles of pressurization at 60,000 psi and 50 °C for 20 s provided greater than a one log reduction (log 10 1.27 for FDA and log 10 1.16 for PT30) of the S. Enteriditis concentration. The low water activity ( a w ) of the almonds was found to impart baroprotective attributes on the S. Enteriditis cells. When the almonds were directly suspended in water and then pressurized, a log 10 reduction of 3.37 was achieved. HHP of certain dry foods appears to be feasible if the food is directly suspended in the pressurizing medium (water).

The degradation and its corresponding color change of cyaniding-3-glucoside (Cy-3-glu) exposed to pulsed electric field (PEF) was investigated in the study. In an aqueous-methanol solution of H2O (0.5% TFA) and methanol (MeOH) (7:3, v/v), the degradation of Cy-3-glu, which was exposed to PEF at 1.2, 2.2 and 3.3 kV/cm, was increased as the electric field intensity and the treatment time increased (p

The inactivation of Salmonella Senftenberg 775W by ultrasonic waves (20 kHz, 117 μm) under pressure (175 kPa) treatments at sublethal (manosonication; MS) and lethal temperatures (manothermosonication; MTS) in media of different water activities has been investigated. Heat decimal reduction time values increased up to eighteen fold when the water activity was decreased from > 0.99 to 0.93 at 65 °C, but hardly increased the MS resistance. In reduced water activity media ( a w of 0.96 and 0.93) a synergistic lethal effect was observed between heat and ultrasound under pressure, being the inactivation rate of Salmonella Senftenberg 775W three times faster than the expected additive rate considering an effect of both bacterial lethal processes. An empirical mathematical equation enabled to predict the D MS and D MTS values obtained at different temperatures and a w in the ranges investigated of Salmonella serovars and also the microbial level of inactivation due to the synergistic lethal effect of MTS treatments in media of reduced a w . This work could be useful for improving sanitation and preservation treatments of foods, especially those in which components protect microorganisms to heat.

An effective thermophilic composting bioreactor, in which a homogenous distribution of temperature was maintained at 63-65°C by the addition of a bioavailable carbon and low mixing, was developed. The bioreactor operated on a mixture of tomato plant residues-wood shavings-municipal solid waste compost infected with tobacco mosaic virus (TMV). The initial C: N ratio and moisture content of the compost mixture were adjusted to 30:1 and 60%, respectively. The composting process was successful in destroying the tobacco mosaic virus. The results showed that the ability of the untreated virus (inoculum) to infect tobacco plants (150 LL L-1) was much higher than its ability to infect tomato plants (22 LL L-1). The TMV completely lost its ability to infect the leaves of susceptible hosts (tobacco and tomato plants) after 96 hrs of controlled thermophilic (63-65 oC) composting (or 126 h from the start of the composting process). Semilog plots of the ratio of the infection ability of the surviving virus to that of the initial inoculum (as measured by the number of local lesions) were developed. The decimal reduction time (the time necessary to reduce the infection ability of TMV by 1-log or 90%) was found to be 62.4 and 109.7 hrs for tobacco and tomato plants, respectively. The relatively short time required for complete inactivation of TMV in this study was achieved as a result of the extension of the thermophilic stage and maintaining a constant high temperature with a uniform temperature distribution by the continuous addition of the proper amount of bioavailable carbon (used cooking oil) and low mixing.

The definitive version is available at ww3.interscience.wiley.com.; International audience; Aims: In this study, the heat resistance of coliform species isolated from cooked ham and ready-made meals was determined. Methods and Results: Thirteen coliform strains belonging to 12 different species were studied using laboratory medium in order to determine δ (first decimal reduction time) and zT values temperature increase leading to a 10-fold reduction of δ) using the Weibull model. For seven strains, δ-values were determined at temperatures ranging from 55 to 60°C, with, δ values between 0-52 and 2-98 min, at 59°C. For the other six strains, lower temperature values were determined with δ-values ranging from 0-47 to 1-64 min at 54°C. zT values calculated for the 13 strains were 3-1 to 7-5°C. For eight strains, plotting of the log of survivors was not linear but rather showed shoulders or shoulders and tails. Conclusions: Coliform species were sensitive to heat treatment with a decimal reduction time under 2 min at 60°C. Significance and Impact of the Study: The better knowledge of coliform heat resistance by determining thermal resistance parameters with confidence intervals will be useful for evaluating the efficiency of industrial thermal processes.

Currently, the sterility of heat-processed food and pharmaceuticals is assessed in terms of an F0 value, based on the equivalence of the heat treatment to an isothermal process at a reference temperature. This F0 value, however, has a meaning if, and only if, the inactivation kinetics of the targeted spores (or cells) follow a first-order relationship and the temperature dependence of the D value, the reciprocal of the rate constant, is log-linear. There is growing evidence that these conditions are not satisfied by many spores, including those of Clostridium botulinum and vegetative cells. Consequently, a replacement for the F0 value is proposed in the form of a momentary equivalent time at the reference temperature based on the actual survival pattern of the spores, which need not be log-linear. This equivalent time can be calculated together with the theoretical survival ratio in real time, thus enabling an operator to monitor the lethality of ongoing industrial heat processes. The concept is demonstrated with published survival data of C. botulinum, for which the Weibullian and log-logistic models served as primary and secondary models, respectively. The safety factor according to the proposed method is in the number of added minutes of processing, beyond the theoretical time needed to reduce the survival ratio of the targeted spores or cells to a level that would produce practical (or commercial) sterility. Copyright © 2006 Society of Chemical Industry

Effects of supercritical carbon dioxide (SCCO2) on the activity of horseradish peroxidase (HRP) in pH 5.6 acetate buffer solution were investigated. SCCO2 treatment could effectively inactivate HRP. Higher pressure, higher temperature, and longer treatment time caused more inactivation. The maximum reduction of HRP activity reached nearly 90% at 30 MPa and 55 °C for 60 min. Analysis of first-order reaction kinetic data (characterized by a rate constant k and by a decimal reduction time D) showed that D value was closely related to the pressure and temperature of SCCO2 treatment. Higher pressures or higher temperatures resulted in lower D values (higher k), the D value of HRP was minimized to 64.52 min treated by the combination of 30 MPa and 55 °C. The Zp, representing the range of applied pressure between which the D values change by a factor of 10, was 114.81 MPa. The activity of HRP treated by SCCO2 was reactivated significantly after initial 7-day storage at 4 °C apart from the samples at 30 MPa for 60 min, indicating the HRP inactivation may be reversible and the reactivation of HRP is dependent on the pressure level and treatment time.

A Clostridium sp. RKD isolated from the intestine of decaying fish, showing 99% sequence identity with Clostridium tetani at a 16S rRNA level, produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E). It also showed an amplification of near-expected size when polymerase chain reaction (PCR) was performed using group- and type-specific primers for botulinum neurotoxin type B. The isolate exhibited differences with both C. tetani and Clostridium botulinum with respect to phenotypic characteristics and chemotaxo-nomic markers. Spore production was optimized with respect to media composition and stage of growth. Time-dependant examination of sporulation revealed 2.6% to 49.0% spores in the late stationary phase culture when grown in different broth media. A simpler method for spore production and isolation from culture grown in tryptose sulfite cycloserine (TSC)/anaerobic agar sandwich resulted in >95% sporulation, which could be purified to near homogeneity by a simple 2-step procedure. Thermal resistance of spores revealed a biphasic inactivation at lower temperatures with D values for linear inactivation varying from 26.6, 8.0, and 4.3 min at 70 °C, 80 °C, and 90 °C, respectively. The z values of 7.86 °C and 10.47 °C were obtained in the linear and tail regions, respectively. The Weibull parameter b values at 70 °C, 80 °C, and 90 °C were 27.38, 3.55, and 0.99, respectively, with a z’ value of 13.869 °C. The shape parameter n at 70 °C, 80 °C, and 90 °C were 0.63, 0.55, 0.45, respectively. Spores produced on 2 different media (cooked meat medium [CMM] and trypticase peptone yeast-extract glucose [TPYG] agar) exhibited differences in heat resistance. The addition of lysozyme (50 jj.g/mL) before heat treatment resulted in increased thermal resistance of spores.

Fresh, different meat types and offal were examined for the occurrence of Aeromonas species by the direct-plating and enrichment methods. The enrichment method (coefficient of variation = 15.1%) enhanced the recovery of Aeromonas species. The major Aeromonas species identified were A. sobria (67.3%) and A. hydrophila (21.2%). Other species occurred in minor proportions and were A. caviae, A. proteolytica and A. salmonicida. Out of the 52 isolates, 50 were motile species except two which were not motile and identified as the species A. proteolytica. Sixteen motile species occurred in cow, 18 in goat and 16 in lamb. The motile species and the two nonmotile species were hemolytic. They were all sensitive to chloramphenicol (30 mg) and resistant to ampicillin (10 mg). The nonmotile A. proteolytica were all resistant to tetracycline. Aeromonas caviae, A. salmonicida, A. hydrophila and A. sobria were killed after exposure to 50C (decimal reduction time, D 10 = 30 s). Aeromonads are unlikely to pose a public health problem in Nigeria where meat undergoes prolonged cooking. Meat is a possible factor in the epidemiology of Aeromonas-associated gastroenteritis in man.

The suitability of shell sand as a P sorbent has been tested both with laboratory batch experiments as well as in a sub-surface flow (SSF) meso-scale constructed sand filter treating municipal wastewater from a single household. The batch experiments suggest that retention of P in shell sand occurs both as sorption and precipitation. The soil–water ratio was found to be a crucial parameter when performing laboratory batch experiments. The maximum retention capacity was about 8000 and 800 mg P kg −1 sand, and the K d was 33.7 and 82.9 L kg −1 for soil–water ratios of 5 g–75 mL and 50 g–50 mL, respectively. The average total accumulated P concentration in samples from the SSF sand filter was 335 mg P kg −1 . The K d value based on [PO 4 3− ] and accumulated concentration of inorganic P in the SSF filter was 89.8 L kg −1 . Thus the batch experiments overestimated the retention capacity of shell sand in real sand filter systems, however, a ratio of 50–50 gave a more reasonable estimate than a ratio of 5–75. The K d value from batch samples with a ratio of 50–50 also gave a good estimate of the K d value in the constructed sand filter. Ca–P was found to be the predominant form of P mineral in samples collected from the SSF sand filter. Some Al–P, loosely bounded P, and occluded P were also present in the sand.

Several factorial models extending the famous Bigelow model to describe the influence of the heating and recovery pH and aw conditions on bacterial heat resistance have been developed. These models can be associated in an overall multifactorial model describing the influences of heating and recovery conditions on D values. For Bacillus cereus strain ADQP 407 the model parameters characterising the environmental factor influences (pH, Temperature, aw) were evaluated. Determination of bacterial heat resistance in cream chocolate have been realised to validate these parameter values and to evaluate the level of the influence of food texture or different compounds not taken account of in the model.