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Cloudy apple juice has been treated by high pressure carbon dioxide (HPCD) as non-thermal technology to inactive polyphenoloxidase and pectinmethylesterase in batch mode. Stirring speed (from 200 to 600 rpm) induced an increase in the enzyme inactivation rate while a triple cycle of pressurization/depressurization led to the same enzyme inactivation efficiency. Enzyme inactivation kinetics were determined at different temperatures (from 35 to 45 °C) and pressures (from 10 to 20 MPa). Data were described by the first order kinetic model and the Weibull model. For the first order kinetic model, decimal reduction time for HPCD treatment was found to be smaller than for mild heating, in the same temperature range. The same tendency was observed for the first decimal reduction time in the Weibull model. HPCD treatment resulted in a homogenization effect reflected in the shifting of the particle size distribution towards smaller diameters after treatment. HPCD treatment did not result in a change of water and oxalate soluble pectin content, total phenolic compounds and hidroxymethylfurfural content., Spanish Government (MINECO) and the European Regional Development Fund for financial support of project CTQ2015-64396-R and AEI’s contract.

We report the development of hydrodynamic cavitation coupled with thermal treatment for reducing counts of B. coagulans (ATCC 12245) in skim milk concentrate (SMC, 35 ± 1% total solids). The process was evaluated in terms of analysis of cavitation parameters, characterization of the increase in the fluid temperature, and microbial inactivation. Inoculated SMC (4.67 ± 0.18 log) was treated by cavitation (rotor speed of 3600 RPM and fluid flow rate of 100 L h−1), thermal treatment (75–85 °C for 14–106 s), or a combined cavitation-thermal treatment, using the aforementioned conditions. A 3.5 log CFU mL−1 reduction was obtained by the combined cavitation-thermal treatment, while thermal treatment alone yielded a 2.77 log CFU mL−1 reduction. Contrary, individual cavitation did not produce a significant reduction. The values of decimal reduction time at 75 °C (D75) were lower when cavitation was followed by thermal treatment (375 ± 62 s) than the values obtained for thermal treatment (470 ± 66 s). The outcomes of this study present opportunities for reducing the counts of B. coagulans in skim milk concentrate by the combined effect of hydrodynamic cavitation and thermal treatment.

Inactivation kinetics of polyphenol oxidase (PPO) by a two-stage method which was additionally pressurized at ambient temperature after carbon dioxide microbubbles (MB-CO 2 ) was mixed with a solution at low temperature and pressure (two-stage MB-CO 2 ) was analyzed. The PPO inactivation efficiency of the two-stage MB-CO 2 treatment was higher than that of heat treatment. A decrease in the decimal reduction time ( D value) and activation energy during PPO inactivation using the two-stage MB-CO 2 treatment was observed as the temperature of the heating coil and the pressure in the mixing vessel increased. The temperature rise required for a 90% reduction in the D value was increased. Furthermore, the pressure rise required for a 90% reduction in the D value and activation volume increased with the temperature of the heating coil. These results showed that PPO inactivation using the two-stage MB-CO 2 treatment could be achieved with less energy than heat treatment.

The inactivation of polyphenoloxidase (PPO) and peroxidase (POX) in red beet by traditional and microwave (MW) blanching was studied. Microwave heating effects on color and texture were also studied. Red beet subjected to MW blanching for 5 min at 100–200 W resulted in large weight losses accompanied by a high degree of shrinking. POX was the more heat resistant enzyme. The 90% destruction (D value) of the activity of both enzymes could be achieved only at 200 W within the 5 min frame employed for the tests. When the samples were immersed in water and both the food sample and the water were submitted to MW exposure at 250–450 W or variable power with a maximum at 935 W, shrinking was avoided. The D value at 90 °C (reference; ) and z could be determined after time–temperature corrections, and it was observed that, in general, values for POX were smaller than for PPO. The microwave treatment (maximum power: 935 W) designed to provide a similar temperature profile to the one observed for traditional blanching (immersion in water at 90 °C), showed the smallest value for POX inactivation. All treatments reduced elastic characteristics and changed the color of the tissues showing a shift to blue mainly in the case of microwave processes., The authors acknowledge the financial support from University of Buenos Aires (EX-089), National Agency of Scientific and Technological Promotion of Argentina (ANPCyT-PICT 38239) and National Scientific and Technical Research Council of Argentina (CONICET-PIP 11220090100531).

The efficacy of a scale-up of a moderately high pressure unit built in this work was investigated with regards to inactivation of Geobacillus stearothermophilus spores suspended in pumpkin soup, and effect of the process on l -ascorbic acid. In this design saturated steam was used as a heating medium. The treatment unit is a double pipe heat exchanger in which the food is pumped in its inner tube, while steam is passed in the annular region to heat the sample. This technology comprises a unique approach of generating a mild pressure (80–100 MPa) utilizing thermal expansion of the liquid being treated. The results show that this unique application decreased the D-values of Geobacillus stearothermophilus ATCC 7953 spores suspended in soup samples in comparison to thermal treatment alone. The improvement was more significant at lower treatment temperatures. The D-values obtained were in a good agreement with that of the small unit built earlier in which oil was used as a heating medium. The effect of treatment on l -ascorbic acid was similar to that of thermal treatment. The treated samples were subjected to shelf life study by storing them at two different temperatures. No evidence of spore recovery was noted during the post-treatment storage period.

Monte Carlo procedures can be used to evaluate the uncertainty of food safety and quality estimations associated with the variability in the parameters for the calculation model used. Procedures for possible inclusion in an undergraduate process engineering course covering the assessment of uncertainty in thermal processing decisions were developed using spreadsheets and operations found in the Excel™ Analysis ToolPack. Published thermal decimal reduction time (DT, T = 110 °C) and initial spore load (No, spores/container) level for Clostridium botulinum Type B in mushroom were used to estimate a thermal processing time (FT). For a survival probability (N) of 1 spore in 109 containers and using mean values for the parameters DT and log No yielded F110°C = 5.96 min. Unique combinations of D T ∗ and N o ∗ datasets generated assuming normal and lognormal distributions, respectively, were used to obtain the distribution for the spore survival probability and the associated percentage of under processing. Next, the coefficient of variation (CV) for the percentage of under processing based on 2–500 generated datasets was calculated and used as a criterion to determine that 100 was an acceptable minimum number of datasets to estimate a recommended thermal process (F110°C = 9.6 min) considering the reported variability of the parameters DT and No. This thermal process would yield a 10−9 failure rate with a 95% confidence based on the frequency distribution for spore survival probability. The same procedures were used to assess the impact of lowering the standard deviation of both No and D110°C by 10%, 50%, and 90% yielding 8.6, 7.8, and 6.4 min, respectively, as a recommended thermal process at 110 °C with 95% confidence.

The use of infrared (IR) heating for improving the microbial safety and processing efficiency of dry-roasted almonds was investigated. Almonds were roasted at 130, 140 and 150 °C with three different methods: IR roasting, sequential infrared and hot air (SIRHA) roasting, and traditional hot air (HA) roasting. The heating rate and pasteurization efficacy of almonds under different roasting methods and temperatures were evaluated. Pediococcus sp. NRRL B-2354 was used as a surrogate for Salmonella enterica Enteriditis PT 30 for evaluating the pasteurization efficacy of different processing methods and conditions. When SIRHA roasting at 130, 140 and 150 °C roasting temperatures was used to produce medium roasted almonds, 4.10-, 5.82- and 6.96-log, bacterial reductions were achieved with 38%, 39% and 62% time saving compared to HA roasting at each temperatures, respectively. The decimal reduction time of the bacteria at all roasting temperatures were calculated for SIRHA roasting as 8.68, 3.72 and 1.42 min, respectively, with a correlation coefficient greater than 0.92 and the thermal resistance constant was found as 25.4 °C. The total color change followed zero-order reaction kinetics and the activation energies were 73.58, 52.15 and 67.60 kJ/mol for HA, IR and SIRHA roasting, respectively. No significant difference (p > 0.05) was observed in sensory quality of medium roasted almonds processed with different roasting methods. We conclude that the SIRHA roasting is a promising new method for the production of dry-roasted pasteurized almonds.

The inactivation kinetics of enzymes polyphenol oxidase (PPO) and peroxidase (POD) was studied for the batch (discontinuous) microwave treatment of green coconut water. Inactivation of commercial PPO and POD added to sterile coconut water was also investigated. The complete time–temperature profiles of the experimental runs were used for determination of the kinetic parameters D-value and z-value: PPO ( D 92.20 °C = 52 s and z = 17.6 °C); POD ( D 92.92 °C = 16 s and z = 11.5 °C); PPO/sterile coconut water: ( D 84.45 °C = 43 s and z = 39.5 °C) and POD/sterile coconut water: ( D 86.54 °C = 20 s and z = 19.3 °C). All data were well fitted by a first order kinetic model. The enzymes naturally present in coconut water showed a higher resistance when compared to those added to the sterilized medium or other simulated solutions reported in the literature. The thermal inactivation of PPO and POD during microwave processing of green coconut water was significantly faster in comparison with conventional processes reported in the literature.

The effect of organic acid (either citric or acetic) on thermal inactivation of Geobacillus stearothermophilus (former Bacillus stearothermophilus) spores was analysed focusing on individuals of population with different thermal sensitivity. The survival of spores was investigated in media (tryptone solution, red beet juice) of natural pH or acidified with organic acid at pH ranging from 6.0 to 4.0. Thermal sterilisation was carried out in the temperature range from 115 °C to 125 °C. It was confirmed that survival curves of G. stearothermophilus spores could have three stages, which caused that the decimal reduction time was not always a proper parameter to set the conditions required for the media sterilisation. Based on performed experiments it was found out that spore inactivation in acidified red beet juice medium was faster than in acidified tryptone solution. It was shown that the presence of both acetic and citric acids in tryptone solution had a similar influence on the rate of spore inactivation. However, in the case of red beet juice, the acetic acid had a stronger effect on spore destruction than the citric acid only at pH 4.0. It was proved that medium composition could accelerate the activation of dormant spores, what resulted in elimination of “tailing” on the spore survival curve and in shorter time necessary for inactivation of particular spore population.

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.

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.

The kinetic parameters of models that describe the joint influence of water content and temperature on the thermal degradation of ascorbic acid were estimated from drying experiments using maltodextrin DE 12 as a base material. Two models were used: a first-order decay model with (1) a TDT temperature dependency and a polynomial dependency of the Dr and z values with water content, and (2) a WLF dependency of the D value on glass transition temperature, with the Gordon–Taylor equation describing the influence of water content on Tg. Experiments were performed in a drying oven with dry bulb temperatures between 100°C and 160°C, with most of the drying occurring with the sample temperature below the oven temperature. Both models provided good fits of the experimental data. Other data from literature for a very different temperature range (4°C–68°C) and for maltodextrin DE 25 were handled in the same way and while the polynomial/TDT model yielded a different moisture dependence structure, the WLF/Gordon–Taylor model yielded similar parameters, thus showing a better predictive power.

This study was carried out to evaluate inactivation kinetic parameters (rate constant, k, and decimal reduction time, D) of Listeria monocytogenes based on the first-order rate model in Turkish Feta cheese. All kinetic behaviour studies were well described by the first-order model (R2>0.91). The rate of microbial reduction was higher in cheese made with starter than the cheese made without starter as indicated by the associated lower D values. There were significant differences (P

The aim of the research work was to develop an experimental method to obtain kinetic data for the thermal inactivation of micro-organisms, with regard to active survivors in the food itself. The method is based on the principle that the number and concentration of surviving active microbes can be assessed from the number of spoiled heat treated units (m) out of a sample containing M units (1⩽m⩽M−1). Clostridium sporogenes spores have been inactivated in pea puree at 115°C and 121°C. The concentration of active surviving spores has been determined from the number of spoiled vials (units) out of samples of 50–50 vials at four-time periods. A very small heat resistant fraction has been detected with DT=6.32 min decimal reduction time at T=121°C, z=10.41°C temperature coefficient, N i ∗ =0.36 and 2.2 cm−3 initial concentration of spores. Active survivors are understood as those able to multiply in the specified food after heat treatment, inactive ones do not multiply in the food, but in a suitable culture medium. Total initial concentration (potentially active and inactive survivors) was 1.2×105 spores per cm3. The experimental method is applicable for low survivor concentrations and useful for industrial application, as active survivors are detected in the food itself. Inactive survivors were also found in unspoiled vials.

Aerated biological reactors at a laboratory scale, fed continuously with a model wastewater system, were used to obtain design parameters of an activated sludge process for the wastewater treatment of a potato processing plant. Experiments were performed using different dilution rates ( D ) ranging between 0.01 and 0.13 h −1 to determine parameters such as: maximum specific microbial growth rate ( μ max ), saturation constant ( K s ), coefficient of microbial decay ( k d ) and true biomass yield ( Y X/S ). Design parameters were calculated from the mass balances of substrate consumption and biomass production under steady state, considering a Monod-type equation to represent the effect of substrate concentration on biomass production rate. The values of Y X/S and k d were obtained from the linear plot of q S (specific rate of substrate consumption) vs. D . Experimental data regression led to Y X/S =0.45 gVSS/g COD and k d =0.024 h −1 . By non-linear regression of q S vs. substrate concentration ( S S ) data the following values were obtained μ max =0.09 h −1 and K s =0.006 g/l. Critical dilution rate was also calculated; it corresponds to the D value for which the cells of a reactor operating under such conditions are destroyed or are eliminated from the system at the same rate than they are produced.