Rate Of Microbial Inactivation Research Articles

SODIS with hydrogen peroxide: an effective household water treatment option under sub-tropical climatic conditions of bangladesh.

Solar disinfection (SODIS) is an affordable and sustainable Household Water Treatment (HWT) method endorsed by WHO. However, its limitations include longer sunlight exposure requirements, incomplete microbial inactivation, and post-SODIS microbial regrowth during monsoon and winter seasons in subtropical climates. To address these limitations, the performance of SODIS with H2O2 for microbial inactivation during the monsoon and winter seasons in Bangladesh was evaluated following the WHO HWT protocols. Moreover, the process was verified using drinking water samples collected from restaurants, households, and slums. All SODIS experiments were conducted using reflective reactors with PET bottles and plastic bags, adding 10 mg/L of H2O2, and exposing them to sunlight for 6 h. The results showed that E. coli was completely inactivated within 2 h in plastic bags and within 3 h in PET bottles during the monsoon season, achieving an LRV of > 5. In winter, both achieved an LRV > 5 within 3 h and plastic bags showed more efficient in microbial inactivation than PET bottles. The microbial inactivation rates were 5 times higher than those of conventional SODIS. No regrowth of microorganisms was observed during the subsequent post-SODIS period of 12 h and 24 h at room temperature. The study findings suggest that SODIS with H2O2 has the potential for complete microorganism inactivation with shorter sunlight exposure in subtropical climates with moderate to low solar irradiation and can be adopted as a reliable disinfection option for rural and urban communities with unsafe drinking water supply.

Potassium ferrate's disinfecting ability: a study on human adenovirus, Giardia duodenalis, and microbial indicators under varying pH and water temperature conditions

ABSTRACT Ferrate (Fe(VI): HFeO4− /FeO42−), a potent oxidant, has been investigated as an alternative chemical disinfectant in water treatment due to its reduced production of disinfection by-products. In this study, we assessed the disinfecting ability of potassium ferrate against a variety of microorganisms, including waterborne pathogens, under varying pH and water temperature conditions. We presented CT values, a metric of ferrate concentrations (C) and contact time (T), to quantify microbial inactivation rates. Among the tested microorganisms, human adenovirus was the least resistant to ferrate, followed by waterborne bacteria such as Escherichia coli and Vibrio cholerae, and finally, the protozoan parasite Giardia duodenalis. We further investigated the impact of two pH values (7 and 8) and two temperatures (5 and 25 °C) on microbial inactivation rates, observing that inactivation rates increased with lower pH and higher temperature. In addition to showcasing ferrate's capacity to effectively inactivate a range of the tested microorganisms, we offer a ferrate CT table to facilitate the comparison of the effectiveness of various disinfection methods.

Pilot-scale plasma activated water treatment for decontaminating romaine lettuce and steamed rice cakes

The study investigated the effects of pilot-scale plasma activated water (PAW) on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and indigenous mesophilic aerobic bacteria on romaine lettuce and steamed rice cake (SRC). PAW treatment was conducted by stirring 25 g of romaine lettuce and 80 g of SRC for 20–40 min at 195 rpm in 1 L of PAW, prepared by treating sterile distilled water with surface dielectric barrier discharge for 40 or 60 min. The microbial inactivation rates of foodborne pathogens and indigenous mesophilic aerobic bacteria ranged from 1.3 to 2.5 log on romaine lettuce and SRC, along with PAW generation time (P < 0.05). Inactivation rates of PAW generation time or treatment time against romaine lettuce and SRC were significantly different to the inactivation of distilled water treatments, respectively (P < 0.05). The pH, electrical conductivity, and hydrogen ion concentration correlated with nitrite and nitrate concentrations of PAW prepared at various PAW generation time. In situ pilot-scale PAW treatment also extended the shelf life of the romaine lettuce. The study demonstrates the feasibility of the pilot-scale PAW treatment to improve microbiological safety and its suitability of applying PAW to manufacture romaine lettuce and SRC products.

Cold atmospheric pressure air plasma jet disinfection of table eggs: Inactivation of Salmonella enterica, cuticle integrity and egg quality

Eggshell cuticles are first lines of defense against egg-associated pathogens, such as Salmonella enterica serovar Enteritidis (SE). Infections from eggs contaminated with this strain remain a significant risk. In addition, changes in the cuticle are closely related to changes in egg safety. The emerging non-thermal atmospheric pressure plasma technology enables a high rate of microbial inactivation at near-ambient temperatures, making it ideal for food safety applications. This study examines the effects of a cold atmospheric pressure air plasma jet (CAAP-J) on eggshell cuticle and egg quality whilst inactivating SE. Shell eggs inoculated with SE (7 log10 cfu/egg) were used as the samples to test the decontamination performance of the device. The tests were conducted using an industrial CAAP-J with different power levels (600–800 W), exposure times (60–120 s), at a fixeddistance of 20 mm from the plasma jet and an air flow rate of 3600 L/h. It was found that the best results were obtained after 120 s at maximum plasma power (800 W). Subsequent to the implementation of this plasma procedure, it was determined that no viable cells could be detected. After CAAP-J treatment, the temperature remains below 50.5 °C, thereby minimizing the risk of altering egg quality. All specific measurements (egg white pH, yolk pH, yolk color, HU, and eggshell breaking strength) have shown that CAAP-J treatment has no negative effect on egg quality. No changes in eggshell cuticle quality after CAAP-J treatment was confirmed through scanning electron microscope (SEM).

Modeling and optimization of synergistic ozone-ultraviolet-chlorine process for reclaimed water disinfection: From laboratory tests to software simulation.

The ozone-ultraviolet (UV)-chlorine process is a highly effective method of disinfection in water reuse system, but currently still lacks precise quantification and accurate control. It is difficult to determine the dosage of each disinfectant because of the complex interactions that occur between disinfection units and the complicated mathematical calculation required. In this study, we proposed a dosage optimization model for ozone-UV-chlorine synergistic disinfection process. The model was able to identify the cost-effective doses of the disinfectants under the constraints of microbial inactivation, decolorization, and residual chlorine retention requirements. Specifically, the simulation of microbial inactivation rates during synergistic disinfection process was accomplished through quantification of the synergistic effects between disinfection units and the introduction of enhancement coefficients. In order to solve this optimization model rapidly and automatically, a MATLAB-based software program with graphical user interface was developed. This software consisted of calibration unit, prediction unit, assessment unit, and optimization unit, and was able to simulate synergistic ozone-UV-chlorine process and identify the optimal dose of ozone, UV, and chlorine. Validation experiments revealed good agreements between the experimental data and the results calculated by the developed software. The developed software is believed to help the water reclamation plants improve disinfection efficiency and reduce the operational costs of synergistic disinfection processes.

Predictive models in the ultrasonic disinfection of hospital-effluents: a review and suggestion for future research

At the end of this review on applications of ultrasonic waves in the inactivation of microorganisms in hospital laundry effluents, the fourth type of predictive model is proposed, based on the application characteristics of the experimental plans. The number of works for the disinfection of wastewater by ultrasound waves (US) associated with other techniques or individuals has been increasing. The use of ultrasound to produce lethal effects on microorganisms is attractive because it is considered a "green" technology in that it involves sound energy and does not require additional chemicals, or a very small amount. Also, the US as a tool for water reuse processes - operates at low pressure and temperature and does not produce toxic or greenhouse gases. Hospital laundry effluents are characterized by different microorganisms, a fact that can hinder the application of conventional physical-chemical technologies. To contribute to future developments in the application of ultrasound (US), this work uses some typical US applications in the disinfection of aqueous effluents. To propose strategies for carrying out new works, comments are made regarding an approach oriented towards new advances based on the need to interrelate the variables involved in the studies, at the same time that these variables are correlated with the rate of inactivation. For this, it is discussed the predictive models and their contributions, according to the number of factors that should be involved for a better understanding of the rate of microbial inactivation.

Bayesian global regression model relating product characteristics of intermediate moisture food products to heat inactivation parameters for Salmonella Napoli and Eurotium herbariorum mould spores

Thermal inactivation of pathogenic and spoilage organisms in low and intermediate moisture foods is of critical importance for guaranteeing microbiological safety and stability of these products. Producers tendentially reduce salt in low and intermediate moisture foods because of nutritional health considerations, but it is unclear how this affects microbial inactivation rates during pasteurization. In this study we predict the time to achieve a pre-defined 6-log reduction for Salmonella enterica subsp. enterica serovar Napoli (hereafter: S. Napoli) and Eurotium herbariorum mould spores (hereafter: E. herbariorum spores) and the relationship with product characteristics. We tested 31 design products for heat inactivation of S. Napoli and 29 design products for heat inactivation of E. herbariorum spores. We used a global Bayesian regression combining primary Weibull models with a secondary regression model to relate pasteurization temperature and product characteristics (water activity (aw), pH, and fractions of sodium chloride, sucrose and oil on product) to microbial counts. With this model, we predict the time to 6-log reduction. Thermal inactivation rates were much higher for vegetative S. Napoli than for E. herbariorum spores. Also, inactivation curves were non-linear for many experiments. There were significant associations between the Weibull model parameters and temperature, and pH and aw for S. Napoli and E. herbariorum spores, respectively. We parameterized an inactivation model for S. Napoli and E. herbariorum spores using design products with a broad range of characteristics and showed how the simplified approach of using D-values does not accurately describe the non-linearity of thermal inactivation for both types of organism. Results of our model can be used to produce accurate heat inactivation predictions as input for the pasteurization process in factories where intermediate moisture foods are manufactured.

Natural inactivation of MS2, poliovirus type 1 and Cryptosporidium parvum in an anaerobic and reduced aquifer

The study of microbial inactivation rates in aquifer systems has most often been determined in aerobic and oxidized systems. This study examined the inactivation (i.e. loss of infectivity) of MS2, poliovirus type 1 (PV1) and Cryptosporidium parvum in an anaerobic and reduced groundwater system that has been identified as storage zones for aquifer storage and recovery (ASR) facilities. Anaerobic and reduced (ORP<- 250mV) groundwater from an artesian well was diverted to an above-ground, flow-through mesocosm that contained diffusion chambers filled with MS2, PV1 or Cryptosporidium parvum. The respective infectivity assays were performed on microorganisms recovered from the diffusion chambers during 30- to 58-day experiments. The net reduction in infectivity was 5.73log10 over 30days for MS2, 5.00log10 over 58days for PV1 and 4.07log10 over 37days for C. parvum. The best fit inactivation model for PV1 was the log-linear model and the Weibull model for MS2 and C. parvum, with respective inactivation rates (95% confidence interval) of 0.19 (0.17-0.21) log10 day-1 , 0.31 (0.19-0.89) log10 day-1 and 0.20 (0.14-0.37) log10 day-1 . The groundwater geochemical conditions in this aquifer enhanced the inactivation ofMS2, PV1, and C. parvum at rates approximately 2.0-5.3-fold, 1.2-17.0-fold, and 4.5-5.6-fold greater, respectively, than those from published studies that used diffusion chambers in aerobic-to-anoxic groundwater systems, with positive redox potentials. Geochemical conditions like those in the aquifer zone in this study can naturally and significantly reduce concentrations of microbial indicators and pathogens of human health concern in injected surface water. Appropriate storage times for injected surface water could complement above-ground engineered processes for microorganism removal and inactivation (e.g. filtration, disinfection) by naturally increasing overall microorganism log-inactivation rates of ASR facilities.

Processing sheep milk by cold plasma technology: Impacts on the microbial inactivation, physicochemical characteristics, and protein structure

This study aimed to evaluate the impacts of cold plasma processing time of 30 s, 180 s, and 300 s (CSM30, CSM180, and CSM300) on the microbial inactivation, physicochemical characteristics, and protein structure of raw sheep milk. Pasteurized sheep milk was used as the positive control. The microbial inactivation rate of CSM300 sample was similar to the pasteurized sample, and the former had a significantly smaller casein micelle size and polydispersity index (P < 0.05). The pH, and a* value decreased from 6.79 to 6.65, and −1.74 to −1.98, respectively (P < 0.05) with increasing processing time. Also, the moisture content of the freeze-dried milk decreased from 43.4 g/kg to 28.9 g/kg. The Fourier-transform infrared spectra indicated that the CSM180 and CSM300 samples had higher proportions of β-turn structures and a diminished-random coil conformation, the latter could induce an appropriate conformational transformation from α-helix to β-sheet. Scanning electron microscopy images confirmed that the CSM300 sample promoted a more uniform microstructure and a better dispersion state of proteins. These results might provide practical information regarding cold plasma–treated sheep milk, which can be considered as a potential alternative to conventional pasteurization.

A modified Weibull model for design of oscillated high hydrostatic pressure processes

During high hydrostatic pressure (HHP) processing, pressure can be applied in a single cycle of pressurization, pressure holding, and depressurization or multiple cycles. The latter is called oscillated HHP (OHHP) processing. In this study, it was hypothesized that the pressure gradient during HHP processing is positively related to the lethal rate, based on which a modified Weibull model was developed to describe the microbial inactivation rate as a function of pressure and pressure gradient. The model provided good fits to published survival data of Salmonella Enteritidis, Escherichia coli, and Listeria innocua, as indicated by small RMSE values being less than 0.33 log. Using the obtained parameters, the model showed good performance in predicting microbial survival ratios in independent tests, the absolute errors being less than 0.27 log, and both accuracy and bias factors being fairly close to 1. Based on the developed model, the pressurization rate must be higher than a critical value to make an OHHP process more efficient than a single-cycled one, and an optimal OHHP process should involve the highest pressurization and depressurization rates and no pressure holding time. Finally, a web-based software tool was developed to implement the modified Weibull model for design of OHHP processes.

Microbial Inactivation by Non-equilibrium Short-Pulsed Atmospheric Pressure Dielectric Barrier Discharge (Cold Plasma): Numerical and Experimental Studies

Microbial inactivation efficacy of plasma generated by a custom-made floating electrode dielectric barrier discharge (FE-DBD) or cold plasma at three different frequencies (1 kHz, 2 kHz, and 3.5 kHz) was experimentally evaluated for its inactivation of the pathogen surrogate Enterobacter aerogenes on a glass surface to obtain inactivation kinetics. COMSOL Multiphysics® was used to numerically simulate the amount and the distribution of reactive species within an FE-DBD system. Microbial inactivation kinetics was predicted using species concentrations and microbial inactivation rates from the literature and compared with experimental data. The results showed that the FE-DBD plasma treatment achieved a microbial reduction of 4.3 ± 0.5 log CFU/surface at 3.5 kHz, 5.1 ± 0.09 log CFU/surface at 2 kHz, and 5.1 ± 0.05 log CFU/surface at 1 kHz in 2 min, 3 min, and 6 min, respectively. The predicted values were 4.02 log CFU/surface, 4.10 log CFU/surface, and 4.56 log CFU/surface at 1 kHz, 2 kHz, and 3.5 kHz, respectively. A maximum 1 log difference was observed between numerical predictions and the experimental results. The difference might be due to synergistic interactions between plasma species, UV component of FE-DBD plasma, and/or the electrical field effects, which could not be included in the numerical simulation.

Cupric ion in combination with hydrogen peroxide and hydroxylamine applied to inactivation of different microorganisms

The microbial inactivation by cupric ion (Cu(II)) in combination with hydrogen peroxide (H2O2) and hydroxylamine (HA) was investigated for twelve different microorganisms (five Gram-negative bacteria, three Gram-positive bacteria, and four bacteriophages). The inactivation efficacy, protein oxidation, and RNA (or DNA) damage were monitored during and after treatment by Cu(II), Cu(II)/HA, Cu(II)/H2O2 and Cu(II)/HA/H2O2. The rate of microbial inactivation by the (combined) microbicides generally increased in the order of Cu(II) < Cu(II)/H2O2 < Cu(II)/HA < Cu(II)/HA/H2O2; Cu(II)/HA/H2O2 resulted in 0.18–0.31, 0.10–0.18, and 0.55–3.83 log inactivation/min for Gram-negative bacteria, Gram-positive bacteria, and bacteriophages, respectively. The degrees of protein oxidation and RNA (or DNA) damage increased in the order of Cu(II) < Cu(II)/HA < Cu(II)/H2O2 < Cu(II)/HA/H2O2. In particular, Cu(II)/HA/H2O2 led to exceptionally fast inactivation of the viruses. Gram-positive bacteria tended to show higher resistance to microbicides than other microbial species. The microbicidal effects of the combined microbicides on the target microorganisms were explained by the roles of Cu(I) and Cu(III) generated by the redox reactions of Cu(II) with H2O2, HA, and oxygen. Major findings of this study indicate that Cu(II)-based combined microbicides are promising disinfectants for different waters contaminated by pathogenic microorganisms.

Assessing the Impact of Cyanuric Acid on Bather’s Risk of Gastrointestinal Illness at Swimming Pools

Current regulatory codes for swimming pool disinfection separately regulate free chlorine (FC) and cyanuric acid (CYA). It is well-known that CYA affects disinfection rates by reversibly binding to FC in aqueous solutions. However, limits for these regulated parameters have neither systematically accounted for this chemistry nor been based on the risk of gastrointestinal illness. This study was intended to determine the minimum concentration of FC relative to CYA based on the risk of gastrointestinal illness from normal fecal sloughing of selected pathogens and to find a simple regulatory rule for jointly managing FC and CYA for consistent disinfection. Literature data on CYA’s effect on microbial inactivation rates were reanalyzed based on the equilibria governing hypochlorous acid (HOCl) concentration. A model was developed that considers the rates of pathogen introduction into pool water, disinfection, turbulent diffusive transport, and pathogen uptake by swimmers to calculate the associated risk of illness. Model results were compared to U.S. Environmental Protection Agency (EPA) untreated recreational water acceptable gastrointestinal illness risk. For Cryptosporidium, correlation between log inactivation and Chick–Watson Ct was far better when C refers to HOCl concentration than to FC (r = −0.96 vs. −0.06). The HOCl concentration had a small variation (± 1.8%) at a constant CYA/FC ratio for typical FC and CYA ranges in swimming pools. In 27 U.S. states, the allowed FC and CYA results in HOCl concentrations spanning more than a factor of 500. Using conservative values for a high bather load pool with 2 mg/L FC and 90 mg/L CYA, the model predicted a 0.071 annual probability of infection for Giardia, exceeding the EPA regulatory 0.036 limit for untreated recreational waters. FC and CYA concentrations in swimming pools should be jointly regulated as a ratio. We recommend a maximum CYA/FC ratio of 20.

Inactivation of pathogenic microorganisms in freshwater using HSO5−/UV-A LED and HSO5−/Mn+/UV-A LED oxidation processes

Freshwater disinfection using photolytic and catalytic activation of peroxymonosulphate (PMS) through PMS/UV-A LED and PMS/Mn+/UV-A LED [Mn+ = Fe2+ or Co2+] processes was evaluated through the inactivation of three different bacteria: Escherichia coli (Gram-negative), Bacillus mycoides (sporulated Gram-positive), Staphylococcus aureus (non-sporulated Gram-positive), and the fungus Candida albicans. Photolytic and catalytic activation of PMS were effective in the total inactivation of the bacteria using 0.1 mM of PMS and Mn+ at neutral pH (6.5), with E. coli reaching the highest and the fastest inactivation yield, followed by S. aureus and B. mycoides. With B. mycoides, the oxidative stress generated through the complexity of PMS/Mn+/UV-A LED combined treatments triggered the formation of endospores. The treatment processes were also effective in the total inactivation of C. albicans, although, due to the ultrastructure, biochemistry and physiology of this yeast, higher dosages of reagents (5 mM of PMS and 2.5 mM of Mn+) were required.The rate of microbial inactivation markedly increased through catalytic activation of PMS particularly during the first 60 s of treatment. Co2+ was more effective than Fe2+ to catalyse PMS decomposition to sulphate radicals for the inactivation of S. aureus and C. albicans.The inactivation of the four microorganisms was well represented by the Hom model. The Biphasic and the Double Weibull models, which are based on the existence of two microbial sub-populations exhibiting different resistance to the treatments, also fitted the experimental results of photolytic activation of PMS.

Microbial inactivations with hydrolysed lactoferrin and other natural antimicrobials in fresh-cut fennel

Natural antimicrobials (nisin, lactoferrin, thymol and citrus extract) were studied as sustainable alternatives to conventionally used NaOCl in fresh-cut (FC) fennel. Enterobacteriaceae was the most sensitive microbial group to studied sanitizers according to δ values, while psychrophiles were the most resistant. Based on inactivation modelling and sensory scores, nisin (N-250; 0.250 g L−1), lactoferrin (L-50; 50 g L−1), together with hydrolysed L-50 (LFH), were selected and studied comparing to water-washed (CTRL) and NaOCl (150 mg NaOCl L−1) on FC fennel. LFH achieved the highest psychrophilic reduction of 2.5 log units. Although NaOCl achieved the highest mesophilic, Enterobacteriaceae, lactobacilli and yeasts and moulds reductions of 1.7, 1.0, <1.7 and 1.6, respectively, N-250 still achieved 0.50–1.0 log unit reductions compared to CTRL. Conclusively, LFH and N-250 are natural antimicrobial treatments with good microbial inactivation rates which may be a good alternative to conventional NaOCl used by the FC industry.

Effect of pulsed electric fields (PEF) combined with natural antimicrobial by-products against S. Typhimurium

Abstract The effect against Salmonella enterica serovar Typhimurium of PEF treatment combined with cauliflower and mandarin by-product infusions at several concentrations (0, 1, 5, and 10% (w/v)) was evaluated at various incubation temperatures (10, 22, and 37 °C). The possible synergistic antimicrobial action of the combined process of Pulsed Electric Field (PEF) technology followed by exposure to the by-product infusions and the occurrence of sublethal cellular damage were also studied. Antimicrobial kinetics of by-product infusions alone or following PEF treatment were fitted to a Weibull model. Both mandarin and cauliflower by-product infusions showed a maximum antimicrobial effect against S. Typhimurium after 10 h at 37 °C when the microorganism was exposed to 10% of by-product infusion, achieving reductions of initial bacterial load up to undetectable levels. The effect of the PEF treatment (20 kV–900 μs) caused a reduction of 4 log cycles of the initial cell population (108 cfu/mL) of S. Typhimurium and 1 log cycle (90%) of cellular damage. Moreover, when the PEF pre-treated S. Typhimurium population was subjected to subsequent incubation in the presence of both by-product [10%] infusions, the microbial inactivation was faster, achieving a reduction of the initial bacterial load (4 log10 cycles) up to undetectable levels in 2 h. The kinetic values of the Weibull model were obtained. The higher the concentration of by-product infusion, temperature, and PEF treatment applied, the greater the kinetic parameter “b” values, which are related to the microbial inactivation rate. Therefore, the addition of cauliflower and mandarin by-product infusions could be a good additional control measure contributing to ensure bacterial counts below recommended limits in pasteurized PEF products during their storage at refrigeration temperatures.

Effect of Galacto-Oligosaccharides: Maltodextrin Matrices on the Recovery of Lactobacillus plantarum after Spray-Drying.

In this work maltodextrins were added to commercial galacto-oligosaccharides (GOS) in a 1:1 ratio and their thermophysical characteristics were analyzed. GOS:MD solutions were then used as matrices during spray-drying of Lactobacillus plantarum CIDCA 83114. The obtained powders were equilibrated at different relative humidities (RH) and stored at 5 and 20°C for 12 weeks, or at 30°C for 6 weeks. The Tgs of GOS:MD matrices were about 20–30°C higher than those of GOS at RH within 11 and 52%. A linear relation between the spin-spin relaxation time (T2) and T-Tg parameter was observed for GOS:MD matrices equilibrated at 11, 22, 33, and 44% RH at 5, 20, and 30°C. Spray-drying of L. plantarum CIDCA 83114 in GOS:MD matrices allowed the recovery of 93% microorganisms. In contrast, only 64% microorganisms were recovered when no GOS were included in the dehydration medium. Survival of L. plantarum CIDCA 83114 during storage showed the best performance for bacteria stored at 5°C. In a further step, the slopes of the linear regressions provided information about the rate of microbial inactivation for each storage condition (k values). This information can be useful to calculate the shelf-life of spray-dried starters stored at different temperatures and RH. Using GOS:MD matrices as a dehydration medium enhanced the recovery of L. plantarum CIDCA 83114 after spray-drying. This strategy allowed for the first time the spray-drying stabilization of a potentially probiotic strain in the presence of GOS.

Impact of pulsed-electric field and high-voltage electrical discharges on red wine microbial stabilization and quality characteristics.

In this study, pulsed-electric fields (PEF) and high-voltage electrical discharges (HVED) are proposed as new techniques for the microbial stabilization of red wines before bottling. The efficiency of the treatment was then evaluated. PEF and HVED-treatments have been applied to wine for the inactivation of Oenococcus oeni CRBO 9304, O.oeni CRBO 0608, Pediococcus parvulus CRBO 2.6 and Brettanomyces bruxellensis CB28. Different treatment times (1, 2, 4, 6, 8 and 10ms) were used at 20kVcm(-1) for the PEF treatments and at 40kV for the HVED treatments, which correspond to applied energies from 80 to 800 kJl(-1) . The effects of the treatments on the microbial inactivation rate and on various characteristics of red wines (phenolic composition, chromatic characteristics and physico-chemical parameters) were measured. The application of PEF or HVED treatments on red wine allowed the inactivation of alteration yeasts (B.bruxellensis CB28) and bacteria (O.oeni CRBO 9304, O.oeni CRBO 0608 and P.parvulus CRBO 2.6). The electric discharges at 40 kV were less effective than the PEF even after 10ms of treatments. Indeed, 4ms of PEF treatment at 20kVcm(-1) were sufficient to inactivate all micro-organisms present in the wines. Also, the use of PEF had no negative impact on the composition of wines compared to the HVED treatments. Contrary to PEF, the phenolics compounds were degraded after the HVED treatment and the physico-chemical composition of wine were modified with HVED. PEF technology seems to be an interesting alternative to stabilize microbiologically wines before bottling and without modifying their composition. This process offers many advantages for winemakers: no chemical inputs, low energy consumption (320kJl(-1) ), fast (treatment time of 4ms) and athermal (ΔT≈10°C).

Continuous inactivation of alkaline phosphatase and Escherichia coli in milk using compressed carbon dioxide as inactivating agent

This work investigated a continuous processing of milk for inactivation of alkaline phosphatase and Escherichia coli ATCC 25922 using supercritical carbon dioxide as inactivating agent. For this purpose, the influence of CO2 to milk mass ratio in the range of 0.05–0.45wt%, temperature from 30 to 70°C, pressure from 80 to 180 bar and apparent residence time from 10 to 30min on the enzyme and microbial inactivation were investigated by means of a central composite design for three independent variable. Enzyme inactivation of 94.5% was reached when the process was operated at CO2 to milk mass ratio of 0.05, 70°C, 80 bar and apparent residence time of 30min. At this condition, the rate of microbial inactivation was 0.09min−1. Results presented in this work contribute for the development of innovative process for food processing and preservation. The continuous operation consists in an advance in the use of supercritical carbon dioxide for food treatment.

High-Power Ultrasound Assisted High-Pressure Carbon Dioxide Pasteurization of Fresh-Cut Coconut: a Microbial and Physicochemical Study

A combined treatment based on high-pressure carbon dioxide and high-power ultrasound (HPCD + HPU) technologies was investigated for the pasteurization of fresh-cut coconut. Inactivation kinetics of both the natural microbiota and Salmonella enterica typhimurium spiked on the product were determined at 12 MPa and 10 W, delivered every 2 min of treatment, as a function of temperature (from 24 to 50 °C) and treatment time (from 5 up to 30 min). Additionally, to study the effect of HPCD + HPU on the quality of the product, physicochemical attributes (total acidity, pH, color, texture, dry matter, fat content, enzymatic activity, antioxidant capacity, phenols, flavonoids, and phenolic acids) were measured after the combined treatment and during a refrigerated shelf life of 4 weeks. The results revealed that HPCD + HPU increased microbial inactivation rates compared with HPCD alone: 8 log reductions of S. typhimurium were achieved with HPCD + HPU at 12 MPa, 40 °C, 20 min, while just a 4 log reduction was achieved with HPCD alone. Similar results were obtained for the natural microbiota; milder conditions of temperature and pressure were sufficient to assure inactivation to undetectable levels even of mesophilic microorganisms, the most resistant ones. Total acidity and pH did not change after the combined treatment and during the entire storage of 4 weeks, while slight differences were observed for the other physicochemical parameters. Overall, the results showed the feasibility and the potential of HPCD + HPU as an innovative non-thermal technology for the pasteurization of fresh-cut fruits.