High Hydrostatic Pressure Processing Research Articles

High‐pressure processing at increased temperatures provides enhanced removal of indigenous microbial contamination in beet/carrot juice without damaging the bioactive components

SummaryIn this study, an optimised high hydrostatic pressure process (600 MPa, 15 min, 55 and 65 °C) caused elimination of microbial levels in beetroot/carrot juice (80:20 v/v, pH 4.0) after 28 days of storage (4 °C) (psychrotrophic bacteria, yeast and mould counts below the limit of detection = 0 log cfu mL−1). Room temperature (20 °C) was insufficient for the complete elimination of psychrotrophic bacteria (0.9–2.0 log cfu mL−1 after 7–28 days of storage). No significant (P < 0.05) changes in the polyphenol content were observed (1.11 ± 0.13 in control vs. 1.13 ± 0.13 mg gallic acid mL−1 in samples treated at 65 °C). No significant (P < 0.05) changes in the antioxidant, antiradical activity and biological properties of the high‐pressure processing (HPP)‐treated juice were observed in the studies involving CCD 841 CoTr and HT29 cell lines. The HPLC‐MS analysis confirmed increase in isobetalain, decarboxybetalain and betalain content (by 100%, 14% and 10%) and loss of vulgaxanthin I (by 65%) after HPP at 65 °C. The innovative character of this paper stems from the comprehensive quality assessment (especially experiments involving cell lines) of high‐quality, safe beetroot–carrot juice that retains a major part of its bioactive compounds.

Effect of High Hydrostatic Pressure on the Extractability and Bioaccessibility of Carotenoids and Their Esters from Papaya (Carica papaya L.) and Its Impact on Tissue Microstructure.

High hydrostatic pressure (HHP) is a non-thermal technology widely used in the industry to extend food shelf-life and it has been proven to enhance the extractability of secondary metabolites, such as carotenoids, in plant foods. In this study, fresh-cut papaya pulp of varieties (Sweet Mary, Alicia and Eksotika) from the Canary Islands (Spain) were submitted to the HHP process (pressure: 100, 350 and 600 MPa; time: come-up time (CUT) and 5 min) to evaluate, for the first time, individual carotenoid and carotenoid ester extractability and to assess their bioaccessibility using an in vitro simulated gastrointestinal digestion assay, following the standardized INFOGEST® methodology. In addition, changes in papaya pulp microstructure after HHP treatments and during the different phases of the in vitro digestion were evaluated with optical light microscopy. HPLC-DAD (LC-MS/MS (APCI+)) analyses revealed that HHP treatments increased the carotenoid content, obtaining the highest extractability in pulp of the Sweet Mary papaya variety treated at 350 MPa during 5 min (4469 ± 124 μg/100 g fresh weight) which was an increase of 269% in respect to the HHP-untreated control sample. The highest carotenoid extraction value within each papaya variety among all HHP treatments was observed for (all-E)-lycopene, in a range of 98–1302 μg/100 g fresh weight (23–344%). Light micrographs of HHP-treated pulps showed many microstructural changes associated to carotenoid release related to the observed increase in their content. Carotenoids and carotenoid esters of papaya pulp submitted to in vitro digestion showed great stability; however, their bioaccessibility was very low due to the low content of fatty acids in papaya pulp necessary for the micellarization process. Further studies will be required to improve papaya carotenoid and carotenoid ester bioaccessibility.

Effect of High Hydrostatic Pressure Processing on the Anthocyanins Content, Antioxidant Activity, Sensorial Acceptance and Stability of Jussara (Euterpe edulis) Juice.

Jussara (Euterpe edulis) fruit is a strong candidate for exportation due to its high content of anthocyanins. However, its rapid perishability impairs its potential for further economic exploration, highlighting the relevance of producing ready-to-drink juices by applying innovative processing, such as high hydrostatic pressure (HHP). The effect of HHP (200, 350, and 500 MPa for 5, 7.5, and 10 min) on anthocyanins content and antioxidant activity (AA) by FRAP and TEAC assays, and the most effective HHP condition on overall sensory acceptance and stability of jussara juice, were investigated. While mild pressurization (200 MPa for 5 min) retained anthocyanins and AA, 82% of anthocyanins content and 46% of TEAC values were lost at the most extreme pressurization condition (500 MPa for 10 min). The addition of 12.5% sucrose was the ideal for jussara juice consumer acceptance. No significant difference was observed for overall sensory acceptance scores of unprocessed (6.7) and HHP-processed juices (6.8), both juices being well-accepted. However, pressurization was ineffective in promoting the retention of anthocyanins and AA in jussara juice stored at refrigeration temperature for 60 days, probably due to enzymatic browning.

Non-volatile and volatile metabolic profiling of tomato juice processed by high-hydrostatic-pressure and high-temperature short-time

High hydrostatic pressure (HHP) processing has become a commercial success in fruit and vegetable processing. Herein, the effects of HHP and high-temperature short-time (HTST) processing on metabolic profiling in tomato juice was evaluated by UPLC–MS/MS, HPLC, and GC–MS; a total of 425 metabolites, 14 carotenoids, and 56 volatile compounds were identified in tomato juice. HHP processing affects the composition of the juice less than HTST processing, considering 4 and 33 differential metabolites discriminated after HHP and HTST processing, respectively. The total lycopene and carotenoid contents in tomato juice increased after HHP processing, while the β-carotene and lycopene contents decreased after HTST processing. Further, more volatile compounds and higher contents of aldehydes that contribute to green aroma and lower contents of alcohols were observed after HHP and HTST processing, respectively. These findings provide a comprehensive understanding of the advantages of HHP processing on metabolite profiles in tomato juice.

Combined effects of acidification and high-pressure processing on microbial inactivation, bioactive compounds and antioxidant activity of liquorice root sherbet

High Hydrostatic Pressure Processing (HPP) has gained more attention in the fruit and vegetable industry in recent years. In this study, the optimal acidification parameters (citric acid alone and combination with ascorbic acid at the pH range 3.0 to 4.5) were determined and the effect of HPP conditions (pressures 250- 450 MPa and exposure times 1-5 min) on acidified liquorice root sherbet (ALRS) were investigated. Results showed that acidification of LRS by only citric acid had higher aroma and flavor scores. HP treatments were effective to reduce the yeast and mould (YM) count, total coliforms (TC), and inoculated pathogens (Escherichia coli ATCC 25922 and Salmonella Typhimurium ATCC 14028) in ALRS. Although acidification of LRS achieved a significant reduction in glycyrrhizic acid (GA) content, further treatment by HPP did not affect pH, the contents of total phenolic, total soluble solids, flavonoid, and GA or the antioxidant capacity of ALRS. Our results suggests that acidification and HPP treatments could be used to increase the consumer acceptability and extend the shelf life of LRS.

Physicochemical, microstructural, and antioxidant properties of skins from pomaces of five virginia-grown grape varieties and their response to high hydrostatic pressure processing

Physicochemical, microstructural, and antioxidant properties of skins from pomaces of five virginia-grown grape varieties and their response to high hydrostatic pressure processing

Effect of combined treatments of ultrasound and high hydrostatic pressure processing on the physicochemical properties, microbial quality and shelf‐life of cold brew tea

SummaryEffects of ultrasound combined with high hydrostatic pressure (HHP) on physicochemical properties,microorganisms and storage attributes of cold brew tea were investigated. HHP at 400 MPa/5 min/25 °C inactivated the total aerobic bacteria, yeast and mould in cold brewed tea prepared by static brewing (SB‐tea) at 13 h/4 °C, ultrasonic bath (UB‐tea) at 150 W/120 min/0 °C and ultrasonic pulveriser (UP‐tea) at 600 W/40 min/0 °C, ensuring their microbiological safety. The results showed that there was no significant difference in the concentration of tea polyphenols between hot brewed tea prepared by 7 min/100 °C and cold brewed tea under different preparation conditions, while the caffeine in cold brewed tea was significantly lower (P < 0.05) than that in hot brewed tea. During the storage period of 8 days, compared with the untreated group, the cold brewed tea after HHP treatment had better microbiological safety. In addition, HHP treatment constantly maintained the tea polyphenols, pH, colour, antioxidant capacity and turbidity in cold brewed tea. The untreated and HHP‐treated cold brew tea were evaluated by 20 trained volunteers. Results showed that UB‐tea was more close to SB‐tea than UP‐tea in sensory profile, while HHP seem to maintain a good sensory profile as well. Therefore, this particular combined technology of ultrasonic bath and HHP displayed considerable potential for application in the cold brew tea manufacturing industry.

Impact of high hydrostatic pressure on the stability of lytic bacteriophages cocktail Salmonelex™ towards potential application on Salmonella inactivation

This work consisted in the first comprehensive study in which the potential to exploit the Salmonella lytic bacteriophages cocktail, Salmonelex™, in association with high hydrostatic pressure (HHP) towards potential application in egg matrices decontamination was evaluated. The impact of HHP (200–600 MPa) on the bacteriophages' viability pointed out a stability in the range of 200–400 MPa. From 400 MPa onwards, the inactivation was potentiated by an increase in the pressure magnitude, being matrix dependent. Salmonelex™ possessed a prominent baroresistance, requiring 600 MPa to completely lose its infectivity. Egg yolk presented the highest baroprotective effect, followed by whole egg and egg white. Transmission electron microscopy unveiled that 500 and 600 MPa elicited a detrimental impact on the bacteriophages’ structural integrity. It was noteworthy the barotolerance (200–300 MPa) of Salmonelex™, previously exposed to different pH conditions (5.0–9.0), which proved not to undermine its infectivity. Regarding the influence of ovalbumin, lysozyme, l-α-phosphatidylcholine, palmitic and oleic acids on the mild HHP-induced inactivation of Salmonelex™, a baroprotective effect was observed, particularly conferred by those compounds comprising egg yolk. The promising results highlighted the feasibility of utilizing Salmonelex™ as an adjuvant to mild HHP processing of egg matrices.

Application of preliminary high-pressure processing for improving bioactive characteristics and reducing antigenicity of whey protein hydrolysates.

This study investigated the use of Novo Pro-D® (NPD) and Ficin (FC) as alternative proteases for the production of bioactive peptides with reduced allergenicity from whey protein concentrate (WPC). In addition, the use of high hydrostatic pressure processing as pre-treatment of WPC and its impact on the final characteristics of hydrolysates were also evaluated. NPD treatments generated hydrolysates with a 98% reduction of soluble proteins, greater in vitro antioxidant capacity, and less immunoreactivity when compared to FC ones. However, pre-treatment was an essential tool to improve WPC hydrolysis when FC was used, resulting in hydrolysates with less soluble proteins, enhanced antioxidant capacity, and less allergenicity compared with conventional hydrolysis. As for NPD, the pre-treatment of WPC improved the in vitro antioxidant capacity and resulted in a 100% reduction in immunoreactivity to β-lactoglobulin in a shorter processing time. Importantly, bioactive peptides generated by FC displayed an improved ability to induce in vitro arterial relaxation, compared with those obtained from NPD process. Therefore, this study provides innovative evidence regarding how the proteases used for production of whey hydrolysates can improve its biological effects, and discloses the use of high hydrostatic pressure combined with enzymatic hydrolysis as a promising alternative to produce hydrolysates with improved properties.

Skimmed milk structural dynamics during high hydrostatic pressure processing from in situ SAXS

Understanding the changes in milk at a nanostructural level during high-pressure (HP) treatment can provide new insights to improve the safety and functionality of dairy products. In this study, modifications of milk nanostructure during HP were studied in situ by small-angle X-ray scattering (SAXS). Skimmed milk was pressurized to 200 or 400 MPa at 25, 40 or 60 °C and held for 5 or 10 min, and the effect of single- and double-HP treatment was also investigated. In most cases, the SAXS patterns of skimmed milk are well fitted with a three-population model: a low-q micellar feature reflecting the overall micelle size (~0.002 Å−1), a small casein cluster contribution at intermediate-q (around 0.01 Å−1) and a high-q (0.08–0.1 Å−1) population of milk protein inhomogeneities. However, at 60 °C a scattering feature of colloidal calcium phosphate (CCP) which is normally only seen with neutron scattering, was observed at 0.035 Å−1. By varying the pressure, temperature, holding and depressurization times, as well as performing cycled pressure treatment, we followed the dynamic structural changes in the skimmed milk protein structure at different length scales, which depending on the processing conditions, were irreversible or reversible within the timescales investigated. Pressure and temperature of the HP process have major effects, not only on size of casein micelles, but also on “protein inhomogeneities” within their internal structure. Under HP, increasing processing time at 200 MPa induced re-association of the micelles, however, the changes in the internal structure were more pressure-dependent than time dependent.

보리를 이용한 오징어 식해의 초고압처리에 의한 품질특성 변화

The changes in the quality of squid ‘Sikhae’ prepared with barley flour by high hydrostatic pressure processing (HHP) were investigated. The pH and amino nitrogen content (Amino-N) of the squid ‘Sikhae’ prepared with barley were 6.77 and 0.18%, respectively, and those on the 15 day of storage were 4.79 and 0.31%, respectively. The volatile basic nitrogen (VBN) content of the squid ‘Sikhae’ prepared with barley flour was 60.18 mg% in the untreated sample and 20.53 mg% in the HHP-processed sample on the 10 day of storage. The L* value of the ‘Sikhae’ prepared with barley flour was found to be higher than that with millet. The total number of bacteria in the squid ‘Sikhae’ prepared with barley flour was 8.26 CFU/g in the untreated sample and 5.90 CFU/g in the HHP-processed sample on the 5 day of storage. The change in the number of lactic acid bacteria according to the storage period showed the highest value of 9.36 log CFU/g on the 15 day of storage in the HHP-processed sample of the squid ‘Sikhae’ prepared with barley. Therefore, HHP processing of the low-salt fermented squid ‘Sikhae’ prepared with barley positively affected quality with increasing storage period.

Impacts of high hydrostatic pressure processing on the structure and properties of pectin

To understand the impacts of high hydrostatic pressure (HHP) processing on the microstructure and properties of pectin, an aqueous solution of apple pectin (50 g/L) was treated at 200, 400, and 600 MPa for 30 min. The chemical structure and properties of resultant pectin were characterized and compared with those of native pectin (0.1 MPa). The contents of α-1,4-linked d-galacturonic acid and reducing sugar in pectin did not change after HHP, whereas the degree of esterification of pectin increased slightly. Fourier transform infrared spectroscopy showed that no chemical conversion of pectin occurred during HHP process. For the first time, molecular dynamics simulation revealed that the hydrophobic hydration of the methyl group dramatically improved under HHP, thereby enhancing pectin dissolution in water. In turn, this result increased the aqueous pectin solution's apparent viscosity and stability, which are very important for fruit- and vegetable-based products containing pectin.

High‐pressure processing of shalgam with respect to quality characteristics, microbial inactivation, and shelflife extension

High hydrostatic pressure (HHP) processing of traditional fermented turnip juice (shalgam) was studied with respect to quality attributes, microbial inactivation, and shelflife extension. According to Box–Behnken design, shalgam samples were processed using 3–15 min, 4–40°C, and 200–500 MPa. The optimum processing conditions involved 34.23°C, 15 min, and 500 MPa for the color intensity and tone of 3.43 and 0.69 and the numbers of viable total mold and yeast, Lactococcus lactis subsp. cremoris, and Lactobacillus paracasei of 3.09, 2.51, and 2.68 log cfu/ml, respectively. Shalgam samples processed under the optimum conditions were stored at 4 and 22°C for 90 days. The control samples at 4 and 22°C were spoiled at 60 and 45th days, respectively. The storage time rather than the HHP processing affected physical properties, organic acids, phenolic compounds, and anthocyanins of shalgam. The treatment samples had significantly lower microbial growth during the storage time. Practical applications Due to the deteriorated color, bioactive, and sensory properties, the traditional heat processing of shalgam with the addition of antimicrobial agents (such as sodium benzoate) to extend its shelflife is not desirable by consumers. Alternative processing technologies are needed to extend its shelflife with no significant changes in its important properties. Its HHP treatment appeared as a practical option that preserved its quality parameters and extended its shelflife.

Effect of High Hydrostatic Pressure Processing on Biochemical Characteristics, Bacterial Counts, and Color of the Red Claw Crayfish Cherax quadricarinatus

The effects of high hydrostatic pressure (HHP) processing at 200 MPa, 400 MPa, and 600 MPa on the proximate composition, inactivation of bacteria, and color of the red claw crayfish Cherax quadricarinatus were evaluated. High hydrostatic pressure processing resulted in complete shelling and a significant decrease in the moisture content (P < 0.05), whereas no significant differences were observed in the content of ash, crude protein, and crude lipid, except for the crude lipid content between 200 MPa and 600 MPa groups (P < 0.05). After pressurization, the Escherichia coli, Vibrio vulnificus, and Vibrio parahaemolyticus counts decreased significantly with the increase of pressure, even to an undetected level for V. vulnificus and V. parahaemolyticus at 400 and 600 MPa (P < 0.05), respectively. During 30-d storage at 4°C and –20°C, the counts of these three bacterial species increased significantly with increased storage time and temperature. After HHP processing, a* value changed substantially, whereas L* and b* values had little change for meat. The total color difference (ΔE*) suggested that the HHP-treated red claw crayfish exhibited very distinctive or substantial differences compared with fresh individuals.

High hydrostatic pressure extract of mulberry leaves ameliorates hypercholesterolemia via modulating hepatic microRNA-33 expression and AMPK activity in high cholesterol diet fed rats.

BackgroundMulberry leaf (Morus alba L.) contains multiple bioactive ingredients and has been used in the treatment of obesity, diabetes, inflammation, and atherosclerosis. High hydrostatic pressure (HHP) processing has been developed for the extraction of bioactive compounds from plants. However, the hypocholesterolemic effect of the HHP extract from mulberry leaves and its underlying mechanism have never been investigated.ObjectiveThe specific aim of the present study was to investigate the hypocholesterolemic property of a novel extract obtained from mulberry leaves under HHP in rats.DesignSprague–Dawley rats were divided into four groups and fed either a normal diet (NOR), a high cholesterol diet containing 1% cholesterol and 0.5% cholic acid (HC), an HC diet containing 0.5% mulberry leaf extract (ML), or a 1% mulberry leaf extract (MH) for 4 weeks.ResultsHigh hydrostatic pressure extract of mulberry leaves significantly reduced the HC-increased serum levels of triglyceride (TG), cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), and hepatic contents of TG and TC. The HHP extraction from mulberry leaves also increased the HC-decreased fecal TC and bile acid levels without changing body weight, food intake, liver weight, and serum activities of alanine transaminase (ALT) and aspartate transaminase (AST) (P < 0.05). The mulberry leaf extract significantly enhanced the expression of hepatic genes such as cholesterol 7 alpha-hydroxylase (CYP7A1), liver X receptor alpha (LXRα), and ATP-binding cassette transporters, ABCG5/ABCG8, involved in hepatic bile acid synthesis and cholesterol efflux (P < 0.05). In addition, the HHP extraction of mulberry leaves significantly suppressed hepatic microRNA(miR)-33 expression and increased adenosine monophosphate-activated protein kinase (AMPK) activity.ConclusionThese results suggest that the HHP extract of mulberry leaves lowers serum cholesterol levels by partially increasing hepatic bile acid synthesis and fecal cholesterol excretion through the modulation of miR-33 expression and AMPK activation in the liver.

High pressure processing of licorice drink with respect to quality characteristics, microbial inactivation, and shelf‐life extension

High hydrostatic pressure (HHP) processing of traditional licorice drink with 200–500 MPa, 3–15 min, and 4°C–40°C revealed optimum operational conditions of 500-MPa pressure, 9.90 min and 18.5°C. Shelf-life studies with the optimum HHP settings were conducted for a 25-day storage at 4°C and 22°C. Control samples at 22°C and 4°C were deteriorated on Days 2 and 7, whereas the HHP-processed samples had a shelf life of 25 days. Initial pH, L*, a*, b*, and C* values and glabridin concentration significantly decreased, but conductivity and turbidity values, total mesophilic aerobic count and total mold and yeast count significantly increased, and no significant change was observed for the initial h°, titratable acidity (TA), glycyrrhizin concentration, and sensory properties for the HHP-processed samples during shelf-life studies. Except for vanillic, caffeic, and acetic acids and miristein, no significant change was observed on phenolic compounds and organic acids. Practical applications Due to perishable nature, licorice drink has very short shelf life, and this situation restricts large-scale production and marketing. Heat processing causes degradation on physical and sensory properties of licorice drink. HHP can achieve shelf life extension of licorice drink up to 1 month without a significant adverse impact on most of the quality parameters enabling large-scale production.

A Human Milk–Based Protein Concentrate Developed for Preterm Infants Retains Bioactive Proteins and Supports Growth of Weanling Rats

BackgroundBovine milk–based protein modulars are currently available to nutrient-enrich enteral feedings; however, they have limitations for use in very-low-birth-weight infants. ObjectivesOur objectives were to develop a human milk–based protein (HMP) concentrate and to conduct a preclinical assessment of the HMP concentrate in weanling rats. MethodsAn HMP concentrate was produced from donor milk using pressure-driven membrane filtration processes and high hydrostatic pressure processing. Protein and lactoferrin concentrations and lysozyme activity were determined by Kjeldahl, HPLC, and turbidimetric assay, respectively. Male Sprague Dawley rats 24 d old (n = 30) were randomly assigned to 1 of 3 isocaloric AIN-93G diets for 4 wk containing 100% casein (control) or with 50% of the casein replaced with the HMP concentrate (treatment) or a bovine whey protein isolate (treatment). Body weight, food intake, fat mass, plasma amino acid profiles, and organ weights were measured. Data were analyzed using linear regression models. ResultsRaw donor milk contained (mean ± SD) 101 ± 6 g protein/kg and 5 ± 1 g lactoferrin/kg of milk solids. Postprocessing, protein and lactoferrin concentrations were 589 ± 3 g/kg and 29 ± 10 g/kg, respectively. Lysozyme activity was initially 209 ± 4 U/kg and increased to 959 ± 39 U/kg in the HMP concentrate. There were no statistically significant differences in body weight, food intake, fat mass, or plasma amino acid profiles between rats fed diets containing the HMP concentrate and the control diet. Full cecum weights were higher in rats fed the HMP concentrate than in those fed control diets (mean difference: 5.59 g; 95% CI: 4.50, 6.68 g; P < 0.0001), likely reflecting the concentration of human milk oligosaccharefides. No differences were found for other organ weights. ConclusionsThe HMP concentrate retained important bioactive proteins and supported normal rat growth in the preclinical assessment.

Inactivation of Bacillus cereus spores using a combined treatment of UV-TiO2 photocatalysis and high hydrostatic pressure

Bacillus cereus spores are resistant to high hydrostatic pressure (HHP) processing treatment. A combination of UV-TiO2 photocatalysis (UVTP for 10 min) and two cycles of 600 MPa HHP treatment for 10 min for the first cycle and 1 min for the second cycle (UVTP-2HHP) at ambient temperature was applied to inactivate B. cereus spores inoculated on a solidified agar matrix (SAM) used as a model matrix. Two cycles of HHP treatment were used as a strategy for induction of spore germination, followed by inactivation. UVTP and 2 cycles of HHP resulted in a 5.0-log CFU/cm2 spore reduction (initial spore count was 6.6 log CFU/cm2), including an approximate 0.8-log CFU/cm2 reduction due to a synergistic effect. The inactivation mechanism of UVTP pretreatment was related to lipid peroxidation of the spore membrane based on the level of malondialdehyde (MDA) making spores susceptible to the HHP treatment. Flow cytometry and transmission electron microscopic (TEM) analyses showed severe physiological alteration and structural damage to spores after the combined treatment. UVTP and 2 cycles of HHP showed potential for effective inactivation of B. cereus to ensure food safety from B. cereus spores on food products. Practical applicationsInactivation of bacterial spores remains a technical challenge for HHP and other interventions because spores are highly resistant to high pressure. Pretreatment with UVTP followed by two cycles of HHP resulted in reduction in B. cereus spores due to a synergistic effect. This hurdle technology of UVTP and HHP can help food industry in ensuring food safety against the Bacillus spores.

Application of supercritical fluid carbon dioxide in improving food shelf-life and safety by inactivating spores: a review.

Extending shelf-life of food, ensuring it is safe for consumers and meeting regulatory standards is the food industry's governing principle. Food safety is an essential aspect of food processing. Spores-forming microbes such as Bacillus spp. and Clostridium spp. are problematic in the food industry because of their ability to form endospores and survive processing conditions. Hence, their germination in food poses a threat to both shelf-life and safety of food. This paper reports on the current state of supercritical fluid carbon dioxide (SF-CO2) application in the inactivation of spores-forming microbes in food. Unlike high hydrostatic pressure and thermal processes which struggle to deactivate and destroy spores, and if they do, it impacts adversely on the food nutritional and quality attributes. This technique is viable to inactivate spores and maintain the foods structural and nutritional characteristics. The mechanisms of inactivation can be grouped into: (1) release of cellular content due to rupture of the cell wall, coat and cortex, and disruption of membranes, (2) degradation of proteins as a result of interaction with permeated and penetrated SF-CO2 and (3) deactivation of enzymatic activities. It was discovered that the synergistic effect of ultrasound another non-thermal technique or addition of co-solvent such as water, hydrogen peroxide and ethanol or antimicrobial peptide greatly enhanced inactivation of spores. This work harmonizes published perspectives on spores' inactivation mechanisms, and will help inform further research into the application of SF-CO2 in the sterilization of food products.

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.