Effects of High‐Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters

The purpose of the study was to determine the effect of high‐hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin‐conjugated magnetic beads (PGM‐MBs) and viral RNA was quantified by real‐time RT‐PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log₁₀ reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1‐ to 5‐scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure‐treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05).     

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.     

Inactivation of hepatitis A virus,poliovirus and a norovirus surrogate by high pressure processing

Hepatitis A virus (HAV), feline calicivirus (FCV, a surrogate for non-culturable norovirus), and poliovirus (PV), suspended in buffered cell culture media, were treated with pressures ranging from 200 to 600 MPa at ambient temperature for between 30 and 600 s. HAV was inactivated by > 1-log₁₀ tissue culture infectious dose 50% mL^− 1 (TCID₅₀ mL^− 1) and > 2-log₁₀ TCID₅₀ mL^− 1 after 600 s treatment with 300 and 400 MPa, respectively, and was undetectable (> 3.5-log₁₀ TCID₅₀ mL^− 1 reduction) within 300 s treatment with 500 MPa. FCV was inactivated by 3.6-log₁₀ TCID₅₀ mL^− 1 after 120 s treatment with 300 MPa, and was undetectable after 180 s treatment with 300 MPa. PV was the most resistant with little or no substantial reduction in titre after 300 s treatment with 600 MPa. The studies were designed to determine the efficacy of using high pressure to inactivate enteric viruses and generate inactivation data to assist in determining appropriate process criteria for safe shellfish production.Industrial relevanceThe high pressure treatment of raw oysters has proved commercially successful, due in part to a marked increase in the product’s shelf life, yet little alteration of its organoleptic properties. Illnesses from human enteric viruses such as hepatitis A virus and norovirus have traditionally been associated with shellfish consumption, and for this reason, studies have examined the stability of enteric viruses under high pressure. However, kinetic data on enteric virus stability under pressure is needed by processors to better understand the response of viruses throughout the entire treatment time. The kinetic data obtained in this study may be useful for processors wishing to alter high pressure processing conditions to ensure a high quality product in terms of organoleptic and microbiological properties.     

Comparison of the murine norovirus-1 inactivation in cabbage Kimchi with two different salinities during storage

Enteric noroviruses are occasionally detected in Kimchi, which is a traditional dish made of fermented vegetables. This study was aimed at examining the effects of two levels of salt concentrations on the survival of murine norovirus-1 (MNV-1), a human norovirus surrogate, in experimentally contaminated cabbage Kimchi stored at 5 °C for 10 weeks. The number of total aerobic bacteria (TAB) and lactic acid bacteria (LAB), MNV-1 titer pH, and acidity were measured every week. The titers of MNV-1 in both low (1.17%) and normal (2.22%) salinity cabbage Kimchi were significantly (P < 0.05) decreased with increase in storage time. The overall reduction was 1.75 log₁₀ plaque-forming unit (PFU)/mL in normal salinity cabbage Kimchi and 1.24 log₁₀ PFU/mL in low salinity cabbage Kimchi. The time required to reduce the titer by > 1 log₁₀ PFU/mL in normal and low salinity cabbage Kimchi were 4 and 8 weeks, respectively. The pH value under both salinities significantly (P < 0.05) decreased until 4 weeks. The maximum acidity was 0.83% and 0.79% in normal and low salinity cabbage Kimchi, respectively, during the 10 weeks. The population of TAB and LAB reached up to 7.33 log₁₀ colony-forming unit (CFU)/g as a maximum population during the storage period of 3 weeks in normal salinity cabbage Kimchi. However, the population of TAB and LAB in low salinity cabbage Kimchi reached to 6.99 and 7.04 log₁₀ CFU/g at 5 and 4 weeks, respectively. Through these findings, fermentation factors such as TAB, LAB, pH, and acidity of cabbage Kimchi were influenced by salt concentration. The inactivation of MNV-1 in normal salinity cabbage Kimchi was much faster than that in low salinity cabbage Kimchi because the fermentation in normal salinity cabbage Kimchi progressed more quickly than that in low salinity cabbage Kimchi. However, both salinity cabbage Kimchi were able to infect cells for 70 days even though the MNV-1 was reduced over 1 log₁₀ during fermentation. Therefore, the way to protect cabbage Kimchi from norovirus must be considered.     

Inactivation of Escherichia coli O157:H7, Salmonella and human norovirus surrogate on artificially contaminated strawberries and raspberries by water-assisted pulsed light treatment

This study investigated the inactivation of Escherichia coli O157:H7, Salmonella and murine norovirus (MNV-1), a human norovirus surrogate, on strawberries and raspberries using a water-assisted pulsed light (WPL) treatment. The effects of combinations of WPL treatment with 1% hydrogen peroxide (H₂O₂) or 100 ppm sodium dodecyl sulfate (SDS) were also evaluated. Strawberries and raspberries were inoculated with E. coli O157:H7 and treated by WPL for 5–60 s. E. coli O157:H7 on both strawberries and raspberries was significantly reduced in a time-dependent manner with 60-s WPL treatments reducing E. coli O157:H7 by 2.4 and 4.5 log CFU/g, respectively. Significantly higher reductions of E. coli O157:H7 were obtained using 60-s WPL treatment than washing with 10 ppm chlorine. Compared with washing with chlorine, SDS and H₂O₂, the combination of WPL treatment with 1% H₂O₂ for 60 s showed significantly higher efficacy by reducing E. coli O157:H7 on strawberries and raspberries by 3.3- and 5.3-log units, respectively. Similarly, Salmonella on strawberries and raspberries was inactivated by 2.8- and 4.9-log units after 60-s WPL–H₂O₂ treatments. For decontamination of MNV-1, a 60-s WPL treatment reduced the viral titers on strawberries and raspberries by 1.8- and 3.6-log units, respectively and the combination of WPL and H₂O₂ did not enhance the treatment efficiency. These results demonstrated that the WPL treatment can be a promising chemical-free alternative to chlorine washing for decontamination of berries destined for fresh-cut and frozen berry products. WPL–H₂O₂ treatment was the most effective treatment in our study for decontamination of bacterial pathogens on berries, providing an enhanced degree of microbiological safety for berries.     

Inactivation of spoilage yeasts in apple juice by UV–C light and in combination with mild heat

The UV–C resistance of yeasts (Saccharomyces cerevisiae, Saccharomyces bayanus, Zygosaccharomyces bailii, Dekkera anomala and Dekkera bruxellensis) commonly involved in juice spoilage was investigated. Saccharomyces spp. showed the greatest UV resistance and yeast inactivation decreased with absorptivity of the medium. To improve the UV lethal effect on yeasts in juice, UV treatment was combined with heat (UV–H) (45–60 °C). The inactivation of S. cerevisiae by UV–H treatments between 52.5 and 57.5 °C was greater than use of both technologies individually, suggesting a synergistic effect. Modeling of inactivation data found that a combination of UV–C light with mild temperatures (50–60 °C) produced a 5-log₁₀ reduction of S. cerevisiae in clarified apple juice with lower UV doses (up to a 89.3% of reduction at 57.5 °C) and treatment times (up to 63% of reduction at 52.5 °C) than those needed for UV treatments or heat alone.Industrial relevanceThis investigation demonstrated the lethal efficacy of the combination of UV–C radiation and heat to improve the inactivation of spoilage yeasts in juice. Combined UV–H treatments synergistically increased yeast inactivation, with this approach being less effective than for bacteria. In any case, UV–H at mild temperatures would be an alternative to heat pasteurization treatments, enabling the inactivation of pathogenic bacteria and reducing the concentration of spoilage microorganisms like yeasts, obtaining a safe and stable product at lower temperatures.     

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure

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 (log₁₀ 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 (log₁₀ 1.27 for FDA and log₁₀ 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 log₁₀ 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).     

Moisture sorption isotherms of high pressure treated fruit peels used as dietary fiber sources

High hydrostatic pressure (HHP) treatments can improve the potential of orange, mango, and prickly pear peels as food formulation fiber sources. Akaike Information Criteria differences identified Peleg and GAB as the best model alternatives to describe experimental moisture isotherms. HHP (600 MPa/10 min/22 and 55 °C) effects on moisture isotherms expressed as relative water sorption content change with respect to controls (RWSC_aw) showed that in the 0.1–0.93 a_w range, HHP improved the adsorption water retention of orange peels. The same was true for the desorption water retention for all HHP-treated fruit peels except for prickly pear HHP-treated at 22 °C and > 0.35 a_w. The area under the hysteresis curve (A_H) in the 0.15–0.51 a_w range showed that HHP increased hysteresis for all fruit peels tested. All this illustrates the HHP potential to modify the hygroscopic properties of fruit peels at lower temperature and in less processing time than conventional processes.Industrial relevanceOrange, mango, and prickly pear peels are potential food fiber formulation sources with differentiated hygroscopic and functional properties. In this study, 600 MPa treatments at 22 and 55 °C for 10 min modified the adsorption and desorption moisture retention capacity of all fruit peels tested in this study. HHP technology can improve the potential of fruit peels as dietary fiber sources with the advantage of shorter processing times and lower temperatures than conventional technologies used to treat food fibers.     

Reuterin,lactoperoxidase, lactoferrin and high hydrostatic pressure treatments on the characteristics of cooked ham

The effect of reuterin, lactoperoxidase system (LPS) and lactoferrin (LF) combined with high hydrostatic pressure (HHP) on the characteristics of sliced cooked ham during 35 days at 4 and 10 °C were investigated. Reuterin and LPS inhibited the growth of total microorganisms during 35 days at 4 and 10 °C, whereas a regrowth at 10 °C was observed when HHP was applied. Combined treatments kept total viable counts below 1.5 log cfu/g after 35 days at 10 °C. Regarding the effect of treatments on colour of cooked ham, LPS alone or in combination with HHP slightly affected L*, a* and b* values, but these changes tended to attenuate during storage. Likely, slight differences were registered in shear strength values among control and treated cooked ham. The accumulation of volatile compounds was reduced in cooked ham treated with LPS and LF in combination with HHP, even under abuse temperature conditions (10 °C).Industrial relevanceLPS applied in combination with HHP was the most effective treatment at reducing the growth of total microorganisms in refrigerated cooked ham with minor changes in its characteristics. The antimicrobial activity of such combined treatment against food-borne pathogens, which has also been reported in RTE foods, points to its usefulness to assure a safe product of sensory characteristics similar to those of untreated cooked ham.     

The effect of high hydrostatic pressure on the microbiological quality and physical–chemical characteristics of Pumpkin (Cucurbita maxima Duch.) during refrigerated storage

Pumpkins were processed at high hydrostatic pressure (HHP) ranging from 350 to 550 MPa for 0.5 min to 30 min. Two different nonlinear mathematical models were compared to fit the inactivation kinetics. The second model consistently produced better fits to the inactivation data than the first model (Weibull model). According to the inactivation of microorganisms, pumpkin was subjected to 450 MPa/15 min and 550 MPa/10 min. The microbiological and physicochemical changes in pumpkin subjected to (HHP) and thermal-treated (854 °C/5 min) were compared during 4 °C storage. The total plate counts (TPC) treated with thermal processing, 450 MPa/15 min and 550 MPa/10 min were 5.12, 4.02 and 1.71 log₁₀ CFU/g, respectively on the 60th day. The growth of microorganisms caused the increase in ΔE, decrease in hardness in other treatments. Treatment of 550 MPa for 10 min had little effect on color during storage. There were no significant changes in the L^⁎, a^⁎ and b^⁎ values (p > 0.05). The hardness of pumpkin treated with 550 MPa/10 min decreased by 32.28% after 60 days. A greater retention of the original color, Vc and antioxidant capacity and increased total phenols were observed in 550 MPa/10 min-treated samples immediately after processing. During storage, color changed, Vc content, total phenols and the antioxidant activity were decreased. While the soluble solids content (SSC), sugars and pH value of pumpkin with HHP or thermal treatment did not show significant change immediately during 60-day storage. Based on these results, working at 550 MPa for 10 min ensures physicochemical and high standard of sanitation parameters in pumpkin.Industrial relevancePumpkin (Cucurbita maxima Duch.) is one of the popular vegetables, and fresh-cut pumpkin requires strict processing treatment and storage conditions to protect its quality. HHP is one promising novel non-thermal technique and is likely to replace thermal processes. A better knowledge of effects of storage temperature on the quality of HHP-treated pumpkin and its storage time prediction through microbiological quality and physical–chemical characteristics analysis of these changes is necessary. The available data would provide technical support for commercial application of the HHP technique in fresh-cut pumpkin processing.     

Effects of high hydrostatic pressure on physicochemical properties,enzymes activity,and antioxidant capacities of anthocyanins extracts of wild Lonicera caerulea berry

Wild Lonicera caerulea berries were subjected to five different high hydrostatic pressure (HHP) treatments (which resemble the conditions of active component extraction and commercial sterilization). The content of anthocyanins and total phenolics increased by 6.84% and 14.35% (p < 0.05), respectively after treatment at 200 MPa for 5 and 10 min. As HHP increased, a higher loss of active component was observed. The total phenolic contents did not differ significantly between the control and the 400 MPa/20 min treated group (p > 0.05); HHP processing demonstrated better sterilization effect but severely destroyed enzymes. Polyphenol oxidase (PPO) and peroxidase (POD) activity were activated at lower HHP, such as 200 MPa, and decreased at 400–600 MPa. Superoxide dismutase (SOD) maintained good stability under HHP processing. The antioxidant capacities of anthocyanins extracts of wild L. caerulea berry were evaluated by 3 different methods (DPPH assay, oxygen radical absorbance capacity assay, and cellular antioxidant activity assay).Industrial RelevanceFactors such as color, luster, and nutrition often affect consumer choice in food. However, the color and nutrition of foods tend to be destroyed during processing and storage. The demand for healthier and more nutritious food while retaining the color and flavor after processing highlights the need to develop novel and gentler technologies for fruit processing. Recently, high hydrostatic pressure (HHP) technologies have been used in different branches of the food industry. In the present study, the content of active component in blue honeysuckle fruit pulps such as anthocyanins and polyphenols showed tendency to increase and then decrease with increasing pressure at room temperature. Five different HHP treatment groups (resembling the conditions of active component extraction conditions and commercial sterilization) were compared to the control (fresh fruit) and heat-treated group to determine the effects of HHP processing on L. caerulea berry pulps. The aim of this study was to investigate the changes in active component particularly the content and composition of anthocyanins under different high-pressure treatment at room temperature; the color and physicochemical indexes were also analyzed at the same conditions. Low HHP for a long period of time (400 MPa/20 min) demonstrated better results than that with high HHP for a short time (600 MPa/10 min), as indicated by the higher contents of anthocyanins and phenols and stronger antioxidant capacities. Therefore, Low HHP conditions can be used as an auxiliary means of active component extraction. The conditions of HHP processing at low HHP for a long period of time (400 MPa/20 min) can be altered to retain active components during food processing.     

Okara treated with high hydrostatic pressure assisted by Ultraflo® L: Effect on solubility of dietary fibre

Okara is an abundant and inexpensive by-product from soybean, rich in total dietary fibre (> 55% dry weight), but poor in soluble dietary fibre (SDF, < 5% dw). A combined method of high hydrostatic pressure (HHP) aided by the food grade enzyme Ultraflo® L was used for SDF maximization. At atmospheric pressure, incubation time was not a key factor, and a ratio of 1:40 (enzyme:Okara, v/w) was able to saturate the enzyme within 120–150 min. When HHP plus Ultraflo® L were applied, a synergy between both treatments was observed. Thus, at 600 MPa, 0.025% Ultraflo® L and 30 min treatment, soluble carbohydrate added up to 15.64 ± 0.32%, consisting of two peaks (9.14 ± 0.18 and 0.57 ± 0.01 kDa), determined by HPLC-ELSD. The combination of HHP plus Ultraflo® L on Okara improved the solubility of the dietary fibre, making it more suitable to be used in functional foods.Industrial relevanceThere is an increasing interest in finding new prebiotics from food industrial waste. Okara has been simultaneously treated with Ultraflo® L and HHP, taking into account the industrial costs of the procedure, and adjusting the quantity of enzyme and time of treatment to the minimum, by a Response Surface Methodology and an enzymatic activity assay. Besides, an HPLC-ELSD direct analysis (High Performance Liquid Chromatography with Evaporative Light Scattering Detector) was employed to monitor soluble fibre, as an easy and fast analytical method.     

Effects of high-pressure and heat treatments on physical and biochemical characteristics of oysters (Crassostrea gigas)

Physical and biochemical changes in oysters following high-pressure (HP) treatment at 260 MPa for 3 min or heat treatment (cool pasteurisation (CP) at 50 °C for 10 min or traditional pasteurisation (TP) at 75 °C for 8 min) were investigated and compared to changes in untreated oysters. HP or TP oysters had higher (P < 0.05) pH values (6.49–6.58) than untreated or CP oysters (6.45–6.46). HP and heat treatment both modified the gross composition of oyster tissue. The protein content of HP-treated oysters (6.9%) was significantly (P < 0.05) lower compared to control or heat-treated oysters (7.9–9.1%). The moisture content of HP-treated whole oyster tissue (86.5%) was higher than that of heat-treated or untreated oysters (83.5–84.7%), but HP or CP treatments did not affect the salt content or water activity of oysters. However, all treatments increased Hunter L- (66.3–68.9) while decreasing a- (− 1.6 to − 2.4) and b- (15.8–14.5) values of oyster tissue; overall, HP treatment had less negative effects on tissue colour of oysters than thermal treatments. HP-treated, CP and TP oysters had higher shucking yields (15.5%, 12.5% and 2.6%, respectively) than untreated oysters. One significant advantage of HP treatment over heat treatment of oysters was that the former process opened the oyster and separated the muscle of the oyster from the shell.     

Microbial inactivation of E. coli cells by a combined PEF–HPCD treatment in a continuous flow system

A laboratory scale continuous flow unit was set up and used to study the effect of pulsed electric fields (PEF) pre-treatments on microbial inactivation by high pressure carbon dioxide (HPCD) processing with the aim of investigating the synergistic effect of the combined treatment. McIlvaine buffer solution inoculated with Escherichia coli cells ATCC26 was pre-treated with PEF (25 °C) at different field strength (E = 6–12 kV/cm) and energy input (W_T = 10–40 J/mL) and then processed with HPCD (25 °C) at pressures of 8.0, 14.0 and 20.0 MPa and holding times of 4, 7 and 11 min.Results showed that treating the microbial suspension only with PEF, the inactivation level slightly increased with increasing the field strength and energy input with no significant effect of the pressure applied. The maximum inactivation level obtained was 2.25 Log-cycles at 12 kV/cm and 40 J/mL. When the bacterial cells were treated only with HPCD, the inactivation level was almost independent on the pressure of CO₂, and gradually increased with increasing the holding time up to a maximum value of 2.41 Log-cycles. The combination of PEF and HPCD treatment resulted in a marked increase of the microbial inactivation with increasing the field strength, energy input, holding time and operative pressure. A clear synergistic effect was evident when holding time was longer than 4 min, regardless the intensity of the PEF treatment applied.Industrial relevanceConsumers demand for fresh and natural products forces food manufacturers to investigate milder preservation processes and stimulate the current trend to use hurdle technologies. Pulsed electric field (PEF) and high pressure carbon dioxide (HPCD) are emerging non-thermal technologies which have antimicrobial capabilities when applied alone or in combination with other physicochemical hurdles. The present work demonstrated, for the first time, the feasibility of combined PEF-HCPD process based on the coupling of a PEF pretreatment stage to HPCD treatment in a continuous flow unit. The results support the view that the combined process is able to induce substantial microbial inactivation at mild treatment conditions and at room temperature suggesting the idea that this process could be applied to foods with thermosensitive components.     

Nano-TiO2 particles and high hydrostatic pressure treatment for improving functionality of polyvinyl alcohol and chitosan composite films and nano-TiO2 migration from film matrix in food simulants

This study investigated the impact of nano-TiO₂ and high hydrostatic pressure (HHP) treatment on microstructure, water vapor and gas barrier, antibacterial and mechanical properties of polyvinyl alcohol (PVA)–chitosan (CHI) biodegradable films and determined the migration behavior of TiO₂ nanoparticles from the films to food simulants. Apart from the effect of filler, TiO₂ nanoparticles also could improve the antibacterial activity of the films and play a role as a plasticizer in the films. HHP treatment promoted the interaction between PVA and chitosan molecules, resulting in the formation of more compacted network structures in PVA–CHI films. The migration of TiO₂ from the films was investigated in food simulants including distilled water, acetic acid, ethanol and olive oil, in which the trace amount of TiO₂ (< 4.20 × 10^− 3‰) was only detected in olive oil. HHP treatment at 200–400 MPa significantly reduced migration of TiO₂ nanoparticles from the films.Industrial relevanceResults from this study provide a new application direction of high hydrostatic pressure (HHP) in the field of food packaging materials for improving the functionality of materials. Due to the non-thermal characteristic, HHP in combination with nano-TiO₂ not only improved the mechanical and barrier properties of the biodegradable PVA–CHI composite films (polyvinyl alcohol and chitosan based materials), but also enhanced the antibacterial activity of the films. The HHP treated PVA–CHI–TiO₂ films are very stable in food simulants, such as olive oils. Therefore, the utilization of HHP and nano-TiO₂ is promising in the preparation of food packaging materials with desirable functionalities.     

Effect of high hydrostatic pressure on the viability of Streptococcus thermophilus bacteriophages isolated from cheese

The effect of high hydrostatic pressure (HHP) on the inactivation of Streptococcus thermophilus bacteriophages ϕAbc2, ALQ13.2 and DT1 was investigated. Reductions in viability were proportional to pressure (400–600 MPa) and holding time (0–30 min), though the inactivation extent was phage-dependent. HHP treatment at 600 MPa for less than 5 min was sufficient to completely inactivate phages ϕAbc2 and DT1. However, ALQ13.2 only suffered a 3.7-log reduction which showed markedly higher resistance than ϕAbc2 and DT1. Weibull model was applied to describe the inactivation behavior of phages. Regression coefficients (R²), root mean square error (RMSE) and residual plots strongly suggested that Weibull model had a good fit to the data. Additionally, the Weibull models were simplified with a binary model since b values had a linear relationship at 400–600 MPa. The simplified Weibull model provided reasonable predictions of survival data at different pressures for ϕAbc2 and DT1.Industrial relevancePhage infection remains today the most serious and common problem in the manufacture of fermented cheese products. In particular, some S. thermophilus bacteriophages exhibited high thermal resistance, high burst size values and remarkably short latent periods. The use of alternative preservation techniques such as high hydrostatic pressure processing is an efficient method to improve cheese quality and achieve bacteriophages safety. The results showed HHP treatment was capable for complete inactivation of S. thermophilus bacteriophages. The lethal kinetics of S. thermophilus bacteriophages using the Weibull model could help the application of HHP in cheese-making industry.     

The effects of high hydrostatic pressure at subzero temperature on the quality of ready-to-eat cured beef carpaccio

We compared the application of high hydrostatic pressure (HHP) on unfrozen carpaccio (HHP at 20 °C) and on previously-frozen carpaccio (HHP at − 30 °C). HHP at 20 °C changed the color. The pressure increase from 400 to 650 MPa and the time increment from 1 to 5 min at 400 MPa increased L* and b*. a* decreased only with 650 MPa for 5 min at 20 °C. The prior freezing of the carpaccio and the HHP at − 30 °C minimized the effect of the HHP on the color and did not change the shear force, but increased expressible moisture as compared to the untreated carpaccio. HHP at 20 °C was more effective in reducing the counts of microorganisms (aerobic total count at 30 °C, Enterobacteriaceae, psychrotrophs viable at 6.5 °C and lactic acid bacteria) than HHP at − 30 º C. With HHP at 20 °C, we observed a significant effect of pressure and time on the reduction of the counts.     

Effects of high hydrostatic pressure and high-temperature short-time on mango nectars: Changes in microorganisms,acid invertase, 5-hydroxymethylfurfural,sugars, viscosity,and cloud

High hydrostatic pressure (HHP, 600 MPa/1 min) and high-temperature short-time (HTST, 110 °C/8.6 s) treatments of mango nectars were comparatively evaluated by examining their effects on natural microorganisms, acid invertase, 5-hydroxymethylfurfural (HMF), sugars, pH, titratable acid (TA), viscosity, and cloud, immediately after treatments and during 16-week storage at 4 and 25 °C. At both stages of the experiment, the counts of yeast and mold in treated mango nectars were less than 1.00 log₁₀CFU/mL, while total aerobic bacteria were less than 1.70 log₁₀CFU/mL. Both HHP and HTST treatments caused a significant decrease in fructose, glucose and total sugar, as well as a significant increase in HMF and cloud of mango nectars, while changes in sucrose, pH, and TA were insignificant. During the 16-week storage, however, fructose, glucose, TA and HMF increased, while sucrose, total sugar, pH and cloud decreased significantly. The kinetic data of changes in sucrose, fructose and glucose fitted well into a combined model. The activity of acid invertase was reduced by 91.4% in HTST-treated mango nectars and, increased by 8.57% after HHP treatment. In both cases, these levels remained stable during storage. There was no significant change in the viscosity of mango nectars after HHP treatment, while a significant increase after HTST treatment. Both HHP- and HTST-treated mango nectars showed a gradual decrease in the viscosity during storage.Industrial relevanceMango (Mangifera indica L.) is one of the important tropical fruits, and its processed products are of high commercial and economic importance. This work presents a comparison on HHP- and HTST-treated mango nectars after processing and during storage, on natural microorganisms, acid invertase, 5-hydroxymethylfurfural, sugars, pH, titratable acid, viscosity, and cloud. The available data would provide technical support for the evaluation and application of HHP or HTST in the mango nectar industry, and also for the establishment of criteria for commercial production of high quality mango nectars with safety requirements.     

Comparison of the effect of pulsed electric field or high voltage electrical discharge for the control of sweet white must fermentation process with the conventional addition of sulfur dioxide

The present work discusses the efficiency of pulsed electrical treatments for the inactivation of yeasts. The application of pulsed electric fields (PEFs) and high voltage electrical discharges (HVEDs) as alternatives to sulfites, which are used as anti-microbial to stop the fermentation of sweet white wine, was investigated. The influence of sulfite concentration (from 0 mg·L^− 1 to 500 mg·L^− 1), PEF (from 4 kV·cm^− 1 to 20 kV·cm^− 1; from 0.25 ms to 6 ms) and HVED (40 kV/cm; 1 ms or 4 ms) treatments on the inactivation of total yeasts and non-Saccharomyces yeasts was determined. The addition of SO₂ (250 mg·L^− 1) resulted in 8 log total yeast reduction. The maximum yeast inactivation obtained with PEF and HVED was respectively 3 and 4 logs. The use of SO₂, HVED and PEF allows decreasing the non-Saccharomyces yeast level by 7, 5 and 4 logs respectively. However, the wine browning was less pronounced for the samples treated by PEF in comparison with HVED and SO₂ treatments. PEF seems to be the most suitable alternative technique to sulfite addition.     

High hydrostatic pressure aided by food-grade enzymes as a novel approach for Okara valorization

Okara is a cheap, abundant and valuable by-product from soybean but it needs an easy industrial method to maximize its soluble dietary fibre (SDF) content. A novel combination of high hydrostatic pressure (HHP) assisted by the food-grade enzyme Viscozyme® L was simultaneously used for this purpose. Viscozyme® L (0.025%) was able to degrade Okara at atmospheric pressure in 120–180 min, and the most effective conditions were found at pH 7 and 37 °C (9.3% SDF). Synergy between HHP and Viscozyme® L was observed, in terms of SDF release and molecular weight decrease, as determined by direct High Performance Liquid Chromatography - Evaporative Light Scattering Detector analysis (HPLC-ELSD). In fact, at 600 MPa, 0.025% Viscozyme® L and 30 min treatment, SDF and polysaccharides content were 2.50 and 3.20-times higher than in native Okara, achieving a concentration of 13.53 ± 0.30% (SDF), which improved its nutritional value and applicability in functional foods.Industrial relevanceHHP is a novel technological process which is useful for increasing the added value of by-products like Okara by solubilizing their dietary fibre. Some enzymes increase their activity when they are under HHP. A simultaneous method with Viscozyme® L and HHP on Okara has been optimized for reducing the industrial cost of the process.