High Pressure Processing Treatment Research Articles

Investigation of the formation of furfural compounds in apple products treated with pasteurization and high pressure processing

The thermal treatment carried out in the processing of apple products is very likely to induce Maillard reaction to produce furfurals, which have raised toxicological concerns. This study aimed to elucidate the formation of furfural compounds in apple products treated with pasteurization and high pressure processing (HPP). The method for simultaneous determination of five furfural compounds including 5-hydroxymethyl-2-furfural (5-HMF), furfural (F), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), 2-acetylfuran (FMC), and 5-Methyl-2-furfural (MF) using high performance liquid chromatography equipped with diode array detector (HPLC-DAD) was successfully developed and validated. All five furfurals exhibited an increasing trend after the pasteurization treatment of apple clear juice, cloudy juice, and puree. 5-HMF, F, FMC, and MF were increased significantly during the precooking of apple puree. Whereas there was no significant change in the furfurals formation after apple products treated with high pressure processing (HPP) with 300 MPa and 15 min. Based on the variation of the fructose, glucose and sucrose detected in apple products after thermal treatment, it revealed that the saccharides and thermal treatment have great effect on the furfural compounds formation. The commercial fruit juice samples with different treatments and fruit puree samples treated with pasteurization were also analyzed. Five furfurals were detected more frequently in the fruit juice samples treated with pasteurization or ultra-high temperature instantaneous sterilization (UHT) than those treated with HPP. 5-HMF and FMC were detected in all fruit puree samples treated with pasteurization, followed by F, MF, and HDMF with the detection rate of 79.31 %, 72.41 %, and 51.72 %. The results could provide a reference for risk assessment of furfural compounds and dietary guidance of fruit products for human, especially for infants and young children. Moreover, moderate HPP treatment with 300 MPa and 15 min would be a worthwhile alternative processing technology in the fruit juice and puree production to reduce the formation of furfural compounds.

High-Pressure Processing of Different Tissue Homogenates from Pigs Challenged with the African Swine Fever Virus.

African swine fever (ASF) is a disease that is a growing threat to the global swine industry. Regulations and restrictions are placed on swine movement to limit the spread of the virus. However, these are costly and time-consuming. Therefore, this study aimed to determine if high-pressure processing (HPP) sanitization techniques would be effective against the ASF virus. Here, it was hypothesized that HPP could inactivate or reduce ASF virus infectivity in tissue homogenates. To test this hypothesis, 30 aliquots of each homogenate (spleen, kidney, loin) were challenge-infected with the Turin/83 strain of ASF, at a 10 7.20 median hemadsorption dose (HAD)50/mL. Subsequently, eight aliquots of each homogenate were treated with 600 millipascal (600 MPa) HPP for 3, 5, and 7 min. Six untreated aliquots were used as the controls. Virological results showed a reduction in the viral titer of more than 7-log. These results support the validity of the study hypothesis since HPP treatment was effective in inactivating ASFV in artificially prepared samples. Overall, this study suggests the need for further investigation of other ASFV-contaminated meat products.

Enhancing filter efficiency of polyimide/polyethersulfone nanofiber membranes via novel treatments of high pressure processing, thermocompression, atmospheric plasma, and corona discharge

In this study, novel post-treatments contained of high pressure processing (HPP), thermocompression, atmospheric plasma, and corona discharge were used to progress the filter quality of polyimide/polyethersulfone (PI/PES) nanofiber membranes in the conditions of 50/50 % PI/PES, 0.15 ml/hr flow rate, 22.5 kV, and 20 min. The filter quality of nanofiber membrane did not get progress after HPP and thermocompression treatments, so high temperature and pressure did not improve the filter quality. Otherwise, atmospheric plasma destroyed the morphology of fiber surface, caused loss of filter efficiency and filter quality. However, corona discharge treatment presented different result with the above three treatments, and the filter efficiency and filter quality of the fiber membrane was improved after corona discharge treatment. Furthermore, factor influence order was ranged as operational voltage, discharge time, and discharge distance from result of filter quality on comparison of S/N value and level difference via Taguchi method. The application of corona discharge resulted in fiber acquired surface electric potential of 0.315 ± 0.56 kV at the optimized conditions of operational voltage (25 kV), discharge distance (7 cm), and discharge time (60 min), and filter efficiency of fiber enhanced from 95.66 ± 0.96 % to 98.70 ± 0.36 %. Further, the optimized PI/PES nanofiber membranes with corona discharge not only had a remarkable filter quality (2.214 Pa−1) but also maintained an effective filtration efficiency of ultra-fine particles (98.70 %) and a low pressure loss of 1.961 Pa for creating a promising filter of air purification and N95 Masks of USA NIOSH Standard.

High-pressure processing (HPP) of phycocyanin extract solutions: Enhancing stability through molecular interactions

C-Phycocyanin (PC) has been proposed as a replacement for synthetic colors in foods. However, C-PC stability is adversely affected during food processing due to exposure to high temperature, pressure, oxygen concentration or extreme pHs. This study assessed the degradation mechanisms of C-PC under a nonthermal pasteurization technology, i.e., High-Pressure Processing (HPP), and identified potential processing protocols to arrest C-PC instability at low pH. Aqueous C-PC solutions (pH:4–6) were subject to HPP (500–600 MPa) for 1–5 min. C-PC stability was monitored based on changes in the photophysical properties of its fluorophores (phycocyanobilin chromophore and aromatic amino acid residues) and particle size. pH significantly affected C-PC's stability towards HPP (<stability at < pH). Sharper hypsochromic (blue) shifts, lower intensity, and higher anisotropy were observed as pressure and treatment time increased, which suggested conformational changes in C-PC's polypeptides, followed by aggregation. pH adjustment after HPP treatments resulted in a significant reduction in color loss and aggregation, possibly due to partial stabilization of the polypeptide subunits' conformation.

Optimization of processing conditions of starch-based hydrogels produced by high-pressure processing (HPP) using response surface methodology

Introduction: This study aimed to determine the optimal processing conditions to produce stable starch-based hydrogels by high-pressure processing (HPP) via response surface methodology.Methods: The experiments were carried out with different starch suspensions, namely rice, corn, wheat, and tapioca starch, at a concentration in the range of 10%–40% w/w, processed at a pressure level of 600 MPa and holding times between 5 min and 15 min. Gel formation was assessed by determining the gelatinization extent and structuring level of the samples.Results and discussion: The results demonstrated that starch/water ratio and holding time had a significant impact on gel formation in HPP treatments. Various degrees of gelatinization were observed in the treated samples due to the water absorption capacity of the starch and the molecular interactions between water and starch occurring during gelatinization. Moreover, a highly structured hydrogel formed at starch concentrations higher than 25% (w/w), whereas when starch concentration was less than 20% (w/w) lower-structured hydrogels formed, as confirmed by the values of the efficiency index measured. Completely gelatinized, highly structured, and stable HPP hydrogels were obtained from starch solutions treated at the optimized processing conditions.

PMAxx-RT-qPCR to Determine Human Norovirus Inactivation Following High-Pressure Processing of Oysters.

Norovirus is the leading cause of viral gastroenteritis globally. While person-to-person transmission is most commonly reported route of infection, human norovirus is frequently associated with foodborne transmission, including through consumption of contaminated bivalve molluscan shellfish. Reverse transcription (RT)-qPCR is most commonly used method for detecting human norovirus detection in foods, but does not inform on its infectivity, posing challenges for assessing intervention strategies aimed at risk elimination. In this study, RT-qPCR was used in conjunction with a derivative of the photoreactive DNA binding dye propidium monoazide (PMAxx™) (PMAxx-RT-qPCR) to evaluate the viral capsid integrity ofnorovirus genogroup I and II (GI and GII) in shellfish following high pressure processing (HPP). Norovirus GI.3 and GII.4 bioaccumulated oysters were subjected to HPP at pressures of 300 and 450MPa at 15°C, and 300, 450 and 600MPa at 20°C. Samples were analysed using both RT-qPCR and PMAxx-RT-qPCR. For each sample, norovirus concentration (genome copies/g digestive tissue) determined by RT-qPCR was divided by the PMAxx-RT-qPCR concentration, giving the relative non-intact (RNI) ratio. The RNI ratio values relate to the amount of non-intact (non-infectious) viruses compared to fully intact (possible infectious) viruses. Our findings revealed an increasing RNI ratio value, indicating decreasing virus integrity, with increasing pressure and decreasing pressure. At 300MPa, for norovirus GI, the median [95% confidence interval, CI] RNI ratio values were 2.6 [1.9, 3.0] at 15°C compared to 1.1 [0.9, 1.8] at 20°C. At 450MPa, the RNI ratio values were 5.5 [2.9, 7.0] at 15°C compared to 1.3 [1.0, 1.6] at 20°C. At 600MPa, the RNI ratio value was 5.1 [2.9, 13.4] at 20°C. For norovirus GII, RT-qPCR and PMAxx-RT-qPCR detections were significantly reduced at 450 and 600MPa at both 15°C and 20°C, with the median [95% CI] RNI ratio value at 300MPa being 1.1 [0.8, 1.6]. Following HPP treatment, the use of PMAxx-RT-qPCR enables the selective detection of intact and potential infectious norovirus, enhancing our understanding of the inactivation profiles and supporting the development of more effective risk assessment strategies.

High-pressure processing enhances saltiness perception and sensory acceptability of raw but not of cooked cured pork loins-leveraging salty and umami taste.

The salt (NaCl) content in processed meats must be reduced because of its adverse effects on cardiovascular health. However, reducing salt in meat products typically leads to a lower taste intensity and, thus, consumer acceptability. Industry interventions must reduce salt content while maintaining taste, quality, and consumer acceptability. In this context, high-pressure processing (HPP) has been proposed to enhance saltiness perception, though there are contradictory reports to date. The present work aimed to conduct a targeted experiment to ascertain the influence of HPP (300/600 MPa) and cooking (71°C) on saltiness perception and sensory acceptability of meat products. HPP treatment (300/600 MPa) did enhance those two sensory attributes (approx. +1 on a 9-point hedonic scale) in raw (uncooked) cured pork loins but did not in their cooked counterparts. Further, the partition coefficient of sodium (PNa+), as an estimate of Na+ binding strength to the meat matrix, and the content of umami-taste nucleotides were investigated as potential causes. No effect of cooking (71°C) and HPP (300/600 MPa) could be observed on the PNa+ at equilibrium. However, HPP treatment at 300 MPa increased the inosine-5'-monophosphate (IMP) content in raw cured pork loins. Finally, hypothetical HPP effects on taste-mediating molecular mechanisms are outlined and discussed in light of boosting the sensory perception of raw meat products as a strategy to achieve effective salt reductions while keeping consumer acceptability.

Recovery of phenolic compounds from peach pomace using conventional solvent extraction and different emerging techniques.

The study compared high-pressure, microwave, ultrasonic, and traditional extraction techniques. The following extraction conditions were implemented: microwave-assisted extraction (MAE) at 900W power for durations of 30, 60, and 90s; ultrasonic-assisted extraction (UAE) at 100% amplitude for periods of 5, 10, and 15min; and high-pressure processing (HPP) at pressures of 400 and 500MPa for durations of 1, 5, and 10min. The highest yield in terms of total phenolic content (PC) was obtained in UAE with a value of 45.13±1.09mg gallic acid equivalent (GAE)/100g fresh weight (FW). The highest PC content was determined using HPP-500MPa for 10min, resulting in 40mg GAE/100g, and MAE for 90s, yielding 34.40mg GAE/100g FW. The highest value of antioxidant activity (AA) was obtained by UAE in 51.9%±0.71%. The PCs were identified through the utilization of Fourier transform infrared (FTIR) spectroscopy and high-performance liquid chromatography (HPLC). Utilizing multivariate analysis, the construction of chemometric models were executed to predict AA or total PC of the extracts, leveraging the information from IR spectra. The FTIR spectrum revealed bands associated with apigenin, and the application of HPP resulted in concentrations of 5.41±0.25mg/100g FW for apigenin and 1.30±0.15mg/100g FW for protocatechuic acid. Furthermore, HPLC analysis detected the presence of protocatechuic acid, caffeic acid, p-coumaric acid, and apigenin in both green extraction methods and the classical method. Apigenin emerged as the predominant phenolic compound in peach extracts. The highest concentrations of apigenin, p-coumaric acid, and protocatechuic acid were observed under HPP treatment, measuring 5.41±0.25, 0.21±0.04, and 1.30±0.15mg/kg FW, respectively.

Structural, physicochemical and functional properties of high-pressure modified white finger millet starch

The effect of high-pressure processing (HPP) modification (200, 400, and 600 MPa for 10 min) on the physico-chemical, functional, structural, and rheological properties of white finger millet starch (WFMS) was studied. Measured amylose content, water, and oil absorption capacity, alkaline water retention, and pasting temperature increased significantly with the intensity of pressure. All color parameters (L, a, b values, and ΔC) were affected by HPP treatment, and paste clarity of modified starch decreased significantly with an increase in storage time. The samples' least gelation concentration (LGC) is in the range of 8–14 %. An increasing solubility and swelling power are noted, further intensifying at the elevated temperature (90 °C). The structural changes of WFMS were characterized by XRD, SEM, and FTIR spectroscopy. Starch modified at 600 MPa showed a similar pattern as ‘B’-type crystalline, and the surfaces of starch deformed because of the gelatinization. Applied pressure of 600 MPa affected the FTIR characteristic bands at 3330, 2358, and 997 cm−1, indicating a lower crystallinity of the HPP-600 modified sample. According to DSC analysis, even at 600 MPa, WFMS is only partially gelatinized. This work provides insights for producing modified WFM starches by a novel physical modification method.

Effects of high-pressure processing on the physicochemical and adsorption properties, structural characteristics, and dietary fiber content of kelp (Laminaria japonica)

To investigate the effects of high-pressure processing (HPP) on the physicochemical and adsorption properties and structural characteristics of kelp, kelp slice (KS) and kelp powder (KP) were treated under different pressures (300, 450, and 600 MPa) for 5 and 10 min. Compared to untreated KP, HPP-treated KP yielded a 1.31-fold increase in water holding capacity (600 MPa/5 min), a 0.12-fold increase in swelling capacity (450 MPa/10 min), a 1.33-fold increase in oil holding capacity (600 MPa/10 min), a 10-fold increase in glucose adsorption capacity (450 MPa/10 min), and a 0.22-fold increase in cholesterol adsorption capacity (163.1 mg/g DW at 450 MPa/10 min), and exhibited good Cd (Ⅱ) adsorption capacity when its concentration was 10 mmol/L in the small intestine. The physicochemical properties of HPP-treated KS were not improved due to its low specific surface area. In addition, HPP treatment efficiently reduced the particle size of KP and increased its total and soluble dietary fiber content by 17% and 63% at 600 MPa/10 min, respectively. Scanning electron microscope micrographs demonstrated that the surface of HPP-treated KP was rough and porous, and the specific surface area increased with increasing pressure and processing time. To conclude, the results obtained in the present study suggest that HPP is a promising processing method for improving the functionality and structural characteristics of KP and provide a theoretical basis for the utilization of HPP-treated KP as a fiber-rich ingredient in the functional food industry.

Impact of High-Pressure Processing (HPP) on Listeria monocytogenes-An Overview of Challenges and Responses.

High-pressure processing (HPP) is currently one of the leading methods of non-thermal food preservation as an alternative to traditional methods based on thermal processing. The application of HPP involves the simultaneous action of a combination of several factors-pressure values (100-600 MPa), time of operation (a few-several minutes), and temperature of operation (room temperature or lower)-using a liquid medium responsible for pressure transfer. The combination of these three factors results in the inactivation of microorganisms, thus extending food shelf life and improving the food's microbiological safety. HPP can provide high value for the sensory and quality characteristics of products and reduce the population of pathogenic microorganisms such as L. monocytogenes to the required safety level. Nevertheless, the technology is not without impact on the cellular response of pathogens. L. monocytogenes cells surviving the HPP treatment may have multiple damages, which may impact the activation of mechanisms involved in the repair of cellular damage, increased virulence, or antibiotic resistance, as well as an increased expression of genes encoding pathogenicity and antibiotic resistance. This review has demonstrated that HPP is a technology that can reduce L. monocytogenes cells to below detection levels, thus indicating the potential to provide the desired level of safety. However, problems have been noted related to the possibilities of cell recovery during storage and changes in virulence and antibiotic resistance due to the activation of gene expression mechanisms, and the lack of a sufficient number of studies explaining these changes has been reported.

Foodborne pathogen inactivation in fruit juices utilizing commercial scale high-pressure processing: Effects of acidulants and pH.

The effects of juice pH, type of acidulant, and post-treatment refrigeration on the high-pressure processing (HPP) inactivation of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in acid beverages were evaluated. Inoculated apple, orange, and grape juices (at their original pH and adjusted to pH 4.00, 4.50, and 5.00) were treated at 550 MPa for 1 min at 5 °C. In addition, inoculated model solutions acidified to a pH of 5.00 with acetic, citric, malic, and tartaric acids were treated at 400 MPa for 1 min at 5 °C. The effect of refrigerated storage for 24 h after treatment on pathogen inactivation in both experiments was also assessed. A greater than 5-log reduction of the three pathogens inoculated was achieved in all juices immediately after HPP at the juices' original pH, and of L. monocytogenes under all experimental conditions. Refrigerated storage for 24 h after HPP treatment improved the inactivation of E. coli O157:H7, to >5-log reduction, at pH 4.00 in apple juice and of Salmonella in the three juices at pH 4.00. The type of acidulant did not significantly (p > 0.01) affect E. coli or Salmonella inactivation in acidified model solutions but a greater than 5-log reduction after HPP was only achieved for L. monocytogenes when acetic acid was used. The effectiveness of HPP for pathogen inactivation depended largely on product pH and the target pathogen of concern.

Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part I. The effects on pectin extraction and structural properties

The possibility of utilizing endogenous plant pectin methyl-esterase (PME) to modify pectin in source material prior to pectin extraction is proposed and explored in this study. This is based on the reports about activation of endogenous PME in plant-based foods by high-pressure processing (HPP) treatment. Fresh orange (Hamlin) peel from a local commercial juice plant was pretreated with HPP at different combinations of pressures and durations, followed by pectin extraction with a commercial method. The effects of HPP pretreatments on pectin yield and structural properties of the extracted pectins were determined. HPP pretreatment increased the yield of subsequent pectin extraction by 41.10 %. Crude extracts from HPP-treated peels showed higher PME activities than the untreated peel. Pectins extracted from HPP pretreated peel (Hp) had a lower degree of methyl-esterification (DM), accompanied by an increase in degree of blockiness (DB) of non-esterified galacturonic acid (GalA) than the control (pectin extracted from un-treated peel). GalA content and linearity of pectin (LP) were higher, while neutral sugar content and degree of branching (DBr) were lower in Hp. The reduction in weight average molecular weight of Hp was minor, and it was positively correlated with a reduction in neutral sugars, indicating an effect of pectin debranching without degradation of the pectin main chain. The effects of HPP on the pectin main chain, degree, and distribution of methyl-esterification in this study were similar to the reported effects of orange PME on extracted pectin. The identified pectin structural features were validated by Fourier Transform Infrared Spectroscopy analysis and a newly developed lateral flow assay. The study indicates that HPP modification of pectin structure in fresh orange peel before pectin extraction may be an efficient and economical way to generate pectin with desirable structural features and to increase pectin yield.

Phytochemicals, antioxidant capacities and volatile compounds changes in fermented spicy Chinese cabbage sauces treated by thermal and non-thermal technologies

To extend shelf life of fermented spicy Chinese cabbage sauce at room temperature, the effects of electron beam irradiation (EBI), high pressure processing (HPP), pasteurization (PT) and autoclave sterilization (AS) treatments on the colony counts of Lactobacillus plantarum, phytochemicals, antioxidant activities and volatile compounds were investigated. Results showed that thermal and non-thermal treatments could significantly decrease the colony counts of Lactobacillus plantarum, in which EBI and AS treatments inactivated Lactobacillus plantarum thoroughly. EBI and HPP treatments were superior to PT and AS treatments in terms of volatile compounds, bioactive compounds and antioxidant activities. The total contents of volatile compounds in sauces treated by EBI and HPP were significantly increased by 43.92%–61.87% and 71.53%–84.46%, respectively, and the new formed substance 2,3-butanedione endowed sauces with sweet and creamy aroma. In addition, HPP treatment improved the extractable contents of total phenolics and carotenoids, retained capsicum red pigment content, and significantly enhanced antioxidant capacities of sauces. Sauce treated by HPP at 200 MPa exhibited the highest total carotenoid content, DPPH radical scavenging activity and FRAP, increasing by 9.27%, 2.24% and 16.13%, respectively, compared with CK. EBI treatment exhibited higher total phenolic content and FRAP, which positively depended on the dose. Therefore, HPP and EBI treatments were suggested as potential technologies to improve shelf-life stability and volatile compounds of fermented spicy Chinese cabbage sauce.

Pilot Scale Assessment of High-Pressure Processing (HPP) to Enhance Microbiological Quality and Shelf Life of Fresh Ready-to-Eat (RTE) Blue Crab Meat.

Blue crab (Callinectes sapidus) is a highly valuable wild fishery species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico. The annual commercial production of live blue crabs is approximately 50,000 metric tons with a dockside value of USD 200 million. Presently the US blue crab processing industry sells crab meat in three basic forms: fresh crab meat, pasteurized crab meat, and frozen crab meat. By far "Fresh" is the most desirable form of crab meat. However, fresh crab meat has a limited shelf life. This study evaluated the effects of high-pressure processing (HPP) on enhancing the microbiological quality and shelf life of blue crab meat. Live blue crabs were pressure-cooked in a retort (≥115 °C for 4-6 min). The crab meat was handpicked, packed in plastic containers with seals, subjected to HPP treatment, and stored at 4 °C. Container integrity and water leakage issues were examined by observation in addition to weight comparison before and after HPP treatment; the shelf life of crab meat with and without HPP treatments was examined via microbiological tests and sensory evaluations. Results show that polypropylene containers sealed with 10K OTR (oxygen transmission rate) film could withstand high pressure without water leakage issues; HPP treatment at 600 MPa for 3 min could extend the shelf life of fresh, cooked, and handpicked crab meat from 6 days to 18 days based on the strictest APC (aerobic plate account) limit (APC ≤ 100,000 CFU/g). The sensory quality of the HPP-treated crab meat was well accepted throughout the 3-week storage period. The results support the use of HPP as an effective non-thermal processing technology to enhance the microbiological quality and extend the shelf life of fresh RTE blue crab meat.

Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part II. The effects on gelling capacity and emulsifying properties of pectin

The most important functionalities of pectin are gelling and emulsifying properties, which can be tailored by modifying pectin structure through chemical/enzymatic treatments or physical processes. In a companion article (Zhao et al., 2023), the modification of pectin structure with high-pressure processing (HPP) was reported. In this study, the functionalities of the HPP-modified pectins (Hp) were evaluated and compared with commercial low methoxy (LM) and high methoxy (HM) pectins. The calcium sensitivity of Hp was comparable to that of commercial LM pectin, which was remarkably higher than the control pectin extracted from untreated peel and commercial HM pectin. Hp had a dramatically higher gelling capacity for calcium-mediated gelation than the control and commercial HM pectin. The strength and viscoelastic properties of Hp-calcium gels were comparable to that of commercial LM pectin. Meanwhile, most of the Hp also showed a comparable gelling capacity for sugar-acid-mediated gelation to that of the control and commercial HM pectin. Hp also had higher emulsifying stability than the control and commercial pectins. The increased capacity of Hp for calcium-mediated gelation was attributed to the block-wise distribution of non-esterified galacturonic acid (GalA) introduced by the HPP treatment, and the higher emulsifying stability was mainly attributed to the debranching of pectin. The study further confirmed that pectin functionalities were highly correlated with its structural properties. The data reveal the great potential of producing low-cost, high-quality pectins with increased gelling capacity and a broadened scope of applications, by adding a simple HPP pretreatment of fresh source material for pectin extraction.

Functionality of process cheese made from Cheddar cheese with various rennet levels and high-pressure processing treatments

Due to its versatility and shelf stability, process cheese is gaining interest in many developing countries. The main structural component (base) of most processed cheese formulations is young Cheddar cheese that has high levels of intact casein. Exporting natural Cheddar cheese base from the United States to distant overseas markets would require the aging process to be slowed or reduced. As Cheddar cheese ripens, the original structure is broken down by proteolysis and solubilization of insoluble calcium phosphate. We explored the effect of varying rennet levels (we also used a less proteolytic rennet) and application of high-pressure processing (HPP) to Cheddar cheese, as we hoped these treatments might limit proteolysis and concomitant loss of intact casein. To try to retain high levels of insoluble Ca, all experimental cheeses were made with a high-draining pH and from concentrated milk. To compare our intact casein results with current practices, we manufactured a Cheddar cheese that was prepared according to typical industry methods (i.e., use of unconcentrated milk, calf chymosin [higher levels], and low draining pH value [∼6.2]). All experimental cheeses were made from ultrafiltered milk with protein and casein contents of ∼5.15% and 4.30%, respectively. Three (low) rennet levels were used: control (38 international milk clotting units/mL of rennet per 250 kg of milk), and 25% and 50% reduced from this level. All experimental cheeses had similar moisture contents (∼37%) and total Ca levels. Four days after cheese was made, half of the experimental samples from each vat underwent HPP at 600 MPa for 3 min. Cheddar cheese functionality was monitored during aging for 240 d at 4°C. Cheddar cheese base was used to prepare process cheese after aging for 14, 60, 120, 180, and 240 d. Loss tangent (LT) values of cheese during heating were measured by small strain oscillatory rheology. Intact casein levels were measured using the Kjeldahl method. Acid or base titrations were used to determine the buffering capacity and insoluble Ca levels as a percentage of total Ca. The LTmax values (an index of meltability) in process cheese increased with aging for all the cheese bases; the HPP treatment significantly decreased LTmax values of both base (natural) and process cheeses. All experimental cheeses had much higher levels of intact casein compared with typical industry-make samples. Process cheese made from the experimental treatments had visually higher stretching properties than process cheese made from Cheddar with the typical industry-make procedure. Residual rennet activity was not affected by rennet level, but the rate of proteolysis was slightly slower with lower rennet levels. The HPP treatment of Cheddar cheese reduced residual rennet activity and decreased the reduction of intact casein levels. The HPP treatment of Cheddar cheese resulted in process cheeses that had slightly higher hardness values, lower LTmax values, and retained higher storage modulus values at 70°C. We also observed that the other make procedures we used in all experimental treatments (i.e., using a less proteolytic chymosin, using a concentrated cheese milk, and maintaining a high draining pH value) had a major effect on retaining high levels of intact casein.

Effects of high-pressure processing on the physicochemical properties of prosciutto and microbe inactivation

In this study, the effect of high-pressure processing (HPP) conditions (0.1–600 MPa) on the physicochemical properties, inactivation of microorganisms such as hepatitis E virus pathogen, Escherichia coli, and Listeria monocytogenes and total cell number in prosciutto were evaluated. In the results of appearance and pH, there was no tendency according to level of HPP. The results of hardness were decreased with HPP, and the water content, and water-holding capacity were increased compared to control (0.1 MPa) due to leading to changes in the protein structure of prosciutto. Above 500 MPa, lipid oxidation was significantly decrease and protein oxidation was slightly increase. In the results of microbial analyses above 500 MPa, E. coli and L. monocytogenes were reduced by approximately 4- and 1-log (p < 0.05), respectively and the viral content slightly decreased in HPP samples compared to those in the control. These results indicate that HP treatment above 500 MPa for 9 min is an effective strategy for enhancing food safety, advancing the non-thermal food industry. With further study, it will be necessary to confirm whether HPP treatment has a positive effect on sensory evaluation.

High pressure processing of whole soymilk: Effect on allergenicity, anti-nutritional factor, lipoxygenase activity and E-nose-aroma characteristics

Soymilk was subjected to high pressure processing (HPP) at different pressure levels (300–600 MPa) and time (5, 15 and 25 min) intervals. After the HPP treatment, a mild reduction was observed in soymilk pH and conductivity values; however, a sudden surge in the protein content (17.34±0.10 mg/ml) was recorded at 600 MPa (5 min) treatment. When soymilk proteins were evaluated for their structural changes, FTIR (amide regions), CD spectra, and UV inflorescence showed the positive responses and as the result, soy Kunitz trypsin inhibitor (SKTI) antigen binding ability reduced from 100% to 44.39±8.50% at 300 MPa (5 min). However, prolong exposure at 300 MPa had a negative effect on allergenicity. Nevertheless, HPP treatment reduced the lipoxygenase (100.00% to 68.13±12.80%) and trypsin inhibitor (100.00% to 91.30±1.45%) activities. In addition, the treatment also slightly altered the viscosity, whiteness, and volatile aroma components of soymilk after HPP treatment. Principal component analysis revealed that among 22 selected volatiles, only those belong to PC1 and PC2 caused 68% variance in aroma changes. Overall, HPP treatment reduced allergenicity, trypsin inhibitor activity and lipoxygenase activity without modifying the soymilk nature. Further, it also reduced the beany flavor inducing hexanal volatile content after the treatment.

Comparison of high-hydrostatic pressure and frozen treatments on raw freshwater clam marinated in soy sauce: Impact on microbiological and organoleptic qualities

The purpose of this study was to compare how the two different methods of food processing, high pressure processing (HPP) under 300–500 MPa for 3 min and freezing, affect the microbiological, chemical, and organoleptic qualities of soy sauce-marinated freshwater clams (Corbicula fluminea) during refrigeration. The aerobic plate count (APC), psychotropic bacteria count (PBC), Salmonella spp., and coliform of high pressure processed soy sauce-marinated clams (HPP marinated-clams) were obviously lower than conventionally frozen soy sauce-marinated clams (frozen marinated-clams), or were not detected. In addition, after all samples’ 15-day refrigeration period, HPP was found to significantly inhibit the growth of APC, PBC, Salmonella spp., and coliform, while the microbial counts of frozen marinated-clams increased gradually with time. However, the surface areas, moisture contents, and salt contents of all samples of both HPP marinated-clams and frozen marinated-clams slightly increased during refrigeration. Furthermore, the results of organoleptic analyses exhibited that the storage life of marinated clams can be increased from 9 days under freezing treatment to 15 days under HPP (300 MPa and 500 MPa). Using high-throughput sequencing, HPP treatment significantly changed the microbiota of marinated clam and delayed the spoilage process. Therefore, the study suggests using HPP at least 300 MPa for 3 min to effectively inhibit the microbial growth and significantly extend the storage life of the samples during the refrigeration period. This is a first study to use HPP technology to replace the traditional freezing technology in the application of raw soy sauce-marinated freshwater clam products, and at the same time, HTS was used to evaluate the changes of microbiota during refrigeration.