High Pressure Processing Processing Research Articles

Survival modelling of infectious human norovirus and surrogates for high-pressure inactivation in strawberry puree

Berries contaminated with human norovirus (HuNoV) have been frequently identified as a cause of foodborne gastroenteritis. To prevent virus transmission while preserving sensory and quality parameters, non-thermal treatments, such as high-pressure processing (HPP), can be applied to the berries and products thereof. Here, strawberry purees contaminated with HuNoV genogroup I (GI.3[P13]) and II (GII.4 Sydney [P16]), along with murine norovirus (MNV) and Tulane virus (TV) serving as surrogates, were exposed to HPP at several pressure-time combinations. Virus inactivation was assessed by cell culture, including the novel human intestinal enteroids (HIE) model for HuNoVs. The infectivity results showed TV more resistant than MNV to HPP, as also confirmed by kinetic mathematical modelling. Results indicated that a holding pressure of 450 MPa and an exposure time of ≥5 min are reliable operational conditions for HPP process to successfully control viral contamination. In addition, the inactivation models deduced from MNV and TV viruses were challenged with experimental HuNoV GII.4 infectivity resulting in bias factors <1 for all treatment conditions. This finding validates the proposed models for the conservative estimation of HuNoV inactivation. Our work offers a blueprint for moving forward with inactivation studies using the HIE system, which provides useful practical information on optimum treatments for the best public health outcomes.

The High Pressure Preservation of Honey: A Comparative Study on Quality Changes during Storage.

In commercially available honey, the application of a heat treatment to prevent spoilage can potentially compromise its beneficial properties and quality, and these effects worsen with extended storage. The high-pressure processing (HPP) of honey is being explored, but its long-term impact on honey quality has not been characterised yet. This study evaluated the effects of HPP and thermal processing on the microbial load, physicochemical quality (i.e., hydroxymethylfurfural content and diastase activity), and antioxidant capacity of honey after treatment and following extended storage (6, 12, and 24 months) at 20 °C. Pasteurization (78 °C/6 min) effectively eliminated the microorganisms in honey but compromised its physicochemical quality and antioxidant activity. HPP initially showed sublethal inactivation, but storage accelerated the decrease in yeasts/moulds and aerobic mesophiles in honey (being <1 log CFU/g after 24 months of storage) compared to unprocessed honey and honey thermally treated under mild conditions (55 °C/15 min). The physicochemical characteristics of the quality of HPP-treated honey and raw unprocessed honey did change after long-term storage (24 months) but remained within regulatory standards. In conclusion, HPP emerged as a more suitable and safe preservation method for Apis mellifera honey, with a minimal risk of a loss of antioxidant activity compared to traditional industrial honey pasteurization.

A Quality Assessment of Strawberry Nectar Stabilized by Thermal and High-Pressure Processing Conditions

This study is aimed at evaluating the quality of strawberry nectar following high-pressure processing (HPP) at different pressure levels (400, 500, and 600 MPa for 3 minutes) and thermal pasteurization (TT) at 75°C for 15 s. Key parameters include total colour difference ( Δ E ∗ ), aparent viscosity, colour analysis via CIELAB coordinates, and pH. Additionally, residual enzymatic activity (RA%) of polyphenol oxidase (PPO) and peroxidase (POD) was measured. Strawberry nectar (12°Brix) was prepared and subjected to processing, with thermal treatment in 50 mL tubes and HPP in 40 mL polyethylene bags. Samples were stored under refrigeration during 21 days, with microbial analysis conducted to assess microbiological stability during storage. TT exhibited a more pronounced reduction in total aerobic microbial count (TAMC) compared to HPP, which showed no detectable yeast and mould. Apparent viscosity varied among samples, with HPP at 600 MPa displaying a significant increase of 52.1% compared to the control. The pseudoplastic behavior, characterized by n values lower than 1, was consistent across all treatments. TT led to a reduction in L ∗ brightness value during storage, whereas HPP-treated samples underwent colour changes over time with Δ E ∗ of 3.1 for 400 MPa, 3 minutes, at 21 days. For PPO and POD, the 600 MPa treatment exhibited the highest inhibition (44% and 4% RA, respectively). This comprehensive study provides insights into how different HPP processing conditions affect the quality attributes, enzymatic activity, and microbiological stability of strawberry nectar during production and refrigerated storage. The research’s significance lies in its holistic comparison of HPP with traditional thermal pasteurization, offering valuable information for both industry and consumers.

Separation of α-Lactalbumin-Enriched Fractions from Caprine and Ovine Native Whey Concentrate by Combining Membrane and High-Pressure Processing.

Whey from goat and sheep have been gaining attention in the last few years for their nutritional properties. Unfortunately, β-Lg, not found in human milk, may trigger infant allergies if used in infant food formulations, so there is a growing interest in developing ingredients derived from whey with higher α-La/β-Lg ratios. The objective of this work was to study the effect of high-pressure processing (HPP) on caprine and ovine native whey concentrates (NWC) in order to obtain α-Lactalbumin (α-La)-enriched fractions. NWCs were treated at 600 MPa (23 °C) for 2, 4, and 15 min and two pH conditions were studied (physiological pH and pH 4.60). The concentration of β-Lg in supernatant fraction after HPP significantly decreased after 2 min of treatment, while the concentration of α-La was unchanged in both goat and sheep samples. Longer HPP processing times (up to 15 min) progressively increased α-La purification degree but also decreased the α-La yield. Caprine and ovine NWCs treated at physiological pH provided better α-La yield, α-La purification degree, and higher β-Lg precipitation degrees than the corresponding acidified samples, while the corresponding NWC supernatant (NWCsup) showed lower values for both surface hydrophobicity and total free thiol indices, suggesting a higher extent of protein aggregation. Effects of sample acidification and the HPP treatment were opposite to those previously reported on bovine NWC, so further characterization of caprine and ovine β-Lg should be carried out to understand their different behavior.

Application of HPP for the Development of a Dessert Elaborated with Casein and Cocoa for a Dysphagia Diet.

In this study, the application of high-pressure processing (HPP) for optimizing the texture of a cocoa dessert rich in casein and developed for people with dysphagia was investigated. Different treatments (250 MPa/15 min; 600 MPa/5 min) and protein concentrations (10-15%) were combined and evaluated for choosing the optimum combination leading to an adequate texture. The selected formulation was a dessert containing 4% cocoa and 10% casein and subjected to 600 MPa for 5 min. It showed a high nutritional value (11.5% protein) and high antioxidant capacity, which was slightly affected by the HPP processing. The rheological and textural properties showed that HPP had a clear effect on the dessert structure. The loss tangent decreased from 2.692 to 0.165, indicating the transition from a liquid to a gel-like structure, which is in a suitable range for dysphagia foods. During storage (14 and 28 days at 4 °C), progressive significant changes in the structure of the dessert were observed. A decrease in all rheological and textural parameters occurred, except for the loss of tangent, which increased its value. In any case, at 28 days of storage, samples maintained the weak gel-like structure (0.686 loss tangent) that is acceptable for dysphagia management.

High pressure inactivation of Escherichia coli and Staphylococcus aureus in pineapple puree (variety MD2) and preliminary quality evaluation during chilled storage

The increased demand in the global pineapple market from Malaysia makes the focus on downstream processing even more important. However, contamination of fruit purees with foodborne pathogens could take place during processing and post-processing handling. In this study, the efficiency of high-pressure processing (HPP) was investigated against aseptically inoculated Escherichia coli ATCC® 25922™ and Staphylococcus aureus ATCC® 25923™ in pineapple puree. Pineapple (Ananas comosus) variety MD2 was chosen for HPP treatment due to Malaysia’s competitive advantage in the global pineapple market. An 8-log reduction of E. coli and S. aureus (p&lt;0.05) in pineapple puree during HPP (400 MPa for 5 mins at 30oC processing temperature) in this research making HPP an effective technology. In this study, S. aureus showed a higher inactivation effect than E. coli in HPP-treated pineapple puree. Untreated pineapple puree samples with inoculated pathogens were kept as control samples. Knowledge of food safety is necessary for a reliable HPP process; hence a preliminary storage study was added to compare the chemical and microbiological quality between HPP-treated pineapple puree and heattreated pineapple puree. Interestingly, HPP-treated samples effectively retained vitamins A, B1, B2 and C close to fresh samples (control) during 0 months, and vitamin A was retained after 6 months of storage. The microbiological results also showed that HPPtreated samples were microbiologically safe during chilled storage for a minimum of 6 months based on international microbiological standards. In summary, E. coli and S. aureus inactivation can be accelerated with pressure higher than 400 MPa at 30oC processing temperature within 5 mins and HPP successfully maintained the safety of pineapple puree for a minimum of 6 months.

Effect of High Hydrostatic Pressure Processing on Starch Properties of Cassava Flour

The aim of this study was to utilize high-pressure processing (HPP) to modify cassava flour through altering the starch components. Specifically, the effect of HPP processing variables, i.e., pressure (0.10 or untreated, 300, 400, 500, and 600 MPa), flour concentration (FC; 10, 20, and 30%), and holding time (HT; 10 and 30 min) on starch-related properties was studied. Microstructural integrity, thermal properties, and starch susceptibility to digestive enzymes were determined. A three-way ANOVA was performed to identify the interaction effect between these process variables. In general, 600 MPa consistently transformed the crystalline starch into an amorphous one. HPP-induced gelatinization led to enlarged starches with loss of birefringence, reduced relative crystallinity percentage, and changes in short-range order. The three-way interaction between the process variables was evident in the significant progressive rise in onset gelatinization temperature and degree of gelatinization, and the decline in gelatinization enthalpy from 500 to 600 MPa with decreasing FC and increasing HT. These changes caused an increased percentage of rapidly digestible starch and decreased resistant starch fraction. Overall, this study’s results imply the possibility of using HPP to modify the starch component in cassava flour and potentially create flours with varying levels of functionalities.

Impact of High-Pressure Processing and Sous Vide Cooking on the Physicochemical, Sensorial, and Textural Properties of Fresh Whiteleg Shrimp (Litopenaeus setiferus)

ABSTRACT Consumers have a growing preference for convenient, fresh, and healthy seafood products with natural flavor, color, taste, and extended shelf life. High-pressure processing (HPP) and sous-vide cooking (SVC) are two methods that are applied in the food industry to extend the shelf life and enhance the natural flavor of shrimps. This study aimed to investigate the effect of the combination of HPP (300 MPa/350 MPa/400 MPa) and SVC (65°C/15 min) on the physicochemical, sensorial, and textural (hardness) properties of fresh white shrimp (Litopenaeus setiferus). A decrease in hardness of samples treated with HPP was observed. Sensory and textural evaluation by consumers (n = 28) showed that the shrimp samples treated at 300 and 350 MPa were preferred. The results suggest that the combination of HPP and SVC processing affects the sensory and texture of fresh whiteleg shrimp (p ≤ .05). These findings indicate that combining HPP and SVC has the potential to produce minimally processed value-added shrimp products that are acceptable to consumers.

Preparation of curcumin-loaded liposome with high bioavailability by a novel method of high pressure processing

Curcumin has been incorporated for the development of new products with applicability in food, pharmaceutical and cosmetic fields in Asia, due to the traits of anti-oxidation and anti-inflammatory. In the application of food engineering, high-pressure processing (HPP) can destroy non-covalent bonds and use as a method to inactivate bacteria for extending the perseveration of food. Thus, this study focuses on a novel approach for the microencapsulation of curcumin by the combination of ethanol injection and HPP at the room temperature for stabilizing pure curcumin in aqueous solutions and in liposome. The results revealed that the most optimal curcumin-liposome was prepared by HPP at operational pressure of 200 MPa within 5 mins holding time to obtain the minimum particle size of 281.9 nm, encapsulation efficiency of 87.25% and polydispersity index (PDI) of 0.23. Particle size could reduce to nanoscale (70.65 nm) after 0.5% addition of Tween 80, but the encapsulation efficiency spontaneously decreased to 45.05%. It is an option to produce liposome with nanosize and uniform distribution for the consideration of high drug delivery. Conclusively, HPP process could not only effectively decrease particle size and PDI of liposome but also efficiently sterilize bacteria around concentration of 103 CFU/g.

A comparative study on physicochemical properties and in vitro bioaccessibility of bioactive compounds in rosehip (Rosa caninaL.) infusions treated by non‐thermal and thermal treatments

The present study aimed to compare the effects of non-thermal techniques with thermal treatment on physicochemical properties, bioaccessibility, and antioxidant capacity of bioactives in rosehip (Rosa canina) infusions. High pressure processing (HPP) at 200, 400, or 600 MPa for 5 and 15 min; pulsed electric field (PEF) with 5, 10, and 15 kJ/kg specific energy intakes at 1 and 3 kV/cm electric field strength; and thermal treatment (TT) at 85°C/10 min were applied. According to the results, processing method had varying effects on the contents of phenolic compounds, antioxidant capacity, and bioaccessibility in rosehip infusions. The highest retention of total phenolics (TPC) and flavonoids (TFC) were achieved by the TT (2278 mg gallic acid equivalents (GAE)/100 g dry weight (dw) and 3728 rutin equivalents (RE)/100 g dw, respectively) and HPP treatment at a pressure of 600 MPa for 15 min (2268 mg GAE/100 g dw and 3695 mg RE/100 g dw, respectively). These findings are in line with the results of antioxidant capacities of the samples. Besides, TT, HPP treatment at 600 MPa/5 min, and PEF treatment at 5 and 15 kJ/kg energy intakes (PEF1 and PEF3) resulted with a higher recovery of TPC, TFC, and antioxidant capacity after gastrointestinal digestion. It can be concluded that HPP and PEF treatments at specific conditions could be used in the processing of infusions and beverages. However, it should be considered that appropriate processing parameters should be selected and optimized for each sample individually, to assure the best nutritional value and quality characteristics. Novelty impact statement Better retention of bioactive compounds after high pressure processing (HPP) treatment at a pressure of 600 MPa for 15 min. A noticeable improvement in the recovery of bioactive content and antioxidant capacity after HPP and pulsed electric field processing. Potential of non-thermal food processing techniques as alternative to conventional thermal treatments in the production of functional foods with enhanced nutritional value.

Effect of high-pressure processing to improve the safety and quality of an Quercus acorn beverage

The development of an acorn beverage can be an opportunity to increase the intake of bioactive compounds and add value to Quercus acorn. However, unprocessed plant-based beverages have a very short shelf-life and thermal treatments affect their overall quality. High-pressure processing (HPP) emerges as a possible solution to better retain nutritional properties and sensorial quality and extend shelf-life. This research assessed the impact of HPP (450/600 MPa, 5/12.5/20 min) and thermal processing (TP, 85 °C, 30 min) on an acorn beverage during 63 days of refrigerated storage (4 °C). From all processing conditions, HPP at 450 MPa for 5 min showed to be suitable to assure microbiological safety (mesophiles, psychrophiles, yeasts and moulds, and Enterobacteriaceae) during 63 days and to better preserve total soluble solids and colour. The antioxidant activity (ABTS/DPPH) was similar to higher for heat-treated samples, being gallic acid the main phenolic compound found in the beverage. Total carbohydrates, lipids, proteins, minerals, and fatty acids contents were similar for HPP and TP. This beverage revealed low thrombogenicity and atherogenicity indices, and potassium as the main mineral. Concluding, HPP extended the shelf-life of the beverage and improved the physicochemical quality, revealed by panellists preference, as revealed by sensorial analysis.

Recovery of high pressure processing (HPP) induced injured Escherichia coli O157:H7 inhibited by Lactobacillus sakei on vacuum-packed ground beef

High pressure processing (HPP) has been demonstrated as an effective technique in reducing E. coli O157:H7 levels on beef. However, an “injure and recover” action of E. coli O157:H7 was found to raise their beef contamination after HPP disinfection. Furthermore, the recovered cell could be miscalculated owing to the complex bacterial community of meat. Therefore, the current work was aimed to evaluate the recovery of HPP treated pressure resistant E. coli O157:H7 with the existence of background bacteria on beef. In brief, inactivation, injury and pressure resistance of four E. coli O157:H7 strains, CICC 21530, NCTC 12900, and two strains isolated from beef (B1, and B2), were firstly evaluated using selective media. The lethal and injured ratio of E. coli CICC21530 was 62.21% and 64.29% after pressure processing at 400 MPa, while the other three strains were all under the detection limit. Thus, the most pressure-resistant strain CICC21530 was selected and inoculated into ground beef with and without Lactobacillus sakei, one of the predominant spoilage bacteria in vacuum-packed meat, respectively, to study their injured cell recovery after HPP treatment. The results indicated good pressure resistance and recovery ability of L. sakei 1018, that after treatment at 400 MPa for 10 min, the lethal rate was only 31.23%, and the enumeration of HPP treated L. sakei 1018 cells reached their initial level in 3 days. Besides, for the mixed L. sakei 1018 and E. coli CICC21530 inoculation, the spoilage bacterium L. sakei 1018 in vacuum packaging beef inhibited the recovery of E. coli tremendously during all the storage period after HPP process.

Effects of different stabilization techniques on the shelf life of cold brew coffee: Chemical composition, flavor profile and microbiological analysis

Cold brew coffee is a beverage prepared at low temperatures and over long brewing times resulting in particular physicochemical and sensory characteristics. This type of coffee is usually consumed immediately after preparation or after short storage in refrigerated conditions. However, in recent years many commercial coffee vendors started investing in ready-to-drink cold brew coffees packaged for extended storage. These products present the potential problem of microbial and sensorial alteration. In this study we evaluated five different stabilization techniques with the aim to extend the shelf life of the cold brew coffee while preserving its peculiar organoleptic properties, e.g. HPP (High Pressure Processing), microfiltration, UV irradiation, pasteurization and blast chilling process. The effects were investigated over four months, evaluating the caffeine and the chlorogenic acids contents by HPLC-DAD analysis and carrying out anevaluation of selected volatile compounds by HS-SPME-GC-MS. After four months of storage, the samples treated with pasteurization and HPP maintained a stable content of caffeine and chlorogenic acids, guaranteeing also the microbiological safety of the beverage. At the same shelf-time, the pasteurized samples showed an unaltered flavor profile, while a decrease of about 25% of the total content of volatile compounds was registered for the HPP sample.

Inactivation of Foodborne Viruses by High-Pressure Processing (HPP).

High-pressure processing (HPP) is an innovative non-thermal food preservation method. HPP can inactivate microorganisms, including viruses, with minimal influence on the physicochemical and sensory properties of foods. The most significant foodborne viruses are human norovirus (HuNoV), hepatitis A virus (HAV), human rotavirus (HRV), hepatitis E virus (HEV), human astrovirus (HAstV), human adenovirus (HuAdV), Aichi virus (AiV), sapovirus (SaV), and enterovirus (EV), which have also been implicated in foodborne outbreaks in various countries. The HPP inactivation of foodborne viruses in foods depends on high-pressure processing parameters (pressure, temperature, and duration time) or non-processing parameters such as virus type, food matrix, water activity (aw), and the pH of foods. HPP was found to be effective for the inactivation of foodborne viruses such as HuNoV, HAV, HAstV, and HuAdV in foods. HPP treatments have been found to be effective at eliminating foodborne viruses in high-risk foods such as shellfish and vegetables. The present work reviews the published data on the effect of HPP processing on foodborne viruses in laboratory media and foods.

Evaluation of high pressure processing (HPP) inactivation of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in acid and acidified juices and beverages

Increasing consumer demand for high-quality foods has driven adoption by the food industry of non-thermal technologies such as high pressure processing (HPP). The technology is employed as a post-packaging treatment step for inactivation of vegetative microorganisms. In order to evaluate HPP inactivation of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in acid and acidified juices and beverages, pressure tolerance parameters were determined using log-linear and Weibull models in pH-adjusted apple juice (pH 4.5) at 5 °C. A commercial processing HPP unit was used. The Weibull model better described the inactivation kinetics of the three tested pathogens. According to estimates from the Weibull model, 1.5, 0.9, and 1.5 min are required at 600 MPa to produce 5-log reductions of E. coli, Salmonella, and L. monocytogenes, respectively, whereas according to the log-linear model, 3.2, 1.8, and 2.1 min are required. The effects of process conditions were verified using commercial products (pH between 3.02 and 4.21). In all tested commercial juices or beverages, greater than 5-log reductions were achieved for all tested pathogens using HPP process conditions of 550 MPa for 1 min. These findings demonstrate that the HPP conditions of 600 MPa for 3 min, typically used by the food industry provide an adequate safety margin for control of relevant vegetative pathogens in acid and acidified juices and beverages (pH < 4.5). Results from this study can be used by food processors to support validation studies and may be useful for the future establishment of safe harbors for the HPP industry.

Starch-Based Hydrogels Produced by High-Pressure Processing (HPP): Effect of the Starch Source and Processing Time

Starch-based hydrogels are natural polymeric structures of high scientific interest in the food, pharma, and cosmetic sectors. In this work, the effects of the starch source (rice, corn, wheat, and tapioca starch) and processing time (600 MPa for 5 and 15 min) on gel formation and on the physical characteristics of the structures formed were evaluated. At the pressure level utilized, all the starches were completely gelatinized regardless of the processing time tested. The hydrogels obtained displayed a shear-thinning and gel-like behavior (G' > G). HPP, under the processing conditions tested, was more effective in producing hydrogels based on tapioca and rice than on corn and wheat starch. Rice, wheat, and corn starch HPP hydrogels showed a cream-like structure, whereas those based on tapioca starch evidenced a more compact structure. With a HPP processing time of 15 min, tapioca and rice starch HPP hydrogels displayed higher viscosity, G', and firmness, suggesting an overall structural reinforcement. However, with 15 min of processing time, the lightness and whiteness of rice, wheat, and corn starch HPP hydrogels were negatively influenced, presumably as a consequence of the increased amount of water absorbed in starch granules. These results suggest that both the starch source and processing time play an important role in the formation of gels from starch suspensions and affect the physical characteristics of HPP hydrogels. Finally, the natural products obtained might be suitable for use in several applications where either creamy or gummy structures are desirable.

Effect of high-pressure processing on bacterial inactivation in açaí juices with varying pH and soluble solids content

This study evaluated microbial inactivation effects of high-pressure processing (HPP) applied to açaí juices formulated with varying pH and soluble solids content (SSC). Açaí juice with pH 4.3 and 2.9°Brix was initially inoculated with cocktails of 5 strains of E. coli O157:H7, Listeria monocytogenes or Salmonella spp. and processed at varying pressures (300, 400 and 600 MPa) and dwelling times (1 and 3 min) at 5 °C. The lethality at 400 MPa for 3 min was >6-log CFU/mL. Further inactivation was observed during storage under refrigeration in the populations of Salmonella spp. and L. monocytogenes. In order to study the influence of pH and SSC on inactivation of Salmonella spp. by HPP, pH of açaí juice samples was adjusted to a range between 4.0 and 5.5 and SSC was adjusted between 2.9 and 14.9°Brix. The ability of HPP to provide a 5-log reduction in the population of Salmonella spp. was reduced with increasing pH and SSC. Immediately after HPP the juices with pH 4.0 and 2.9°Brix presented >6-log reduction while the one with 8.9°Brix resulted in 5-log reduction. In one week of refrigerated storage (7 °C), the juices (pH 4.0–14.9°Brix and pH 4.5–2.9°Brix) also presented >6-log reduction in Salmonella spp. concentration. These results indicated that a less intense process (below commonly recommended commercial conditions - 600 MPa/3 min) could be applied for açaí juice thus assuring required safety, in addition to an extra microbial inactivation verified during refrigerated storage. Industrial relevanceOur results showed that viability of cells of pathogenic strains continues to fall after processing and that this effect can be reversed in higher pH and higher concentration of soluble solids. This observation can help the design of more efficient protocols for validation of HPP processing, leading to milder processing conditions that will allow reduction of maintenance and energy costs associated with HPP. In addition, our results help to clarify the criteria to be adopted in the microbiological validation of juices processed by high hydrostatic pressure.

The Impact of High-Pressure Processing on Physicochemical Properties and Sensory Characteristics of Three Different Lamb Meat Cuts.

This study investigated the effects of high pressure processing (HPP) on the physicochemical properties and sensory characteristics of different lamb meat cuts. Lamb meat discolouration occurred when HPP was applied at 400 and 600 MPa. Thiobarbituric acid reactive substances (TBARS) values significantly increased with pressure increase from 200 to 600 MPa for loin cut, and 300 to 600 MPa for shoulder and shank cuts. Saturated fatty acid and polyunsaturated fatty acid content significantly decreased with pressure increase from 200 to 600 MPa for shank and shoulder cuts, and 300 to 600 MPa for loin cut. Free amino acids content significantly increased in shank and loin cuts with pressure increase after 200 MPa, and in shoulder cuts after 400 MPa. In addition, samples treated with HPP at high pressure levels of 400 and 600 MPa were associated with browned, livery and oxidized flavours. The pressure levels applied and type of cuts used are important considerations during HPP processing as they influenced physicochemical and sensory properties of lamb samples.

Effects of processing conditions and glycerol concentration on rheological and texture properties of starch-based hydrogels produced by high pressure processing (HPP)

Starch-based hydrogels are natural polymeric structures which could be potentially utilized in food, pharma and cosmetic sectors to produce creams, gels and ointments, as well as functional foods and products for personalized nutrition. In this paper, the effects of processing conditions (pressure levels and holding time) on gelation of corn and rice starch solutions were evaluated also in presence of glycerol. Considering the utmost importance of humectants as active moisturizers in gels, their addition in starch solutions has been investigated in view of the industrial exploitation of HPP starch-based hydrogels.Experimental results demonstrated that at 600 MPa the gelation of the formulations tested was homogenous and the hydrogels formed were stable. However, glycerol at 10% concentration played an antagonistic role, being longer processing times necessary to form gels. Viscosity and G' values of rice and corn starch HPP hydrogels decreased with increasing glycerol concentration, particularly for corn starch hydrogels. At all HPP processing conditions investigated, rice starch solutions containing the humectant were more prone to gelation and the hydrogels formed had better texture properties than those based on corn starch. 5% glycerol concentration was identified as the critical value to obtain stable HPP hydrogels with good rheological and texture properties.

High pressure‐assisted vacuum‐freeze drying: A novel, efficient way to accelerate moisture migration in shrimp processing

High pressure processing (HPP), as nonthermal processing technology, has the potential to increase the drying rate due to its improvement of heat and mass exchange in different processes. In this study, the moisture migration in shrimps during HPP-vacuum-freeze drying (HPP-VFD) processes has been monitored by using low-field nuclear magnetic resonance and magnetic resonance image (MRI) in comparison with hot air-drying and VFD. Based on the T2 relaxation spectra, three water fractions corresponding to bound water (hydrogen-bonded water), immobile water (water trapped by organization structure or cell member), and free water were observed. For group B, with increasing drying time (4 to 22 hr), the transverse relaxation times of T21 , T22 , and T23 were significantly decreased (76.79%, 57.78%, and 40.9%) (P < 0.05). The content of immobile water (A22 ) and free water (A23 ) decreased (81.55% and 89.07%), whereas the bound water (A21 ) increased (7.26%). In comparison with group B, the T21 , T22 , and T23 of group C showed greater decrease (83.12%, 87.12%, and 89.57% for group C) so that HPP pretreatment could shorten the relaxation time. MRI analysis further proved that HPP-VFD drying has improved drying efficiency, and moisture migration was from the exterior to the interior part with increasing drying time. SEM analysis demonstrated that no significant damage of muscle fibers with narrower gaps was observed for groups B and C. Overall, HPP, as a pretreatment technology, could accelerate the moisture migration and improve the drying efficiency of VFD process for shrimp. PRACTICAL APPLICATION: High pressure processing (HPP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, there is limited information about its application in shrimp-drying process and the moisture dynamic of shrimp subjected to high pressure processing-assisted vacuum-freeze drying. This study could provide valuable information regarding the moisture status and migration in HPP-VFD shrimp monitored by LF-NMR and MRI methods. The results showed that HPP processing at 550MPa for 10min can be used as an interesting method for drying pretreatment, increasing its drying rate and consequently reducing its process time, and it demonstrated that the methods used in this study had good correlation coefficient with physicochemical properties of shrimp, which may be real-time and nondestructive monitoring methods for shrimp-drying process.