High Hydrostatic Pressure Treatment Research Articles

Effect of high-hydrostatic-pressure processing on catechin content in green tea leaves

ABSTRACT Green tea catechins can improve human health, and their retention during processing is a concern. High hydrostatic pressure (HHP) blanching is a nonthermal processing that can increase both nutrients and flavor in tea. Thermal blanching retains catechins but decreases nutrients and flavor. We investigated catechin retention potency via HHP and thermal treatment. Fresh green tea leaves were pressurized at 100–800 MPa and/or heated for 10 min at 40°C–70°C and then stored for 24 hours. Tea catechin content was drastically reduced after storage without HHP, which yielded a 1.5–8.0-fold increase. HHP showed a smiling curve relationship with catechin retention, with the highest levels found at 200 and 800 MPa. Synergistic effects of HHP on thermal processing were found at 40°C–50°C but not at 60°C–80°C. Processing at 200 MPa combined with 50°C yielded 88% catechin retention. Our results suggest this combination as an optimal strategy for retaining tea catechins, nutrients, and flavor.

Vacuum impregnation of liquid into carrot assisted by high hydrostatic pressure

ABSTRACT Carrot was impregnated with pigment solution by vacuum heat sealing (VS) and/or high hydrostatic pressure treatment (HHP; 100–600 MPa, 25°C, 5 min). Impregnation efficacy was evaluated as impregnation ratio (%) by image analysis, while damages of cell membrane and texture were quantified by electrical impedance spectroscopy and texture analysis, respectively. Combinations of VS and HHP exclusively achieved 100% impregnation. Meanwhile, the damages were comparable between the samples after VS and VS + 100 MPa treatment and aggravated by elevated levels of HHP. As for the texture, breaking stress (hardness) decreased after VS and VS + HHP (100–600 MPa) comparably. Meanwhile, breaking strain (deformability) significantly increased after VS + HHP (200–600 MPa), indicating further damage of strain texture as compared with that after VS and VS + 100 MPa treatments. It was indicated that impregnation of carrot was fully achieved by a combination of VS and 100 MPa treatment, while minimizing the cell membrane and texture damages. Difference in the impregnation efficacy between carrot and apple was discussed based on their image data.

Effect of high hydrostatic pressure and ultrasonic treatment on solubility and structural changes of rice bran protein

SummaryThe effect of non‐thermal treatment on the solubility and structural properties of rice bran protein was investigated. It was shown that the non‐thermal treatment significantly improved the solubility of rice bran protein, in which, HHP and US increased it by 76.69% and 136.75%, respectively. The structural analysis showed that the non‐thermal treatment reduced the β‐sheet content and increased the content of free sulfhydryl groups on the surface, indicating that the inter‐chain hydrogen and disulfide bonds of rice bran protein were broken and the protein structure shifted from order to disorder. And the internal chromogenic groups of the protein were exposed and tended to the hydrophilic environment, indicating the exposure of hydrophilic groups. This study provides a theoretical basis for non‐thermal modification of rice bran protein and its processing and utilisation.

Effect of UV-C Irradiation and High Hydrostatic Pressure on Microbiological, Chemical, Physical and Sensory Properties of Fresh-Cut Potatoes

UV-C irradiation and high hydrostatic pressure (HHP) successfully reduce the number of bacteria and their growth but can also affect phenolic and sugar content, as well as other physicochemical properties. Therefore, in this work, the effect of UV-C irradiation, HHP, and their combination, UV-C/HHP, on total aerobic mesophilic bacteria count (TAMBC), chlorogenic acid and sugar content, and other physicochemical properties of raw FCP were examined. Acrylamide and polycyclic aromatic hydrocarbons (PAH) were also monitored in treated FCP after frying. Vacuum-packed potato slices pretreated with an antibrowning agent were irradiated with UV-C (2.70 kJ m−2), treated with HHP (400 MPa/3 min) and combined UV-C/HHP, and stored for 15 days. The greatest reduction in TAMBC was achieved in the UV-C/HHP-treated samples, followed by the HHP treatment, and they both resulted in the slowest bacterial growth during storage. All treatments decreased the contents of chlorogenic acid, but the greatest reduction was observed in the HHP-treated samples. All treatments increased the content of reducing sugars, and UV-C/HHP did so significantly, which also led to an increase in acrylamide content in the fried FCP. PAH levels were below the established limits. Acceptable sensory attributes of all samples (raw, boiled, and fried) remained relatively stable during storage.

Effect of High Hydrostatic Pressure Processing on the Microbiological Quality and Bacterial Diversity of Sous-Vide-Cooked Cod

High hydrostatic pressure (HP) is a promising method to improve the microbiological quality of sous-vide foods. Monitoring the composition and behavior of the microbial communities in foods is of most importance for the production of high-quality and safe products. High-throughput sequencing (HTS) provides advanced approaches to determine food's microbial community composition and structure. The aim of the present study was to determine the impact of different HP treatments on the microbial load and bacterial diversity of sous-vide Atlantic cod. Sous-vide cooking at 57.1 °C for 30 min followed by HP treatment at 500 MPa for 8 min reduced viable cell counts (total aerobic mesophiles) in the cod samples below detectable levels for 45 days of storage under refrigeration. In a second trial with cod cooked sous-vide at 52 °C for 20 min followed by HP treatments at 300 or 600 MPa (with HP treatment temperatures of 22 °C or 50 °C for 4 or 8 min, depending on treatment), only the treatments at 600 MPa delayed bacterial growth for at least 30 days under refrigeration. The optimal HP conditions to improve the microbiological quality of sous-vide cod cooked at low temperatures were obtained at 600 MPa for 4 min at a pressurization temperature of 50 °C. Bacterial diversity was studied in cod cooked sous-vide at 52 °C for 20 min by HTS. In the absence of HP treatment, Proteobacteria was the main bacterial group. A succession of Pseudomonadaceae (Pseudomonas) and Enterobacteriaceae was observed during storage. Firmicutes had low relative abundances and were represented mainly by Anoxybacillus (early storage) and Carnobacterium (late storage). The HP-treated sous-vide cod showed the greatest differences from controls during late storage, with Aerococcus and Enterococcus as predominant groups (depending on the HP conditions). The application of HTS provided new insights on the diversity and dynamics of the bacterial communities of sous-vide cod, revealing the presence of bacterial genera not previously described in this food, such as Anoxybacillus. The significance of Anoxybacillus as a contaminant of seafoods should be further investigated.

High hydrostatic pressure (HHP) as a green technology opens up a new possibility for the fabrication of electrospun nanofibers: Part I- improvement of soy protein isolate properties by HHP

A common problem of electrospinning of plant proteins is that these kinds of proteins, including soy protein isolate (SPI), should be highly soluble and preferably in a random coil structure rather than the globular conformation. The current solution is to apply thermal treatment; however, it results in extensive organoleptic consequences (e.g. color degradation and off-flavor) and loss of nutrients. Thus, if a non-thermal technology such as high hydrostatic pressure (HHP) increases the disordered structure of the protein, it could facilitate the electrospinning of the protein and eliminate the barriers of thermal treatment, forming our hypothesis in this research. To this end, initially, extensive experiments including protein solubility, sulfhydryl content, turbidity, surface hydrophobicity, circular dichroism, and viscosity tests were carried out on HHP (200, 400 and 600 MPa) and thermally treated SPI samples (3.5% and 7% w/w). The results of sulfhydryl content revealed that disulfide bonds decreased at 400 MPa more intensely than other pressures while surface hydrophobic forces were promoted at this pressure. The circular dichroism test results showed that HHP treatment resulted in higher disordered structures and lower ordered ones, which is particularly helpful for the electrospinning process; besides, lower β-sheet content achieved by HHP treatment is especially useful for attaining defect-free fibers. For the first time, in this research, ideal electrospun fibers with average diameters of 300–400 nm were achieved through HHP processing, without using any thermal energy.

Effect of high pressure processing on gastrointestinal fate of carotenoids in mango juice: Insights obtained from macroscopic to microscopic scales

High hydrostatic pressure (HHP) and high-pressure homogenization (HPH) were applied to mango juice to explore their effects on gastric retention rate (G-CRR), bioaccessibility (BAC) of total and individual carotenoids, and the corresponding mechanisms from macroscopic to microscopic scales. Compared to the control, both HHP and HPH at 50 MPa had no significant effect on BAC and G-CRR, whereas HPH at 100 MPa significantly increased BAC by 44.33% and G-CRR by 11.84%. Further HHP treatments (particularly at 400 MPa) on the 100 MPa-HPH-pretreated samples significantly increased BAC by 71.37% and G-CRR by 24.24%. Violaxanthins/esters were less stable than carotenes in the stomach, resulting in lower bioaccessibility of violaxanthins/esters. G-CRR and BAC were negatively correlated with the viscosity and particle size of juice, whereas they were positively correlated with the solubility/dispersibility of carotenoids. In addition, pectin-carotenoid interactions may also be an important factor affecting the digestive fate of carotenoids in juice. Industrial relevanceHigh pressure processing (High hydrostatic pressure, HHP, and high pressure homogenization, HPH) is a non-thermal technique and its effect on the bioaccessibility of carotenoids in fruits and vegetables have attracted attention from researchers. Our research found that HPH and HHP combined treatment could decrease the particle size of mango juice, and increase the viscosity and turbidity as well as the bioaccessibility of carotenoids therein. This technology can be used to preserve the physical stability of mango juice and improve the nutritional value.

High hydrostatic pressure (HHP) reinforces solid encapsulation of d-limonene into V-type starch and its application in strawberry storage

The formation of inclusion complexes (ICs) between V-type starch and flavors is traditionally conducted in an aqueous system. In this study, limonene was solid encapsulated into V6-starch under ambient pressure (AP) and high hydrostatic pressure (HHP). The maximum loading capacity reached 639.0 mg/g after HHP treatment, and the highest encapsulation efficiency was 79.9 %. X-ray Diffraction (XRD) results showed that the ordered structure of V6-starch was ameliorated with limonene, which avoided the reduction of the space between adjacent helices within V6-starch generated by HHP treatment. Notably, HHP treatment may force molecular permeation of limonene from amorphous regions into inter-crystalline amorphous regions and crystalline regions as the Small-angle X-ray scattering (SAXS) patterns indicated, leading to better controlled-release behavior. Thermogravimetry analysis (TGA) revealed that the solid encapsulation of V-type starch improved the thermal stability of limonene. Further, the release kinetics study showed that a complex prepared with a mass ratio of 2:1 under HHP treatment sustainably released limonene over 96 h and exhibited a preferable antimicrobial effect, which could extend the shelf life of strawberries.

Influence of pressurization rate and mode on cell damage of Escherichia coli and Staphyloccocus aureus by high hydrostatic pressure

As a non-thermal technology, high hydrostatic pressure (HHP) has been widely investigated for inactivating microorganisms in food. Few studies have been presented on the pressurization/depressurization rate and mode of microbial inactivation. In this study, effect of pressurization rate and mode on Escherichia coli and Staphylococcus aureus cell damage during HHP treatment was investigated. The results showed that fast pressurization + linear mode (FL) treatment has the best bactericidal effect on E. coli and S. aureus, followed by fast pressurization + stepwise mode (FS) and slow pressurization + stepwise mode (SS) treatments. FL treatment caused more morphological damage to the cell wall, cell membrane, and cytoplasmic components compared with FS and SS treatment detected by SEM and TEM. Additionally, the damage to membrane permeability of them was also enhanced after FL treatment. Therefore, our results indicated that FL treatment could be applied to enhance the bactericidal effect of HHP on bacteria by increasing the damage to cell morphological structure and membrane integrity.

Effects of high hydrostatic pressure treatment on the antigenicity, structural and digestive properties of whey protein

The effects of high hydrostatic pressure (HHP) treatment and in vitro simulated infant digestion on the antigenicity of whey protein concentrate (WPC) were investigated. The results revealed that the greatest decline in allergenicity was observed at 500 MPa for 10 min, which was 76.19% ± 1.45%. HHP treatment (500 MPa/10 min) contributed to WPC structure stretched as β-sheet content increased from 18.45% ± 0.32%–20.93% ± 0.59% (p < 0.05). Fluorescence spectroscopy indicated the fluorescence intensity increased from 4.649 × 106 to 5.205 × 106 with the increased HHP time (0–15 min). There was a 1.39-fold increase in hydrophobicity of HHP-modified WPC which was the equilibrium result of protein unfolding and intermolecular aggregation. HHP treatment (500 MPa/10 min) facilitated the conformational changes of WPC that were needed to increase the effectiveness of in vitro simulated infant digestion, and increased the content of peptides with molecular weights below 10,000 Da in digestion products by 9.99%. HHP pretreatment prior to in vitro simulated infant digestion reduced the retention of WPC antigenicity to the lowest level, which was 38.96%. Overall, this study suggests that appropriate HHP treatment could be a promising technique to improve the digestibility of milk proteins and reduce their antigenicity.

Quality and flavor changes in beef jerky caused by high hydrostatic pressure combined with moisture regulator treatments during storage

The impact of high hydrostatic pressure (HHP) combined with moisture regulators (MR) on the quality and flavor attributes of beef jerky during storage was investigated in this study. During storage, moisture content decreased in all the treatments, and it was significantly higher in MR + HHP samples than in HHP and control samples (<i>P</i> &lt; 0.05). At 0 and 15 days, the water activity was approximately 0.7, and at 60 days, it decreased to 0.652 for control samples and 0.678 for MR + HHP samples. During storage, the MR + HHP samples had lower shear force and thiobarbituric acid reactive substances (TBARs) value than the control and HHP samples (<i>P</i> &lt; 0.05). MR + HHP increased the formation of volatile compounds derived from spices while inhibiting the formation of volatile compounds derived from lipid oxidation. The sensory scores of MR + HHP samples for tenderness, color, taste, and flavor were significantly higher than that of the HHP and control samples (<i>P</i> &lt; 0.05). This study revealed that HHP and MR treatment reduced the quality deterioration of beef jerky during storage.

Crystal structure changes of native and retrograded starches modified by high hydrostatic pressure: Physical dual modification

The effect of high hydrostatic pressure (HHP) on the structural changes of starches with different state of organization was investigated. Starch in native state (granular - NS) and in retrograded state (granular structure not present - RetS) were adjusted to 40% (w/v) of moisture and then treated at pressures of 300 and 600 MPa for 5 min at 10 °C. The structural changes of NS and RetS were significantly and differently affected by the HHP treatment. When the pressure increased, orthorhombic unit cell of NS showed an increase in crystal parameter of c-axis and a decrease of a- and b-axes. Crystallinity, crystallite size, short-range ordered structure (DO), organization of the double helix structures (DD), and enthalpy change (ΔH) gradually decreased. After treatment at 300 MPa, the granules get aggregated while keeping their granular structure, promoting a higher viscosity. At 600 MPa, leached material, aggregated granules, destroyed, and with collapsed “ellipsoid-shape” structure were observed, which contributes to decreasing the viscosity. In RetS, the dual physical modification achieved after pressurizing the hydrothermally treated starch, resulted in a significant increase in the crystal parameters (a, b, and c) of hexagonal unit cell. Furthermore, the crystallinity, crystallite size, DD, DO, ΔH, and viscosity were improved, while a gradual decrease of the amounts of cavities was observed. Crystal structure changes in RetS showed that the double helices of unit cell were stabilized by dual modification, while the unit cell was affected after pressurization of NS. This investigation is the first evidence of the application of HHP on RetS.

The metabolome of human milk is altered differentially by Holder pasteurization and high hydrostatic pressure processing.

The milk metabolome is composed of hundreds of molecules that can impact infant development. In preterm infants, sterilized donor milk (DM) is frequently used for their feeding. We aimed to identify differences in the metabolome of DM after two types of milk sterilization: the Holder pasteurization (HoP) and a high hydrostatic pressure (HP) processing. DM samples were sterilized by HoP (62.5°C for 30 min) or processed by HP (350 MPa at 38°C). 595 milk metabolites were analyzed using an untargeted metabolomic analysis. Both treatments differentially altered several classes of compounds. The major changes noted included decreased levels of free fatty acids, phospholipid metabolites, and sphingomyelins. Decreases were more strongly noted in HP samples rather than in HoP ones. Both HoP and HP treatments increased the levels of ceramides and nucleotide compounds. The sterilization of human milk altered its metabolome especially for lipids.

In vitro gastrointestinal model for the elderly: Effect of high hydrostatic pressure on protein structures and antioxidant activities of whey protein isolate

With the increase in global life expectancy, the research on the specific digestive patterns of the elderly is becoming highly essential. We simulated the digestion process of older individuals in vitro and investigated the effects of various high hydrostatic pressure (HHP) treatments on the protein structure, digestibility, and antioxidant activity of whey protein isolate (WPI), as well as the antioxidant peptides produced from its digest. The HHP treatment specifically affected on the secondary and tertiary protein structures along with the free sulfhydryl content of WPI. Protein microstructure revealed a significant increase in the number and depth of pores. Highest in vitro digestibility and cellular antioxidant activity was observed after HHP treatment at 600 MPa for 30 min. In the intestinal digest, 15 antioxidant peptides were identified whose characteristics matched those of bioactive peptides. Of these, the LGSDMEDLR peptide sequence had the highest "-CDOCKER Energy” and formed the salt bridge, attractive charge, conventional hydrogen bond, carbon hydrogen bond, and van der Waals with Arg380, Arg415, Arg483, Tyr334 and Asn382, which all located in the binding site of the Keap1-Nrf2 interaction. Overall, HHP appeared to be a potential method for the application of dairy products among the elderly.

Influences of high hydrostatic pressure on structures and properties of mung bean starch and quality of cationic starch

It is difficult to improve the quality of chemical-modified starch by traditional technology. Hence, in this study, mung bean starch with poor chemical activity was used as raw material, the native starch was treated and the cationic starch was prepared under high hydrostatic pressure (HHP) at 500 MPa and 40 °C. By studying the changes in the structure and properties of native starch after HHP treatment, the influence mechanism of HHP on improving the quality of cationic starch was analyzed. Results showed high pressure could make water and etherifying agent enter the starch granules through pores, and HHP made the structure of starch undergone three stages similar to mechanochemical effect. After HHP treated for 5 and 20 min, the degree of substitution, reaction efficiency and other qualities of cationic starch increased remarkably. Hence, proper HHP treatment could help to improve the chemical activity of starch and quality of cationic starch.

High Hydrostatic Pressure Treatments Improved Properties of Fermentation of Apple Juice Accompanied by Higher Reserved Lactobacillus plantarum.

This study aimed to assess the feasibility of high hydrostatic pressure (HHP) treatment to obtain high quality juice, and prepared functional apple juice using fermentation technology. The physicochemical properties of HHP (10 min) pasteurized and pasteurized (85 °C, 15 min) apple juices were compared during fermentation. Moreover, the survival of Lactobacillus plantarum after fermentation under simulated gastrointestinal conditions was evaluated. Results showed that HHP-treated apple juice had better properties than that of pasteurized in terms of color difference, total phenol content, and antioxidant activity. After fermentation, about 2.00 log CFU/mL increase in viability of cells was observed and there was around 0.8 reduction in pH value, and the antioxidant capacities were also significantly improved. Additionally, the content of caffeic acid, ferulic acid, and chlorogenic acid significantly increased after 24 h of fermentation. The survival of Lactobacillus plantarum in simulated gastric fluid reached 97.37% after fermentation. Overall, HHP treatment is expected to be a substitute technology to pasteurization in order to obtain higher quality fermented fruit juice. This study could also be helpful for exploitation of fermented juice.

Effect of Vacuum Impregnation and High Hydrostatic Pressure Treatments on Shelf Life, Physicochemical, and Sensory Properties of Seabream Fillets

Marination is commonly used to preserve fish, which, in combination with other non-thermal technologies, such as vacuum impregnation and high hydrostatic pressure, may help to preserve freshness and extend shelf life. In addition, marination may mask changes in physicochemical properties and the sensory attributes of fish resulting from intense pressurization treatments. In this study, we evaluated the effects of vacuum impregnation (50 mbar for 5 min) alone or in combination with a moderate pressurization treatment (250 MPa for 6 min) on the physicochemical properties, microbiological and oxidative stability, and sensory properties of refrigerated seabream fillets. Compared to conventional marination, vacuum impregnation alone had no effect on the aforementioned properties, except for a higher perception of lemon aroma (0.9 vs. 1.6). However, vacuum impregnation with pressurization reduced the total viable mesophilic aerobic bacteria to counts below 4 log colony forming units (CFU)/g after 16 days of storage at ≤ 2 °C, compared to 6 log CFU/g with conventional marination. Additionally, the color and texture were affected by the pressurization treatment. However, color was more susceptible, and at the beginning of storage, lightness was higher in the pressurized samples than in the control (52 vs. 78). Regardless, this whitening effect and other minor changes in texture and sensory properties compared to conventional marination with vacuum impregnation with pressurization can be considered of little relevance considering the increase in shelf life, the lack of lipid oxidation (maintained at low and similar levels as those of the non-pressurized samples), and the intrinsic whitening effects of certain marinades.

Physicochemical Properties of Soft and Hard-type Rice Flour According to Moisture Content and High Hydrostatic Pressure Treatment

This study investigated the effects of high hydrostatic pressure (HHP) treatment on the physicochemical properties of rice flour according to its moisture levels in order to develop new materials for processed rice foods. The rice varieties used were the Samkwang variety (normal and hard type) and the Shingil variety (processing and soft type). The moisture content of the rice flour was adjusted to 35-55% and it was treated with the HHP treatment at 400-600 MPa. The water absorption capacity, solubility, and swelling power of the rice flour increased as the moisture levels and pressure increased. The 600 MPa enzymatic hydrolysis-treated rice flour showed similar results to the heat-treated rice flour. Scanning electron microscopy showed few cavities, resulting in a dense structure. X-ray diffraction confirmed that the 23° peak, which indicates the degree of gelatinization, decreased with increasing moisture levels and pressure. The HHP treatment of the rice flour changed its physicochemical properties according to the moisture levels and pressure applied. These results can provide important information on the development and production of various foods.

Effects of high hydrostatic pressure treatment on bacterial composition in donkey milk studied by high throughput sequencing

High hydrostatic pressure has become a non-thermal alternative to thermal pasteurization in dairy product processing. In this study, we investigated the effects of the treatment of high hydrostatic pressure on the bacterial composition in donkey milk using high-throughput sequencing technology and culture-dependent methods. Compared with the microbial composition in the untreated donkey milk, the relative percentage of <italic>Pseudomonas</italic> and <italic>Acinetobacter</italic> in donkey milk after high hydrostatic pressure was significantly decreased by 4.92% and 4.82%, respectively. Beta diversity analysis demonstrated that the treatment of high hydrostatic pressure affected the microbial composition in donkey milk significantly. The potential probiotic <italic>Enterococcus casseliflavus</italic> isolated from the untreated donkey milk has a good acidifying ability. This study revealed the effects of high hydrostatic pressure treatment on the microbial composition in donkey milk, exhibiting its practical industrial application and the potential use of biological resources in the future.

Effects of high hydrostatic pressure on physicochemical and functional properties of soybean protein isolate

Impacts of high hydrostatic pressure (HHP) pretreatment on the physicochemical, functional and antioxidant properties of soybean protein isolate (SPI) were investigated. Changes in the secondary and tertiary structures were determined by Fourier transform infrared spectra and fluorescence spectra. The particle sizes reduced from 217.20 nm to 192.70 nm while the zeta potential increased. It’s revealed by scanning electron microscopy that the HHP treatment could result in the formation of large aggregation, leaving the SPI with irregular and uneven surface. Moreover, hollow spheres were also observed in SPI by means of dynamic and static light scattering. As a result, the foaming capacity of HHP-treated SPI and antioxidant activity of the HHP-treated SPI hydrolysates were improved significantly.