High Hydrostatic Pressure Pretreatment Research Articles

Immobilization of iron-loaded niosomes within electrospun nanofibers of soy protein isolate: A novel dual encapsulation technique

In this research, a dual encapsulation system was developed for loading niosomes into electrospun nanofibers of soy protein isolate (SPI)-polyvinyl alcohol (PVA); high hydrostatic pressure (HHP) was also applied to reinforce the nanofibers. For this purpose, different samples with various levels of HHP-treated SPI, PVA, and iron niosomes were prepared. Encapsulation efficiency as well as the bioavailability of iron increased in HHP-treated samples because HHP was able to disassemble the structure of the base polymers (SPI-PVA), allowing the iron to load into the skeleton of the base polymer and, consequently, encapsulated it in the structure strictly and suitably. HHP resulted in a higher transformation and bioavailability of SPI:PVA fibers, which is due to the destruction effect of this pretreatment on SPI and neutralizing its inhibitory effect. HHP eventuated lower Atomic Force Microscopy (AFM) indices in nanofibers because it can cause denaturation and aggregation of proteins, resulting in a more compact and homogeneous protein network. The results of this study are useful as a practical guide on how to prepare niosome-embedded SPI nanofibers (especially for the enrichment of plant-based nanofibers), what their properties are, and how to improve their characteristics through HHP pretreatment.

Effect of high hydrostatic pressure pretreatment on physicochemical properties, bioactive components and antioxidant activities of dehydrated yam slices

High hydrostatic pressure (HHP) treatment has been widely used to achieve the desired safety and quality of food products during the past two decades. In this work, effects of HHP (100–600 MPa) pretreatments on physicochemical properties, bioactive components and antioxidant activities of dehydrated yam slices were studied. The results indicated that HHP pretreatments dramatically improved the hardness, crispness, integrity ratio, and total color change of the dehydrated yam slices, while significantly inhibited their rehydration ratio when the pressure was ≥200 MPa. According to the results of scanning electron microscopy (SEM), optical microscopy (OM), and polarized optical microscopy (POM), HHP could induce the indentations and cracks of partly starch granules surface, but without any starch gelatinization. Compared with the control sample, higher total polyphenols compounds (TPC) and allantoin content were observed in the HHP pretreated samples, and the 200 MPa pretreated sample had the highest TPC and allantoin which reached 0.45 mg GAE/g and 5.47 mg/g dry weight, respectively. Furthermore, the antioxidant analysis showed that 100 and 200 MPa pretreatment could effectively enhance the antioxidant capacity of the yam slices. The above results suggested that HHP pretreatment, especially under 200 MPa, could be an appropriate assist for preparation of high-quality dehydrated yam slices.

Effects of different temperatures on electric oven drying of myrtle (Eugenia gracillima Kiaersk.) seeds modified by High Hydrostatic Pressure (HHP)

The objective was to evaluate the effects of different temperatures (50, 60, and 70 °C) on electric oven drying of Eugenia gracillima Kiaersk. seeds modified by High Hydrostatic Pressure (HHP). All models tested (Lewis, Page, Handerson and Pabis, and Silva et alii) showed R2 above 0.97 and X2 below 0.05, with better fits using Page's model. HHP pre-treatment caused higher thermal resistance in a short time, and lower starch and amylose content, although these polysaccharides increased with increasing drying temperature. At the morphological level, the pre-treated seeds were described as having uneven, wrinkled, deformed, and more brittle surfaces. The seeds were identified for the first time with major contents of magnesium, calcium, and iron. The association of thermal and non-thermal technologies proved to be satisfactory and promising for application in this by-product, encouraging the development of new food products for human or animal consumption.

Biotransformation of wheat proteins with Lactobacillus sp. following high hydrostatic pressure pre-treatment to reduce gluten immunoreactivity

The effect of high hydrostatic pressure (HHP, 50–300 MPa, 5 min, 18 °C) on the biotransformation of wheat proteins with Lactobacillus acidophilus or L. sanfranciscensis was studied. Increasing the pressure from 50 to 150 MPa before sourdough fermentation did not change the size of the bacterial population, but it increased the endoproteolytic activity of Lactobacillus enzymes, degree of protein hydrolysis and decreased the concentration of gliadins and gluten immunoreactivity. Fermentation after pressurization at 150 MPa reduces to 44.0 ± 0.1 and 25.6 ± 1.1%, the immunoreactivity of proteins in sourdough obtained by fermentation with L. acidophilus and L. sanfranciscensis, respectively. Further increasing the pressure from 150 to 300 MPa resulted in the reduction of bacterial growth, reduction of endoproteolytic activity, degree of protein hydrolysis, gliadin degradation and gluten immunoreactivity. Sourdough treatment at 250 and 300 MPa increased the antigen concentration compared to the control samples. The fermentation of sourdough with L. acidophilus and L. sanfranciscensis, following increasing pressurization, resulted in an increase in the β-sheets and a decrease in the α-helix structure of the protein. Applying the pressure of 250 and 300 MPa changes the conformation of gluten, and reduced significantly activity of peptidases of Lactobacillus strains, thereby increasing protein immunoreactivity.

Role of high hydrostatic pressure pretreatment on the formation of electrospun nanofibers from soy protein isolate/polyvinyl alcohol

In this research, the characteristics of the high hydrostatic pressure (HHP)-treated soy protein isolate (SPI) solutions as well as HHP-treated SPI (HSPI) electrospun fibers were comprehensively studied for the first time. For this purpose, surface tension, electrical conductivity, viscosity, zeta potential, and secondary structure of HSPI solutions at different ratios were investigated. Also, differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) of HHP-treated and non-treated SPI: PVA nanofibers were thoroughly compared. HHP denaturation reduced the size of nanofibers by 50–100 nm, diminished ordered structures and crystallinity of nanofibers, increased their melting point and induced hydrogen bonding between amino groups of denatured SPI and hydroxyl groups of PVA. These findings open a new horizon in the successful application of non-thermal energies in the electrospinning process to achieve appropriate fibers at nanoscale.

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.

Insights into high hydrostatic pressure pre-treatment generating a more efficient catalytic mode of maltogenic α-amylase: Effect of multi-level structure on retrogradation properties of maize starch

Maltogenic α-amylase (MA) is an enzyme used to retard starch retrogradation in the baking industry. However, sometimes it exhibits low efficiency which may restrict the enzymatic application. This study investigates the effects of using High hydrostatic pressure (HHP) as a pre-treatment to promote MA catalysis. The results showed that HHP resulted in more indentations and fissures of the starch granules promoting the susceptibility of MA. While MA treatment alone introduced short malto-oligosaccharide chains with degree of polymerization (DP) 1–5, the combined HHP-MA treatment exhibited a higher proportion of DP 1–9, but a lower proportion of DP 13–24. Furthermore, when increasing the pressure, the ratio of α-1,6 to α-1,4 glycosidic bonds increased in the MA-treated starch. MA modification on the HHP-pretreated starch showed increasing gelatinization temperature and enthalpy, while it had a reverse impact on long-term retrogradation enthalpy due to the shortening of the outer chains of amylopectin. LF-NMR was applied to analyze the water mobility and compartmentalization in starch gel systems after 1- and 7-days storage. Compared with single MA-treated system, HHP-MA treated starches showed no significant changes in the value of the transverse relaxation times, but less amount of bulk water was detected due to higher amounts of soluble small oligosaccharides. In conclusion, HHP pre-treatment combined with MA could improve the water holding properties of retrograded starch gels and that HHP prior to MA catalysis provides an efficient alternative method to modify starch-based food products with anti-stalling properties.

Exploring the hydration promotion and cooking quality improvement of adlay seed by high hydrostatic pressure

Adlay (Coix lacryma-jobi L. var. ma-yuen Stapf), a minor cereal, has long been consumed as both a food and a medicine. However, adlay seeds have a dense episperm and its tissue is hard, which makes water absorption difficult. High hydrostatic pressure (HHP), as a non-thermal processing technology, enables batch hydration of grains in a short time. In this work, the hydration promotion and cooking quality improvement of adlay seeds by HHP (300–600 MPa) were investigated. Results showed that HHP pretreatment promoted seed hydration by inducing cracks in the seed cross-section and disrupting the cell wall and ventral groove structure. HHP pretreatment increased the proportion of intracellular water and unbound water in the cooked adlay seeds, facilitated water infiltration from the seed grooves and increased the hydration rate by creating a water gradient between the soak water and seeds. After applying HHP during soaking, the cooking time of adlay seeds was reduced, and the cooked adlay seeds were softer, brighter in color.

Effects of cold plasma, high hydrostatic pressure, ultrasound, and high-pressure carbon dioxide pretreatments on the quality characteristics of vacuum freeze-dried jujube slices

Pretreatment combined with vacuum freeze-drying is an effective technique to extend the storage period of jujube fruits and reduce energy consumption and cost; however, the effects of pretreatment on the quality characteristics of jujube during vacuum freeze-drying remain unknown. In this study, the effects of cold plasma (CP), high hydrostatic pressure (HHP), ultrasound (US), high-pressure carbon dioxide (HPCD), and conventional blanching (BC) as pretreatments on the performance of vacuum freeze-dried jujube slices were investigated. The results indicated that the application of different pretreatments decreased the water activity and increased the rehydration capacity, owing to the pretreatment etching larger and more porous holes in the microstructure. Freeze-dried jujube slices pretreated with HPCD retained most of their quality characteristics (color, hardness, and volatile compounds), followed by the HHP- and US-pretreated samples, whereas samples pretreated with BC showed the greatest deterioration in quality characteristics, and hence, BC is not recommended as a pretreatment for freeze-dried jujube slices. Sensory evaluation based on hedonic analysis showed that jujube slices pretreated with HPCD and US were close to the control sample and scored highest. Compared to other pretreated samples and the control, freeze-dried jujube slices pretreated with HPCD showed the least degradation (4.93%) of cyclic adenosine monophosphate (cAMP), the highest contents of total phenol, total flavonoid, and l-ascorbic acid, and the highest antioxidant capacity. Partial least squares-discriminant analysis (PLS-DA) was performed to screen all the quality characteristic data of different pretreated samples, and 12 volatile compounds, including ethyl hexanoate and (E)-2-hexenal, along with color, l-ascorbic acid content, and cAMP content were found suitable to be used as discriminators for pretreated freeze-dried jujube slices. Therefore, non-thermal pretreatments, including HPCD, US, and HHP pretreatments, are promising techniques for the vacuum freeze-drying of jujube products.

Sustainable extraction of polyphenols from millet using switchable deep eutectic solvents

In this study, polyphenols were extracted from millet with a high hydrostatic pressure (HHP) pretreatment combined with switchable deep eutectic solvent (DES) extraction. The antioxidant activity of the extract was evaluated, and the switchable DESs were recycled and reused. HHP pretreatment destroyed the cell structure of millet to facilitate the extraction of polyphenols. The grinding-assisted extraction was used as the extraction method by taking switchable DES (octanoic acid-linalool) as the extraction solvent and β-cyclodextrin as the auxiliary extraction reagent. The hydrophilic DES was switched to the hydrophobic DES to recover millet polyphenols. The hydrophobic DES was recycled and switched to the hydrophilic DES for extracting new millet samples. After being reused five times, the yield of millet polyphenols using recycled DESs did not decrease significantly. In conclusion, HHP pretreatment combined with switchable DES extraction is considered as a green, efficient, and sustainable method for bioactive compounds.

Effect of high pressure pretreatment on myrosinase-glucosinolate system, physicochemical and bacterial properties during fermentation of brine-pickled radishes

The myrosinase-glucosinolate system, physicochemical properties, and bacterial community were profiled during fermentation of high hydrostatic pressure (HHP) pretreated brine-pickled radishes; traditionally brine-pickled radishes were utilised as the control. Scanning electron microscopy (SEM) analysis revealed that 300 MPa pretreatment promoted brine infiltration in radish cells and damaged cellular microstructures, which activated the myrosinase-glucosinolate system. The conversion of glucosinolate (GLs) to isothiocyanates (ITC) increased and significantly enhanced the raphasatin and sulforaphene contents of pickled radish. However, 600 MPa pretreatment suppressed myrosinase activity. HHP pretreatment altered the natural radish bacterial communities by reducing the total bacterial and lactic acid bacteria counts. Lactobacillus spp. became the dominant bacterial genus within 15 d of fermentation. However, the destruction of cellular structures by HHP pretreatment also significantly decreased hardness and caused the dissolution of amino acids and TTA into brine. This caused reduced amino acid and TTA contents compared to the control group, as well as decreases in pH. HHP pretreatment suppressed the growth of spoilage bacteria (e.g. Pseudomonas, Staphylococcus, and Shewanella genera). This study provides new insight into the potential applications of HHP treatment in pickling, as it demonstrates that HHP can increase the ITC conversion rate of pickled radish, modify its physiochemical characteristics, and decrease microbial risk. Therefore, HHP is a promising preprocessing technique to be used for pickle manufacturing industry.

Effect of high hydrostatic pressure on the in vitro development and molecular quality of transgenic rabbit embryos derived from nano-transfected zygotes

Abstract The aim of this study was to evaluate the effect of high hydrostatic pressure (HHP) on the in vitro developmental abilities of nano-transfected rabbit zygotes, their transfection efficiency, and the molecular quality of the blastocysts generated. This quality was assessed by estimating the quantitative profiles of Oct4, Casp7, and Bcl2 mRNA transcripts. The nano-transfection efficiencies of zygotes that had been pre-treated with either 20 MPa or 40 MPa of HHP (13.5% and 13.7%, respectively) were insignificantly lower than those found in zygotes not exposed to HHP prior to their nano-transfection (20.1%; P≥0.05). Moreover, applying HHP treatment with the parameters of 20 MPa and 40 MPa followed by the nano-transfection of zygotes brought about an insignificant decrease in the rates of embryos at the blastocyst stage (30.4% and 23.0%, respectively) as compared to the control group of nano-transfected zygotes (40.4%; P≥0.05). Furthermore, analyzing the transcriptional activity of Oct4, Bcl2, and Casp7 genes revealed that HHP enhances the relative abundance (RA) of all mRNA transcripts in blastocysts derived from non-transfected rabbit zygotes. In turn, the augmented RAs found in the pro-apoptotic Casp7 and anti-apoptotic Bcl-2 transcripts confirmed the onset and progression of programmed cell death in blastocysts developed from nano-transfected zygotes that had undergone HHP pre-treatment. The conceptualization based not only on a novel nano-transfection approach used to genetically modify in vivo-fertilized rabbit zygotes but also on their HHP pre-treatment is elaborated here for the first time, with an emphasis on further investigations aimed at producing transgenic rabbit and other mammalian species embryos by somatic cell cloning.

Effect of high hydrostatic pressure pretreatment on flavour and physicochemical properties of freeze‐dried carambola slices

SummaryRipe carambolas are hard to store and transport, while freeze‐dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze‐drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze‐drying time. This work guides the application of HHP technology for drying food processing.

Effects of High Hydrostatic Pressure Pretreatment on the Functional and Structural Properties of Rice Bran Protein Hydrolysates.

Rice bran protein (RBP) hydrolysis was conducted after high hydrostatic pressure (HHP) pretreatment. The structural and functional properties of HHP-pretreated rice bran protein hydrolysates (RBPH) were investigated. HHP pretreatments were conducted at 100, 200, and 300 MPa; then, enzymatic hydrolysis at atmospheric pressure was performed using trypsin. An RBPH sample that had not been pretreated by HHP was used as a control. Free sulfhydryl (SH) content, SDS-PAGE profiles, high-performance size exclusion chromatography (HPSEC), Fourier transform infrared (FTIR) spectrum, scanning electron microscopy (SEM), intrinsic fluorescence spectrum, solubility, and emulsifying and foaming properties were evaluated. Changes in particle size and ζ-potential were monitored. Compared with the control, the results of solubility, the emulsifying activity index (EAI) and the emulsifying stability index (ESI) increased significantly (p < 0.05) at 200 MPa. The content of free SH increased significantly (p < 0.05) at 100 MPa. FTIR spectrum and fluorescence analysis confirmed the changes in the secondary and tertiary structures. The experimental results indicated that the structural and functional properties of HHP-pretreated RBPH improved.

Influence of high hydrostatic pressure pretreatment on properties of vacuum-freeze dried strawberry slices.

Effects of high hydrostatic pressure (HHP) (50, 100, 150, 200 and 250MPa) pretreatment on water mobility and distribution, drying duration, microstructure, color, cell wall fraction and tissue structure of strawberry slices were investigated. HHP significantly increased water mobility of the strawberry slices, resulting in the reduction of drying duration by 9-24%. As the pretreatment pressure was increased, redness value and anthocyanin content continuously increased, soluble pectin (SBP) content increased and then decreased, while the contents of protopectin (PTP) and cellulose decreased. After the HHP pretreatment, chromoplasts and moisture was distributed more uniformly in the strawberry slices. Microscopy images showed the formation of microscopic holes or channels in the matrix and the breakdown of tissue structure by HHP. Results suggested HHP pretreatment disrupted the integrity of the fresh strawberry which enhanced the drying efficiency and migration of the chromoplasts during the vacuum-freeze drying process.

A strategy for promoting γ-glutamyltransferase activity and enzymatic synthesis of S-allyl-(L)-cysteine in aged garlic via high hydrostatic pressure pretreatments

S-allyl-(L)-cysteine (SAC) is a bioactive compound within garlic. Its level is low since SAC formation is impeded by the cellular structure of garlic. This study investigates the effect of high hydrostatic pressure (HHP) pretreatment on SAC formation in garlic aged at 40 °C for 10 days. Results showed that HHP could enhance γ-glutamyltransferase (γ-GTP) activity, damage the cellular structure of garlic and increase SAC content in aged garlic by about 7–10 times, depending on the processing parameters. HHP processing at 300 MPa for 15 min provided the optimal conditions for enhancing γ-GTP activity (45%) and promoting SAC formation (from 0.51 ± 0.01 to 5.60 ± 0.22 mg/g dry weight). It was also found that HHP could induce the greening and browning of aged garlic. As such, we consider that HHP technology is a promising technique to produce aged black garlic products with higher amounts of bioactive compounds.

Effects of High Hydrostatic Pressure on the Properties of Heat-Induced Wheat Gluten Gels

This study examined the effects of high hydrostatic pressure pretreatment (100–400 MPa) on the properties of heat-induced wheat gluten (WG) gels. The results showed that treatment with pressure higher than 100 MPa significantly increased the strength, water-holding capacity (WHC), non-freezable water (Wnf), and storage modulus (G′) of heat-induced WG gels. When pressure was increased from 100 to 400 MPa, the free SH content of the heat-induced WG gels increased to 23.55 μmol/g protein, and the surface hydrophobicity (H0) increased to 25.36. Fourier transform infrared spectroscopy (FTIR) analysis showed that the β-sheet and random coil content of the WG treated by high-pressure increased with pressure, while the α-helix and β-turn content decreased. Scanning electron microscopy (SEM) showed that the heat-induced WG gels had more uniform and dense three-dimensional networks after high-hydrostatic-pressure pretreatment.

Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes

High hydrostatic pressure (HHP) and electrodialysis with ultrafiltration membranes (EDUF) are two efficient technologies used respectively to improve protein enzymatic hydrolysis and recovery of bioactive peptides, but they have never been tested together. Hence, in this study, HHP pre-treatment was performed on defatted flaxseed protein isolate prior to enzymatic hydrolysis and the resulting peptides were separated by EDUF. HHP pretreatment influenced particle size, protein conformation, and degree of hydrolysis. After EDUF separation, peptide fractions (generated after enzymatic hydrolysis of control and pressure-treated protein isolate) recovered in KCl fraction were enriched in arginine and associated with a decrease in systolic blood pressure (SBP) in spontaneously hypertensive rats. Additionally, the final EDUF hydrolysate generated from pretreated protein and the initial EDUF hydrolysate from native protein were also associated with lower SBP. However, only the control KCl fraction obtained from native protein hydrolysate was associated with anti-diabetic activity.

Effects of different pretreatments on pumpkin (Cucurbita pepo) lignocellulose degradation

The efficiency of enzymatic hydrolysis is reduced by the naturally recalcitrant complex polymers comprising lignocellulose. Increasing enzymatic conversion, which the complex macromolecules converted into simpler molecules, is still had to be overcome. High hydrostatic pressure (HHP), an emerging technology, is expected to ameliorate the situation. The effects of enzymatic hydrolysis after HHP pretreatment on pumpkin lignocellulose were studied and compared with hydrothermal and alkaline pretreatment. Further investigation was performed to evaluate the effect of enzymatic hydrolysis of pumpkin combined with HHP treatment. The samples underwent HHP treatment simultaneously exhibited overall better performance in enzymatic hydrolysis than the untreated. The highest glucose yield of 91.2% and xylose yield of 84.2% was achieved when 400 MPa HHP with high enzyme loading was applied. HHP exerted positive effects on enzyme-substrate interactions during the enzymatic hydrolysis of lignocellulose, which implied that HHP technology combined with enzymatic hydrolysis could be used to pretreat pumpkin pomace.

Mild high hydrostatic pressure pretreatments applied before soaking process to modulate wholegrain brown rice germination: An examination on embryo growth and physicochemical properties

This investigation aimed to examine the effects of a novel processing pattern, combining high hydrostatic pressure (HHP) with germination, on the embryo growth and physicochemical characteristics of wholegrain brown rice (WBR). WBR grains were firstly subjected to mild HHP stress (30–90 MPa/5 min) and then incubated at 37 °C for 52 h for obtaining germinated samples (GBR). The results showed that HHP shock resulted in a delayed embryo growth of WBR grains, maintaining acceptable sprouting rates ranging from 65% to 76% when germination was finished. The contents of gama-aminobutyric acid in GBR were greatly increased responding to HHP stress, showing pressure intensities dependent. Total digestible and resistant starch contents in samples stressed at 60/90 MPa were decreased, mainly associated with high pressure-induced amorphization as revealed by SEM imaging and FTIR, which promoted starch hydrolysis during germination. Besides, the levels of zinc and iron were influenced by HHP pretreatments due to the high pressure-mediated degradation behavior for phytic acids. The storability of HHP-stressed GBR grains was significantly enhanced through reducing free fatty acids formation and maintaining color stability during a storage testing. These results obtained from the current work demonstrated that mild HHP stress pretreatment prior to germination process could be used as a promising strategy to modulate certain physicochemical characteristics of WBR products.