Application Of High Hydrostatic Pressure Research Articles

Changes in the microbiota and colour of pork meat batter during refrigerated storage in relation to the application of High Hydrostatic Pressure

The aim of this work was to study the effect of High Hydrostatic Pressures (HHP) on microbial degradation pattern and colour stability of pork meat batters used to produce fresh sausages. Besides treatments at 300 or 600 MPa for 5 min, pH (5.8 vs 5.4) and nitrite addition (100 vs. 0 mg/kg) were considered as variables. A not treated control was also monitored. The different samples were stored at 4°C and periodically analysed for their microbiota and colour. At the end of shelf life (TMC > 6.5 log CFU/g) a metagenomic analysis was also carried out to better clarify the effect of the treatments on microbial spoilage patterns. The results showed that the treatment at 300 MPa slightly affected initial cell load, but slowdown growth kinetics, especially at low pH, while 600 MPa strongly reduced microbial spoilage. The application of HHP was able to prolong shelf life of meat batters, from about two weeks (control) to 40 and 80 days in the case of treatments at 300 and 600 MPa, respectively. Metagenomic analysis revealed different degradation patterns in relation to tested variables: untreated samples showed the prevalence of Brochothrix spp., while the application of HHP determined the presence also of Carnobacterium, Bacillus, and Staphylococcus, depending on the treatment and the meat batter pH. Concerning colour, differences were mainly observed in redness (a*) and were due to the presence of nitrite. These findings suggest that HHP can be a feasible strategy to stabilize fresh sausages, although further studies are needed to assess their safety.

Application of high-hydrostatic pressure to extend shelf life of miso-marinated Escolar loins during cold storage

The changes in the microbiological and chemical qualities of escolar meat following high-pressure processing (HPP) (300–600 MPa, 5 min) along with miso marinade for 15 days with refrigeration were evaluated. Miso marinade and HPP treatment of escolar meat had synergistic inactivating effects on microorganisms that were more pronounced at higher pressures. In addition, when stored at 4°C, the combination of miso marinade and HPP treatment significantly delayed microbial growth and total volatile basic nitrogen (TVBN) production and inhibited pH changes. Using TVBN < 25 mg/100 g as the criterion for freshness, miso marinade and HPP treatment (300–600 MPa) extended the refrigerated storage period from 3 days without treatment and 6 days with miso marinade alone to 15 days. In addition, high-throughput sequencing analysis showed that the combination of miso marinade and HPP treatment significantly altered the microbiome of the fish during refrigeration, thereby slowing the spoilage process. This study demonstrated that miso marinade along with HPP treatment can improve color and texture, inhibit microbial growth, delay quality deterioration, and prolong the shelf life of fish meat. Therefore, high pressure together with miso marinade is an effective hurdle technique for improving the quality and freshness of aquatic products.

High hydrostatic pressure treatment for advanced tissue grafts in reconstructive head and neck surgery.

The increasing importance of regenerative medicine has resulted in a growing need for advanced tissue replacement materials in head and neck surgery. Allo- and xenogenic graft processing is often time-consuming and can deteriorate the extracellular matrix (ECM). High hydrostatic pressure (HHP)-treatment could allow specific devitalization while retaining the essential properties of the ECM. Porcine connective tissue and cartilage were HHP-treated at 100-400 MPa for 10 min. Structural modifications following HHP-exposure were examined using electron microscopy, while devitalization was assessed through metabolism and cell death analyses. Furthermore, ECM alterations and decellularization were evaluated by histology, biomechanical testing, and DNA content analysis. Additionally, the inflammatory potential of HHP-treated tissue was evaluated in vivo using a dorsal skinfold chamber in a mouse model. The devitalization effects of HHP were dose-dependent, with a threshold identified at 200 MPa for fibroblasts and chondrocytes. At this pressure level, HHP induced structural alterations in cells, with a shift toward late-stage apoptosis. HHP-treatment preserved ECM structure and biomechanical properties, but did not remove cell debris from the tissue. This study observed a pressure-dependent increase of markers suggesting the occurrence of immunogenic cell death. In vivo investigations revealed an absence of inflammatory responses to HHP-treated tissue, indicating a favorable biological response to HHP. In conclusion, application of HHP devitalizes fibroblasts and chondrocytes at 200 MPa while retaining the essential properties of the ECM. Prospectively, HHP may simplify the preparation of allo- and xenogenic tissue replacement materials and increase the availability of grafts in head and neck surgery.

Integrated metabolomics analysis of chill-stored rose shrimp (Parapenaeus longirostris) treated with different pressure levels of high hydrostatic pressure by 1H-NMR spectroscopy.

The antimicrobial effects of high hydrostatic pressure (HHP) treatments on chill-stored seafood are well-documented, while their impact on the metabolic profile of seafood, especially the metabolome of fish flesh, and remains underexplored. Addressing this gap, this study investigates the effects of HHP on the metabolome of chill-stored rose shrimp by conducting multivariate data analysis based on untargeted proton nuclear magnetic resonance observations. Vacuum-packed rose shrimp samples were subjected to HHP at 0, 400, 500, and 600MPa for 10 min and then stored at 2-4°C. The microorganism analysis and metabolic analysis were carried out on days 1 and 14. HHP treatment effectively deactivated Lactobacillus spp., Escherichia coli, Pseudomonas spp., total Coliforms, and sulfite-reducing anaerobic bacteria. Consequently, HHP treatment significantly reduced the formation rate of decay-related metabolites, such as hypoxanthine, trimethylamine, and biogenic amines, which exhibited significant accumulation in untreated samples. Multivariate unsupervised analyses provided insights into the overall changes in the metabolite profile induced by HHP. Metabolic pathway analysis revealed several pathways underlying spoilage, including pyruvate metabolism, valine, leucine, and isoleucine biosynthesis, purine metabolism, methane metabolism, glycine, serine, and threonine metabolism, citrate cycle (TCA cycle), glycolysis/gluconeogenesis, alanine, aspartate, and glutamate metabolism, sulfur metabolism, pantothenate and CoA biosynthesis, glutathione metabolism, and glyoxylate and dicarboxylate metabolism. Importantly, these pathways underwent alterations due to the application of HHP, particularly at high-pressure levels. In summary, the results unveil the potential mechanisms of HHP effects on chill-stored rose shrimps.

The Influence of High Hydrostatic Pressure on Selected Quality Features of Cold-Storage Pork Semimembranosus Muscle.

The primary objective of this investigation was to assess the influence of high hydrostatic pressure (HHP) and the duration of cold storage on the physicochemical, technological, and sensory attributes as well as the nutritional composition and shelf life of meat. The experimental framework involved utilizing samples derived from the semimembranosus muscle of pork. Each muscle obtained from the same carcass was segmented into six distinct parts, with three designated as control specimens (K) and the remaining subjected to vacuum packaging and subsequent exposure to high hydrostatic pressure (200 MPa at 20 °C for 30 min). Comprehensive laboratory analyses of the meat were conducted at 1, 7, and 10 days post slaughter. The meat was cold-stored at +3 ± 0.5 °C. The findings of the study elucidated that the application of high hydrostatic pressure exhibited a favorable impact on the extension of the raw meat's shelf life. The tests showed a significant (p < 0.05) decrease in the total number of microorganisms compared to the control sample after 7 (K: 4.09 × 105, HHP: 2.88 × 105 CFU/g) and 10 (K: 7.40 × 105, HHP: 2.42 × 105 CFU/g) days of cold storage. It was also found that using HHP increased the pH value after 1 (K: 5.54, HHP: 5.77) and 7 (K: 5.60, HHP: 5.87) days of storage.

Evaluation of dual modification by high hydrostatic pressure and annealing on the physicochemical properties of bean starch

This study investigated the physical modifications by high hydrostatic pressure (HHP) at 600 MPa for 30 min/30 °C, annealing (AN) at 50 °C/24 h and the combination of both (HHP + AN and AN + HHP) applied to yellow bean starch to verify changes in morphology, X-ray diffraction, molecular order, thermal properties and pasting properties of native (NS) and modified starches. Morphological analysis showed loss of sphericity and increase in diameter with the appearance of pores on the surface after application of treatments. The AN starch showed lower values of syneresis, degree of double helix (DD), order (DO), and viscosity of the paste obtained by RVA. It exhibited a Vh-type classification with the appearance of the amylose–lipid complex. However, the gelatinization temperatures, as well as the enthalpy of gelatinization, were significantly higher. On the other hand, the starch treated with HHP showed a higher Setback (SB) value. The greatest modifications were found for the starches subjected to the combined treatments (AN + HHP) and (HHP + AN), where the order of the treatments was significant for the morpho-structural changes of yellow bean starch. According to the micrographs, the surface aspect was altered, with AN + HHP showing greater irregularities and flat yet irregular faces, as well as a larger granule diameter (147.05). The X-ray diffractogram showed a reduction in crystallinity from 28.14 % (NS) to 18.09 % (AN + HHP) and classified the starch as type “A”. The double modification (HHP + AN and AN + HHP) reduced the gelatinization temperature and the enthalpy of gelatinization but had no effect on the bands of the FT-IR spectrum. There was only a reduction in the degree of order and the double helix. Finally, the treatment with AN + HHP is more effective as the gelatinization with AN facilitates the application of HHP. Both methods used are classified as physical (thermal and non-thermal), aiming to minimize environmental impacts and achieve faster and safer morpho-structural modification without leaving chemical residues in the products.

Effects of high pressure synergistic enzymatic physical state and concentration on the denaturation of polyphenol oxidase.

The synergistic effect of the initial state of the enzyme and pressure level on the denaturation of PPO has not been clear yet, but it significantly affects the application of high hydrostatic pressure (HHP) in the enzyme-containing food processing. Solid (S-) and low/high concentration liquid (LL-/HL-) polyphenol oxidase (PPO) was used as the study object, and the microscopic conformation, molecular morphology and macroscopic activity of PPO under HHP treatments (100-400MPa, 25°C/30min) were investigated by spectroscopic techniques. The results show that the initial state has a significant effect on the activity, structure, active force and substrate channel of PPO under pressure. The effec can be ranked as follows: physical state>concentration>pressure, S-PPO>LL-PPO>HL-PPO. High concentration has a weakening effect on the pressure denaturation of the PPO solution. Under high pressure, the α-helix and concentration factors play a crucial role in stabilizing the structure.

Release of anthocyanins encapsulated by high hydrostatic pressure-treated micellar casein: Effect of serum Ca2+ level during in vitro digestion

Anthocyanins (ACNs) possess the natural advantage of gastric stabilization and has the potential to be adopted for the delivery system design for prolonged gastric release to enhance its bioavailability. In this study, micellar casein treated with high hydrostatic pressure (100, 300, and 500 MPa) was applied to load ACNs, and exogenous serum Ca2+ (0.15, 2, and 5 mM) controlled the gastric aggregation behavior of casein during in vitro digestion. The results showed that the high level of pressure dissociated the micellar structure and provided more cross-linking possibilities for serum Ca2+. Furthermore, the high serum Ca2+ level enhanced gastric aggregation of casein subunits and submicelles leading to delayed gastric emptying, and controlled the slow release of ACNs, which contributed to prolong the ACN retention in the stomach. Industrial relevanceThe application of high hydrostatic pressure (HHP) in food sterilization has been relatively mature, and there is an urgent need to expand it toward the nutritional and health field in search of high added value. Herein, HHP was applied to solve the problem of low bioavailability of ACNs based on the ingenious relationship between HHP and casein micelles. The research data can help to develop nutraceuticals or high satiety foods with ACNs as the main functional component at low cost.

Preservation of white wine pomace by high hydrostatic pressure

The effect of different high hydrostatic pressure (HHP) treatments (400, 600 MPa for 1, 6 min) on white wine pomace was studied throughout storage conditions (270 days) at different temperature conditions (4° and 20 °C). The final use of this product would be as an ingredient for food products preservation. Microbiological, enzyme and physico-chemical parameters were evaluated after processing and during storage. HHP greatly reduced the microbial counts of treated pomace and allowed obtaining a safe product with a long shelf-life at 4 and 20 °C. The HHP treatment also preserved phenolic compounds content, however an important reduction of these compounds was found during storage since the polyphenol oxidase enzyme remained active after the treatment and during storage. Phenolic compounds were better preserved during storage at 4 °C than at 20 °C. The application of HHP at 600 MPa/6 min and the refrigeration of the treated pomace would allow obtaining a microbiologically safe pomace with high levels of phenolic compounds with a shelf-life of 90 days. The activity of the enzyme should be limited in future to ensure a long shelf-life of the processed pomace.

Preserving Raw Oysters with High Hydrostatic Pressure and Irradiation Technology

Refrigerated raw oysters, including Pacific oysters (Magallana gigas), eastern oysters (Crassostrea virginica), and European flat oysters (Ostrea edulis), are popular seafood products. Pathogenic contamination and spoilage during storage and transport limit their shelf life. High hydrostatic pressure (HHP) and irradiation effectively reduce pathogens and spoilage microorganisms in raw oysters while preserving their taste and texture. This review article presents a comprehensive analysis of the use of HHP and irradiation as sanitation methods for raw oysters, incorporating findings from geographical distribution, mathematical modeling, and radiation quality’s impact on sterilization efficacy. The results demonstrate that untreated eastern oysters can maintain a total bacterial count below the recommended limit of 107 CFU/g for only 2–3 weeks at 5 °C, and are at risk of harboring pathogens such as Vibrio spp. and norovirus. HHP treatment at 600 MPa and irradiation treatment at 2 kGy can effectively reduce the pathogen load in raw oysters. However, supplementary measures such as additional cleaning or lower temperatures are required to prolong the shelf life of treated raw oysters to 2–3 weeks. Taken together, the application of HHP and irradiation to raw oyster sanitation represents a promising approach for enhancing the safety and quality of this beloved seafood delicacy.

Effects of high hydrostatic pressure on antimicrobial protein stability and the rheological and shelf-life properties of donkey milk.

The effects of high hydrostatic pressure (HHP) and heat treatments on antimicrobial protein stability and on the physico-chemical, microbiological, rheological and shelf-life properties of donkey milk were investigated. Although heat treatment at 75°C for 2 min resulted in 1.50 log CFU ml-1 microbial inactivation, losses in activities of lysozyme (58%) and lactoferrin (82%) were observed due to whey protein denaturation. By contrast, HHP application at 400 MPa caused lower enzyme activity losses (22 and 37% respectively) whilst maintaining a significant reduction of microbial load (1.80 log CFU ml-1). Color analyses showed that the lightness values of all samples decreased during storage. Higher flow consistency (viscosity) and lower flow behavior indexes were observed in heat-treated samples compared to untreated and HHP-treated ones, which can be explained by advanced protein denaturation during heat-treatment. The results suggest that HHP is a more suitable process than heat treatment for preservation of donkey milk within the conditions studied.

Using pressure to unravel the structure–dynamic-disorder relationship in metal halide perovskites

The exceptional optoelectronic properties of metal halide perovskites (MHPs) are presumed to arise, at least in part, from the peculiar interplay between the inorganic metal-halide sublattice and the atomic or molecular cations enclosed in the cage voids. The latter can exhibit a roto-translative dynamics, which is shown here to be at the origin of the structural behavior of MHPs as a function of temperature, pressure and composition. The application of high hydrostatic pressure allows for unraveling the nature of the interaction between both sublattices, characterized by the simultaneous action of hydrogen bonding and steric hindrance. In particular, we find that under the conditions of unleashed cation dynamics, the key factor that determines the structural stability of MHPs is the repulsive steric interaction rather than hydrogen bonding. Taking as example the results from pressure and temperature-dependent photoluminescence and Raman experiments on MAPbBr_3 but also considering the pertinent MHP literature, we provide a general picture about the relationship between the crystal structure and the presence or absence of cationic dynamic disorder. The reason for the structural sequences observed in MHPs with increasing temperature, pressure, A-site cation size or decreasing halide ionic radius is found principally in the strengthening of the dynamic steric interaction with the increase of the dynamic disorder. In this way, we have deepened our fundamental understanding of MHPs; knowledge that could be coined to improve performance in future optoelectronic devices based on this promising class of semiconductors.

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.

Potential Application of High Hydrostatic Pressure on the Production of Hydrolyzed Proteins with Antioxidant and Antihypertensive Properties and Low Allergenicity: A Review.

The high hydrostatic pressure (HHP) process has been studied for several applications in food technology and has been commercially implemented in several countries, mainly for non-thermal pasteurization and shelf-life extension of food products. HHP processing has been demonstrated to accelerate proteolytic hydrolysis at a specific combination of pressure and pressure-holding time for a given protein source and enzyme. The enzymatic hydrolysis of proteins is a well-known alternative to producing biologically active peptides, with antioxidant and antihypertensive capacity, from different food protein sources. However, some of these protein sources contain allergenic epitopes which are often not degraded by traditional hydrolysis. Moreover, the peptide profile and related biological activity of a hydrolysate depend on the protein source, the enzymes used, the parameters of the proteolysis process (pH, temperature, time of hydrolysis), and the use of other technologies such as HHP. The present review aims to provide an update on the use of HHP for improving enzymatic hydrolysis, with a particular focus on studies which evaluated hydrolysate antihypertensive and antioxidant capacity, as well as residual allergenicity. Overall, HHP has been shown to improve the biological properties of hydrolysates. While protein allergenicity can be reduced with traditional hydrolysis, HHP can further reduce the allergenicity. Compared with traditional hydrolysis methods, HHP-assisted protein hydrolysis offers a greater opportunity to add value to protein-rich products through conversion into high-end hydrolysate products with enhanced nutritional and functional properties.

A study on the structural, physicochemical, rheological and thermal properties of high hydrostatic pressurized pearl millet starch

Starch in native form has limited application due to functional and physicochemical characteristics. To overcome these limitations, starch can be modified by non-thermal technologies such as high hydrostatic pressure (HHP). This study investigates high-pressure-induced gelatinization and the effect of this process on the structural, functional, morphological, pasting, thermal, physical and rheological properties of millet starch. The suspension of millet starch and water was pressurized at 200, 400 and 600 MPa for 10, 20 and 30 min to modify the starch in terms of structure, morphology, some physicochemical and rheological properties. Swelling strength and starch solubility decreased as a result of treatment with HHP. All treatments caused to increase in water holding capacity of the starch (from 0.66 % for native starch to 2.19 % for 600 MPa-30 min). Thermal analysis showed a decrease in gelatinization temperature and enthalpy of gelatinization and the pasting properties showed a decrease in the peak viscosity after HHP treatment. In addition, HHP treatment caused to increase in the hydration ability of starch by creating porosity and gaps in the granule surface and increasing the specific surface area. HHP application resulted in an increase in the peak time and pasting temperature and a decrease in breakdown and peak viscosities, final viscosity and setback viscosity in comparison with native starch of millet. The starch sample treated with 600 MPa for 30 min had the lowest syneresis and retrogradation ability. Increasing pressure and the time led to an increase in the elastic nature of the starch samples. According to the results, it is possible to increase usage area of starches in the food industry by improving its technological with HHP. This green physical technology can influence the quality parameters of starch, which can provide benefits for product machining and economic purposes.

High hydrostatic pressure assisted by food-grade enzymes as a sustainable approach for the development of an antioxidant ingredient

Apple is one of the most important fruits in the world. The elaboration of apple-based products such as cider or apple juice generates around 3–4.2 million tonnes of apple by-product that are annually discarded. Apple by-product has been described as an interesting source of bioactive compounds, including polyphenols. These valuable components, once extracted, could enable the usage of the apple by-product as a natural antioxidant ingredient. The aim of the present work was to address the effect of high hydrostatic pressure (HHP), and HHP assisted by two alternative food-grade enzymes, Celluclast®, and Ultraflo®. For that purpose, the total phenolic content was measured by Folin-Ciocalteu and Fast-Blue BB assays. Furthermore, antioxidant capacity was determined by three analytical methods (DPPH, ORAC and FRAP) and the characterization of phenolic compounds was carried out by Chromatography and Mass Spectrometry analysis. Results indicated a significant increase of the total phenolic content and the antioxidant capacity after the HHP aided by Celluclast® or Ultraflo® treatment. Conversely, the exclusive application of HHP induced minor changes. Thus, the combination of HHP and the food-grade enzymes Celluclast® or Ultraflo®, has proved to be an effective strategy for the extraction of natural antioxidant compounds from the apple by-product.

Integrative Physiological and Transcriptome Analysis Reveals the Mechanism for the Repair of Sub-Lethally Injured Escherichia coli O157:H7 Induced by High Hydrostatic Pressure

The application of high hydrostatic pressure (HHP) technology in the food industry has generated potential safety hazards due to sub-lethally injured (SI) pathogenic bacteria in food products. To address these problems, this study explored the repair mechanisms of HHP-induced SI Escherichia coli O157:H7. First, the repair state of SI E. coli O157:H7 (400 MPa for 5 min) was identified, which was cultured for 2 h (37 °C) in a tryptose soya broth culture medium. We found that the intracellular protein content, adenosine triphosphate (ATP) content, and enzyme activities (superoxide dismutase, catalase, and ATPase) increased, and the morphology was repaired. The transcriptome was analyzed to investigate the molecular mechanisms of SI repair. Using cluster analysis, we identified 437 genes enriched in profile 1 (first down-regulated and then tending to be stable) and 731 genes in profile 2 (up-regulated after an initial down-regulation). KEGG analysis revealed that genes involved in cell membrane biosynthesis, oxidative phosphorylation, ribosome, and aminoacyl-tRNA biosynthesis pathways were enriched in profile 2, whereas cell-wall biosynthesis was enriched in profile 1. These findings provide insights into the repair process of SI E. coli O157:H7 induced by HHP.

Application of High Hydrostatic Pressure in fresh purple smoothie: Microbial inactivation kinetic modelling and qualitative studies.

The inactivation kinetics of Listeria monocytogenes during High Hydrostatic Pressure (HHP) treatments was studied in a purple smoothie based of fresh fruit and vegetables. Pressure intensity studied was 300, 350, 400 and 450 MPa. Untreated samples were used as control. Furthermore, the effects on quality attributes (sensory, total soluble solids content, colour, titratable acidity, pH, vitamin C and total phenolics content) were also monitored. Microbial inactivation was modelled as a function of the HHP intensity using the Geeraerd model. Shoulder and tail effects were observed only for the 300 MPa pressure assayed, supporting a multiple hit kinetic inactivation of critical factors. Increasing the HHP intensity resulted in a faster inactivation with tailing. A strong positive correlation was observed between the pressure level and the inactivation rate (k). Hence, a linear model was used to describe the relationship between both variables. Nevertheless, further data are required to confirm this secondary model. Quality was mostly unaffected by the HHP treatments, except for the vitamin C content, which reported reductions of 26 and 21% after 300 and 350 MPa, respectively. In conclusion, HHP can be a viable technology for processing fruit and vegetable-based smoothies to preserve quality and safety. A pressure of 400 MPa is advisable to ensure an efficient microbial inactivation with the best sensory and nutritional quality retention.

High Hydrostatic Pressure to Increase the Biosynthesis and Extraction of Phenolic Compounds in Food: A Review.

Phenolic compounds from fruits and vegetables have shown antioxidant, anticancer, anti-inflammatory, among other beneficial properties for human health. All these benefits have motivated multiple studies about preserving, extracting, and even increasing the concentration of these compounds in foods. A diverse group of vegetable products treated with High Hydrostatic Pressure (HHP) at different pressure and time have shown higher phenolic content than their untreated counterparts. The increments have been associated with an improvement in their extraction from cellular tissues and even with the activation of the biosynthetic pathway for their production. The application of HHP from 500 to 600 MPa, has been shown to cause cell wall disruption facilitating the release of phenolic compounds from cell compartments. HPP treatments ranging from 15 to 100 MPa during 10–20 min at room temperature have produced changes in phenolic biosynthesis with increments up to 155%. This review analyzes the use of HHP as a method to increase the phenolic content in vegetable systems. Phenolic content changes are associated with either an immediate stress response, with a consequent improvement in their extraction from cellular tissues, or a late stress response that activates the biosynthetic pathways of phenolics in plants.

Application of high hydrostatic pressure (HHP) shock to induce triploid development in the European grayling (Thymallus thymallus L.)

Use of parental individuals from allochthonous lineages to produce stocking specimens resulted in genetic contamination of many local European grayling (Thymallus thymallus) populations. Stocking programs including triploid individuals that are not able to reproduce with stocks located in natural habitats due to being reproductively sterile could contribute to populations of the European grayling and prevent regional lineages from the genetic pollution. The main goal of the present research, therefore, was to provide conditions for triploidization of the European grayling and examine gonads of triploid individuals. High Hydrostatic Pressure (HHP) shock (9000 psi/5 min.) applied to activated and incubated grayling eggs at 10 °C between the 17 min. 30 sec. and 20 minute timepoints subsequent to the time of insemination resulted in inhibition of the second polar body release and triploidization. Histological analysis confirmed that all 1-yr-old cytogenetically confirmed triploids had gonadal tissues indicative of sterility with the gonads being composed of connective tissue including fibroblasts, adipocytes and degenerated epithelial structures without there being any differentiated germ cells detected. There were no differences in the body length and Fulton’s condition factor between 1 year old diploid and triploid grayling, however, the average body weight was markedly less in triploid than diploid specimens. Although, 1-yr-old triploid European female and male graylings did not have fully developed gonads, before these triploid specimens are deemed safe, as a result of being reproductively sterile for stocking in natural grayling habitats, there needs to be further examination of the 2- and 3-year-old triploid specimens.