High Hydrostatic Pressure Treatment Research Articles

Systematic enhancement of microbial decontamination efficiency in bone graft processing by means of high hydrostatic pressure using Escherichia coli as a model organism.

To obtain bone allografts that are safe for transplantation, several processing steps for decellularization and decontamination have to be applied. Currently available processing methods, although well-established, may interfere with the biomechanical properties of the bone. High hydrostatic pressure (HHP) is known to devitalize tissues effectively while leaving the extracellular matrix intact. However, little is known about the inactivation of the contaminating microorganisms by HHP. This study aims to investigate the ability of high-pressure decontamination and to establish a treatment protocol that is able to successfully inactivate microorganisms with the final goal to sterilize bone specimens. Using Escherichia coli (E. coli) as a model organism, HHP treatment parameters like temperature and duration, pressurization medium, and the number of treatment cycles were systematically adjusted to maximize the efficiency of inactivating logarithmic and stationary phase bacteria. Towards that we quantified colony-forming units (cfu) after treatment and investigated morphological changes via Field Emission Scanning Electron Microscopy (FESEM). Additionally, we tested the decontamination efficiency of HHP in bovine cancellous bone blocks that were contaminated with bacteria. Finally, two further model organisms were evaluated, namely Pseudomonas fluorescens as a Gram-negative microorganism and Micrococcus luteus as a Gram-positive representative. A HHP protocol, using 350 MPa, was able to sterilize a suspension of stationary phase E. coli, leading to a logarithmic reduction factor (log RF) of at least -7.99 (±0.43). The decontamination of bone blocks was less successful, indicating a protective effect of the surrounding tissue. Sterilization of 100% of the samples was achieved when a protocol optimized in terms of treatment temperature, duration, pressurization medium, and number and/or interval of cycles, respectively, was applied to bone blocks artificially contaminated with a suspension containing 104 cfu/mL. Hence, we here successfully established protocols for inactivating Gram-negative model microorganisms by HHP of up to 350 MPa, while pressure levels of 600 MPa were needed to inactivate the Gram-positive model organism. Thus, this study provides a basis for further investigations on different pathogenic bacteria that could enable the use of HHP in the decontamination of bone grafts intended for transplantation.

High hydrostatic pressure is similar to Holder pasteurization in preserving donor milk antimicrobial activity.

The microbiological safety of donor milk (DM) is commonly ensured by Holder pasteurization (HoP, 62.5 °C for 30 min) in human milk banks despite its detrimental effects on bioactive factors. We compared the antimicrobial properties of DM after Holder pasteurization treatment or High Hydrostatic Pressure processing (HHP, 350 MPa at 38 °C), a non-thermal substitute for DM sterilization. We assessed lactoferrin and lysozyme concentrations in raw, HHP- and HoP-treated pools of DM (n = 8). The impact of both treatments was evaluated on the growth of Escherichia coli and Group B Streptococcus in comparison with control media (n = 4). We also addressed the effect of storage of HHP treated DM over a 6-month period (n = 15). HHP milk demonstrated similar concentrations of lactoferrin compared with raw milk, while it was significantly decreased by HoP. Lysozyme concentrations remained stable regardless of the condition. Although a bacteriostatic effect was observed against Escherichia coli at early timepoints, a sharp bactericidal effect was observed against Group B Streptococcus. Unlike HoP, these results were significant for HHP compared to controls. Stored DM was well and safely preserved by HHP. Our study demonstrates that this alternative sterilization method shows promise for use with DM in human milk banks. Antimicrobial activity of donor milk after High Hydrostatic Pressure treatment has not been clearly evaluated. Donor milk lactoferrin is better preserved by High Hydrostatic Pressure than conventional Holder pasteurization, while lysozyme concentration is not affected by either treatment. As with Holder pasteurization, High Hydrostatic Pressure preserves donor milk bacteriostatic activity against E. coli in addition to bactericidal activity against Group B Streptococcus. Donor milk treated by High Hydrostatic Pressure can be stored safely for 6 months.

Effects of high hydrostatic pressure treatment: Identification and characterization of snakehead-muscle-protein-based angiotensin-converting-enzyme-inhibitory peptides

The main targets for antihypertensive peptides are renin and angiotensin-converting enzyme (ACE). Snakehead muscle protein (SMP)-based peptides generated as enzymatic protein hydrolysates under high hydrostatic pressure (HHP) contain a pool of peptides with potential natural ACE-inhibitory activity. The 12 peptides identified possess unique properties, including net charge (Glu and Lys) and hydrophobicity (Val and Pro). These peptides were docked into the ACE catalytic site, resembling the mode of inhibition exerted by lisinopril, an effective synthetic antihypertensive drug. In particular, the long-chain peptide identified (AIGTGKTASPQQAQE) exhibited potent ACE-inhibitory activity with an IC50 value of 0.076 μmol/L. The degree of inhibition of this peptide correlated with hydrogen bond interactions involving ACE residues Glu162, Gln281 and Lys511. These findings indicated that SMP-based peptides can be a potential natural ACE-inhibitory ingredient for the formulation of functional foods and nutraceuticals.

Inhibition of α-amylase digestion by a Lonicera caerulea berry polyphenol starch complex revealed via multi-spectroscopic and molecular dynamics analyses

Polyphenol-starch complexes exhibit synergistic and beneficial effects on both polyphenols and resistant starches. This study evaluates the inhibitory effects and mechanisms of α-amylase on a Lonicera caerulea berry polyphenol-wheat starch (LPWS) complex following high hydrostatic pressure treatments of 400 MPa for 30 min and 600 MPa for 30 min. The IC50 values for α-amylase inhibition by the complex were 3.61 ± 0.10 mg/mL and 3.42 ± 0.08 mg/mL at a 10 % (w/w) polyphenol content. This interaction was further supported by Fourier-transform infrared spectroscopy and circular dichroism, which confirmed that the alpha helix component of the secondary structure of α-amylase was reduced due to the complex. Multifluorescence spectroscopy revealed that the complex induces changes in the microenvironment of fluorophores surrounding the α-amylase active site. Molecular dynamics simulations and molecular docking revealed that the active site of amylose within the complex becomes enveloped in polyphenol clusters. This wrapping effect reduced the hydrogen bonds between amylose and α-amylase, decreasing from 16 groups to just one group. In summary, the LPWS complex represents a low-digestible carbohydrate food source, thus laying the groundwork for the research and development of functional foods aimed at postprandial hypoglycemic effects.

Investigation of the effect of high hydrostatic pressure on functional properties of pea protein isolate

The article presents the results of the influence of high hydrostatic pressure (HHP) on some functional properties of pea protein isolate. HHP was combined with different pH conditions to investigate the cumulative effect of HHP-based food processing conditions on the functional properties of pea protein isolate. Pea protein isolate solutions prepared at different pH conditions (5.0, 6.0, and 7.0) were subjected to HHP treatment at 200, 400, and 600 mPa at 18 °C for 5 min. The water resisting capacity (WRC), solubility and emulsifying properties of pea isolate samples were determined. It was found that treatment with NPP increased the VUS of pea protein isolates by 1.5 times. The greatest increase was observed in samples treated with a pressure of 400 mPa, at pH=7. An increase in solubility was found with an increase in pH from 6 to 7 when using a pressure of 400 and 600 mPa, however, for a sample of soybean isolate at pH 7 and a pressure of 200 mPa, on the contrary, a decrease in solubility was recorded. It has been shown that the effect of NPP on the emulsifying properties of pea protein depends on the processing conditions. In some cases, HPP can improve emulsifying properties, providing more stable emulsions. However, increasing exposure to high pressure up to 600 mPa leads to a decrease in emulsifying stability. The optimal parameters for using NPP for pea isolate proteins are a pH in the range of 6-7, and a pressure of 400 mPa.

Impact of high hydrostatic pressure and ultrasounds technologies in the autolytic process of Saccharomyces cerevisiae in a model wine system

Autolysis plays a crucial role as a technological tool in the ageing process of specific wines. This includes white, red and sparkling wines. During ageing on the lees, yeasts release different compounds that positively modify the composition of the wine. However, traditional autolytic methods can be time-consuming. This work evaluates the use of different ultrasound (US) and high hydrostatic pressure (HHP) treatments to expedite the autolytic process in Saccharomyces cerevisiae in a model wine system. The results suggest that treating yeast cells with US resulted in a faster release of nucleic acids, proteins, and total polysaccharides compared to HHP treatment. The environmental scanning electron microscopy (ESEM) of the treated lees demonstrated that the impact on the yeast cell surface was more pronounced after exposure to US compared to treatments involving HHP. In conclusion, under these conditions the US treatment effectively triggered autolysis in the wine yeast strain, facilitating the release of macromolecules in a model wine.

Microstructural Changes in Vanilla planifolia Beans after Using High-Hydrostatic-Pressure Treatment in the Curing Process.

During vanilla bean curing, the cell arrangement derived from the killing technique applied to start bean ripening is essential to obtain the characteristic aroma and flavor of vanilla. Hence, killing is an important step to release the enzymes and compounds required for vanillin production. In this work, high hydrostatic pressure (HHP) at 100-400 MPa for 5 min, using water at 7 °C as the pressure-transmitting medium, was applied as the killing method, and its effect on the microstructural changes in vanilla beans during different curing cycles (C0-C20) was evaluated and compared with that observed after scalding by using water at 100 °C for 8 s. Microstructural changes in the cross-sectioned beans were analyzed using a stereomicroscope (SM), confocal laser scanning microscopy (CLSM), and environmental scanning electron microscopy (ESEM). The vanilla beans were cross-sectioned and three main sectors were analyzed: the total, annular, and core. The morphometric descriptors, namely, area, Feret's diameter, and circularity, were quantified via digital image analysis (DIA), from which a shrinkage ratio was calculated. The results show that the total area in the beans presented a maximum decrease in the C16 of curing. The core area was most affected by the HHP treatment, mainly at 400 MPa, rather than scalding. CSLM observations revealed the autofluorescence of the compounds inside the beans. In conclusion, the use of microscopy techniques and DIA allowed us to determine the microstructural changes in the HHP-treated pods, which were found to be more numerous than those found in the scalded beans.

Effects of high hydrostatic pressure treatment on the structural properties of interfacial protein of rabbit myosin emulsion

High hydrostatic pressure (HHP) treatment (< 200 MPa) has been known to increase the emulsification properties of myosin. However, the relationship between interfacial elasticity and emulsion stability is complicated. Therefore, this study was focused on exploring the effects of high hydrostatic pressure on the physiochemical and structural properties of interfacial proteins within a stabilized oil-in-water (O/W) rabbit myosin emulsion. We analyzed the adsorption rate and structure of interfacial proteins pressurized under 0.1 [control], 100, 150, and 200 MPa prior to emulsion preparation. As the pressure was increased from 0.1 to 150 MPa, the adsorption rate of interfacial protein increased. HHP treatment caused myosin to unfold, which enhanced the exposure of reactive sulfhydryl and hydrophobic groups. Furthermore, the frequency of hydrogen bonding and hydrophobic interactions increased. As hydrogen bonding increased, the secondary structure of myosin became more stable. As the pressure increased to 200 MPa, the interfacial myosin aggregated, displaying a decreased surface hydrophobicity and reactive sulfhydryl groups (P < 0.05) and thus the emulsion stability decreased. In conclusion, HHP treatment of myosin at 150 MPa significantly improved the stability of the myosin emulsion. Industrial relevanceMyosin is an important protein in meat and its emulsion stability can be enhanced by HHP. This study reveals the conformational mechanism by which HHP improves the stability of myosin emulsions, providing potential theoretical basis for the application of HHP treatment to improve the quality of emulsified meat products as a non-thermal processing technology in the practical production.

Evaluation of Integrity of Allogeneic Bone Processed with High Hydrostatic Pressure: A Pilot Animal Study.

Processing of bone allografts with strong acids and γ-sterilization results in decreased biomechanical properties and reduction in osteogenecity and osteoconductivity. High hydrostatic pressure (HHP) treatment could be a gentle alternative to processing techniques usually applied. HHP is known to induce devitalization of cancellous bone while preserving biomechanical stability and molecules that induce cell differentiation. Here, a specific HHP protocol for devitalization of cancellous bone was applied to rabbit femoral bone. Allogeneic bone cylinders were subsequently implanted into a defect in the lateral condyles of rabbit femora and were compared to autologous bone grafts. Analysis of bone integration 4 and 12 weeks postoperatively revealed no differences between autografts and HHP-treated allografts regarding the expression of genes characteristic for bone remodeling, showing expression niveous comparable to original bone cylinder. Furthermore, biomechanical properties were evaluated 12 weeks postoperatively. Autografts and HHP-treated allografts both showed a yield strength ranging between 2 and 2.5 MPa and an average bone mass density of 250 mg/cm2. Furthermore, histological analysis of the region of interest revealed a rate of 5 to 10% BPM-2 and approximately 40% osteocalcin-positive staining, with no marked differences between allografts and autografts demonstrating comparable matrix deposition in the graft region. A suitable graft integrity was pointed out by μCT imaging in both groups, supporting the biomechanical data. In summary, the integrity of HHP-treated cancellous bone allografts showed similar results to untreated autografts. Hence, HHP treatment may represent a gentle and effective alternative to existing processing techniques for bone allografts.

The effect of high hydrostatic pressure on the structure of whey proteins-guar gum mixture

The effect of high hydrostatic pressure (HHP) on the structural properties of whey protein concentrate (WPC) and guar gum mixture has been investigated at pH 5. WPC (6 % w/v) and guar gum (0.25 % w/v) mixture was freeze dried after adjusting pH and treated at different pressure levels (0–600 MPa) for 0–30 min. The solubility of treated powders decreased significantly (p < 0.05) as treatment time and pressure levels increased. Thermal analysis showed an increase in denaturation temperature after HHP treatment at 600 MPa. A more crystalline structure was observed in samples treated with 600 MPa for 20 and 30 min. With increasing pressure and time, particle size of the samples increased and the highest particle size was belonged to sample treated at 600 MPa for 30 min (759.66 nm). SEM results exhibited that by applying the pressure, irregularity of shapes and particle size increased while the apparent cracks decreased. FTIR results indicated that HHP treatment changed shift in bond and peak intensity. As reported in the current study, the application of HHP treatment as a green physical technology on protein-polysaccharide mixture could be used to improve interaction of protein and polysaccharide.

Antirotaviral activity of dairy byproducts enriched in fractions from hyperimmune bovine colostrum: the effect of thermal and high hydrostatic pressure treatments.

Nowadays, rotaviruses remain a major health burden, especially in developing countries, and strategies complementary to vaccination are needed. In this view, dairy fractions have attracted great scientific interest, due to their high content of bioactive compounds. The objective of this study was to evaluate the antiviral activity of whey and buttermilk enriched in proteins from hyperimmune bovine colostrum (HBC) against rotavirus. The enriched fractions were spray-dried and subsequently tested for their neutralizing activity against the bovine rotavirus WC3 strain in vitro, using differentiated Caco-2/TC7 cells. The highest antirotaviral activity was observed when whey and buttermilk were enriched in purified immunoglobulin G (IgG), showing complete rotavirus neutralization at concentrations of 3 and 6 mg mL-1 for whey and buttermilk, respectively. Additionally, the use of a crude immunoglobulin fraction also gave satisfactory results. The inhibitory activities of all samples significantly decreased after the application of heat, except for the IgG-enriched buttermilk which showed a slight increase of activity following the application of short-time treatments (75 or 85 °C for 20 s). This sample also showed a significant increase of activity (13%) after the application of low-intensity high hydrostatic pressure treatment (400 MPa for 5 min). The maximum loss of bioactivity was observed at 600 MPa for 10 min (31 and 20% for whey- and buttermilk-based formulas, respectively). This study provides relevant information on the potential of whey, buttermilk, and HBC to be part of functional products as complementary strategies to combat rotavirus infections.

Influence of high hydrostatic pressure treatment on cassava flour's volatile retention performance

The granular alterations and microstructural disruption associated with high hydrostatic pressure-induced gelatinisation of starches in cassava flour reduced its ability to bind volatiles but it remained stable during storage.

The Application of High-Hydrostatic-Pressure Processing to Improve the Quality of Baked Products: A Review.

The current trend in the food industry is towards "clean label" products with high sensory and nutritional quality. However, the inclusion of nutrient-rich ingredients in recipes often leads to sensory deficiencies in baked goods. To meet these requirements, physically modified flours are receiving more and more attention from bakery product developers. There are various findings in the literature on high hydrostatic pressure (HHP) technology, which can be used to modify various matrices so that they can be used as ingredients in the baking industry. HHP treatments can change the functionality of starches and proteins due to cold gelatinization and protein unfolding. As a result, the resulting ingredients are more suitable for nutrient-rich bakery formulations. This review describes the information available in the literature on HHP treatment conditions for ingredients used in the production of bakery products and analyses the changes in the techno-functional properties of these matrices, in particular their ability to act as structuring agents. The impact of HHP-treated ingredients on the quality of dough and bakery products and the effects on some nutritional properties of the treated matrices have been also analysed. The findings presented in this paper could be of particular interest to the bakery industry as they could be very useful in promoting the industrial application of HHP technology.

Application of White-Wine-Pomace-Derived Ingredients in Extending Storage Stability of Fresh Pork Burgers.

White wine pomace, a by-product from winemaking, was stabilized after the application of thermal blanching (with the aim of deactivating the polyphenoloxidase enzyme), milling, and processing by hydrostatic high-pressure treatment (with the aim of reducing initial microbial loads while preserving phenolic compounds content). The valorized pomace (VP) ingredient was added at different proportions to pork burgers (0.5%, 1%, and 3% w/w) to improve their preservation, and the effect was compared to those produced by sulfites and with a control (without sulfites or VP). Burgers were vacuum-packed and refrigerated for 7 days. Microbiological, color, oxidation, and sensory parameters were analyzed. Neither sulfites nor VP reduced the microbial development of most microorganism groups evaluated (p > 0.05); however, both prevented coliform growth during storage (p < 0.01). The use of sulfites prevented the discoloration of burgers during storage, while VP had no effect (p < 0.001). On the contrary, VP limited lipid and protein oxidation development during storage (p > 0.05), while sulfites had no effect. Therefore, the use of VP from white wine production could have an antioxidant effect but a limited antimicrobial or color-protective effect for the preservation of pork burgers.

Effect of alternative pre-treatments and fermentation on quality characteristics of oyster mushrooms

AbstractBesides their unique taste and texture, mushrooms are a promising source of important nutrients, including dietary fiber, amino acids, minerals, and vitamins. Fresh mushrooms, however, can only endure for a brief time, typically up to three days at ambient conditions. Different methods have been used to preserve mushrooms for a prolonged period, such as drying, cooking, frying, irradiation and fermentation. The objective of the current study is to investigate the effect of different pre-treatments and fermentation on physicochemical, textural, and microbial properties of oyster mushrooms. The fresh oyster mushroom was considered as control and 6 alternative pre-treatment methods were used as; blanching in water, steaming, oven cooking, microwave, High Hydrostatic Pressure and UV Light treatment. Moisture, pH, yield, color, texture, and microbiological analyses were performed on each pre-treatment group before and after fermentation. Our results showed that the quality attributes of oyster mushrooms were significantly affected by the usage of different pre-treatments.

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.

Effect of high hydrostatic pressure on aroma volatile compounds and aroma precursors of Hami melon juice.

High hydrostatic pressure (HHP) treatment is an effective technique for processing heat-sensitive fruits and causes changes in volatile compounds and their precursors while maintaining quality. We investigated the changes and correlations of volatile compounds, related enzyme activities and precursor amino acids, and fatty acids in Hami melon juice under 350-500 MPa pressure. The application of HHP treatment resulted in a considerable reduction of esters and a substantial increase in aldehydes and alcohols in C6 and C9. Activities of lipoxygenase (LOX), alcohol acyltransferase (AAT), and phospholipase A2 (PLA2) were lower than those of the untreated group, alcohol dehydrogenase (ADH) activity was reversed. When compared to fresh cantaloupe juice, there was an increase in both the types and contents of amino acids with lower total fatty acid contents than the control group. Positive correlations were observed among six ester-related substances and eight alcohol-related substances. Additionally, the correlations between volatile compounds and fatty acids were more substantial compared to those between volatile compounds and amino acids. HHP treatment increases Hami melon flavor precursors and is an effective way to maintain the aroma volatile compounds and flavor of Hami melon juice.

Effects of high hydrostatic pressure on peelability and quality of Crayfish (Procambarus clarkii).

Peeling of crayfish is a very important process in production. Crayfish peeling by machine can increase production efficiency and enhance the safety in production process. The tight muscle-shell attachment causes difficulty in peeling freshly caught crayfish. However, few studies have explored the changes in crayfish quality under favourable shell-loosening treatments. In this study, the shell-loosening properties of crayfish and changes in crayfish quality, microstructure, and protein fluorescent features were investigated after high hydrostatic pressure treatment (HHP). New methods were established to measure the peeling performance of crayfish, which are peelabibity and meat yelid rate (MYR). The normalization of peelability and MYR were verified by different weights of crayfish tails and different treatments. The peeling effect of HHP-treated crayfish was evaluated by a new quantitative measurement method, and meat yield rate (MYR) was calculated. The results showed that all the HHP treatments reduced crayfish peeling work and increased MYR. The HHP treatment provided better crayfish quality in terms of texture and color and enlarged the shell-loosening gap. Among all HHP treatments, 200 MPa treatment exhibited a lower peeling work , higher MYR, and an expansion of the shell-loosening gap reaching up to 573.8 um. At the same time, 200MPa treatment can maintain the quality of the crayfish. The findings outlined above suggest that high pressure is a promising method used to loosen crayfish shells. 200 MPa is an optimal HHP treatment condition for crayfish peeling, exhibiting a promising application in industrial processing. This article is protected by copyright. All rights reserved.

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.

Effect of Single and Two-Cycles of High Hydrostatic Pressure Treatment on the Safety and Quality of Chicken Burgers.

The aim of this study was to evaluate the effect of two cycles of high hydrostatic pressure (HHP) treatment on chicken burgers after storage at refrigeration (4 °C) for 15 days, in comparison with the application of a single cycle of high hydrostatic pressure treatment, as well as compared with non-treated burgers. Samples were treated at 400 and 600 MPa and a single or two cycles were applied. The results showed that mesophilic, psychrotrophic molds, yeast, and coliforms were significantly reduced by HHP treatment (p < 0.05), 600 MPa/1 s (2 cycles) leading to the maximum inactivation. Concerning color parameters, a significant increase in lightness/paleness (L*) and a reduction in redness (a*) and yellowness (b*) (p < 0.05) was observed in samples as 600 MPa were applied. Moreover, 600 MPa/1 s (2 cycles) caused the highest differences in the meat color (ΔE processing) of the chicken burgers. No HHP treatment significantly affected the degree of oxidation of samples (p > 0.05). However, 600 MPa/1 s (2 cycles) samples showed the highest values of TBA RS content after 15 days of storage (p < 0.05). Finally, the appearance, odor, taste, and global perception of cooked burgers were similar in all groups (p < 0.05). Therefore, treatments at 600 MPa produced a significant reduction in microbial counts but modified the color; however, the discoloration effect in the cooked burgers was not noticed by panelists.