Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.     

Food processing by high hydrostatic pressure

The use of high hydrostatic pressures (HHP) for food processing is finding increased application within the food industry. One of the advantages of this technology is that because it does not use heat, sensory, and nutritional attributes of the product remain virtually unaffected, thus yielding products with better quality than those processed traditional methods. HHP have the ability to inactivate microorganisms as well as enzymes responsible for shortening the life of a product. In addition to lengthening the shelf-life of food products, HHP can modify functional properties of components such as proteins, which in turn can lead to the development of new products. Equipment for large-scale production of HHP processed products are commercially available nowadays. Guacamole, sliced ham, oysters, and fruit juices are some of the products currently available on the market. HHP technology is one of the most promising nonthermal processes.     

Microbiological food safety assessment of high hydrostatic pressure processing: A review

High hydrostatic pressure (HHP) processing as a novel non-thermal method has shown great potential in producing microbiologically safer products while maintaining the natural characteristics of the food items. Scientific research of the process and its industrial applications has been widespread in the past two decades with many scientific publications describing its uses, advantages and limitations. The review describes the effect of HHP on foodborne pathogenic microorganisms, their structures and adaptive mechanisms, the intrinsic and extrinsic factors that affect its application with a focus on microbiological safety, and research needs. In a risk assessment context, tools and mechanisms in place to monitorize, optimize and validate the process, and procedures for assessing and modelling the lethal effect of the treatment are reviewed.     

高静压在脱敏食品中的应用研究

高静压可以改变食物的结构和功能特性,掩盖食物过敏原的抗原表位,从而降低食物的过敏原性,被广泛应用于脱敏食品的加工过程中。阐述了食品脱敏的必要性,介绍了食品过敏原种类、作用机理及发病机理,综述了近几年高静压在食品脱敏中的应用。     

Bacterial inactivation by high-pressure homogenisation and high hydrostatic pressure

The resistance of five gram-positive bacteria, Enterococcus faecalis, Staphylococcus aureus, Lactobacillus plantarum, Listeria innocua and Leuconostoc dextranicum, and six gram-negative bacteria, Salmonella enterica serovar typhimurium, Shigella flexneri, Yersinia enterocolitica, Pseudomonas fluorescens and two strains of Escherichia coli, to high-pressure homogenisation (100-300 MPa) and to high hydrostatic pressure (200-400 MPa) was compared in this study. Within the group of gram-positive bacteria and within the group of gram-negative bacteria, large differences were observed in resistance to high hydrostatic pressure, but not to high-pressure homogenisation. All gram-positive bacteria were more resistant than any of the gram-negative bacteria to high-pressure homogenisation, while in relative to high hydrostatic pressure resistance both groups overlapped. Within the group of gram-negative bacteria, there also existed another order in resistance to high-pressure homogenisation than to high hydrostatic pressure. Further it appears that the mutant E. coli LMM1010, which is resistant to high hydrostatic pressure is not more resistant to high-pressure homogenisation than its parental strain MG1655. The preceding observations indicate a different response of the test bacteria to high-pressure homogenisation compared to high hydrostatic pressure treatment, which suggests that the underlying inactivation mechanisms for both techniques are different. Further, no sublethal injury could be observed upon high-pressure homogenisation of Y. enterocolitica and S. aureus cell population by using low pH (5.5 7), NaCl (0 6%) or SDS (0-100 mg/l) as selective components in the plating medium. Finally, it was observed that successive rounds of high-pressure homogenisation have an additive effect on viability reduction of Y. enterocolitica and S. aureus.     

Physiological damages of Listeria monocytogenes treated by high hydrostatic pressure

A fluorescent glucose analogue, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose (2-NBDG), which had been developed previously for the analysis of glucose uptake activity by living cells, was investigated to evaluate its applicability for assaying the viability of yeasts. Fluorescence intensities of the yeast population were measured by fluorescence spectrophotometry upon exposure to antifungal agents after staining with 2-NBDG and were compared to the number of colony forming units (CFU). A good correlation was obtained between the yeast viability, determined by the CFU, and the accumulation of 2-NBDG by yeast cells (correlation constant: r=0.98). Susceptibility testing of amphotericin B and miconazole against yeast strains by plate count and 2-NBDG fluorescence method yielded corresponding results. In conclusion, we found that staining with 2-NBDG is a rapid and sensitive method for the assessment of yeast cell viability.     

Enhancement of anti-inflammatory and antioxidant activities of prickly pear fruits by high hydrostatic pressure: A chemical and microstructural approach

Prickly pears were submitted to high hydrostatic pressure (HHP) (pressure: 100, 350 and 600 MPa; temperature: 17–34 °C; time: come-up time (CUT) and 5 min) to enhance their health potential by increasing the extractability of bioactive compounds. Phenolics, betalains and ascorbic acid were analyzed by high performance liquid chromatography (HPLC) and spectrophotometry in peels and in pulps to determine their contribution to in-vitro bowel-related antioxidant (oxygen radical absorbance capacity; ORAC) and anti-inflammatory activities (hyaluronidase inhibition and nitric oxide radical scavenging activity). Antioxidant activity in Pelota and Sanguinos pulps increased 81.1 and 68.2% at 350 MPa/5 min, respectively, and correlated with the increase of phenolic acids, isorhamnetin glucosyl-rhamnosyl-rhamnoside (IG1) and isorhamnetin glucosyl-rhamnoside (IG5). Anti-inflammatory activity increased 85.7 and 117.5% in Pelota and Sanguinos pulps, respectively, at 600 MPa/CUT and correlated with the increase of isorhamnetin glucosyl-rhamnosyl-pentoside (IG2), isorhamnetin glucosyl-pentoside (IG4) and IG5.Industrial relevancePrickly pears are potential sources of low-cost functional foods because they are rich in valuable bioactive compounds. However, these are only partially bioaccessible because they compartmentalized within cellular structures and bound to cell walls. By processing with high hydrostatic pressure, we can obtain fruit products with a higher bioactive content. This potentially enhances bowel-related antioxidant and anti-inflammatory activities. These results take us one step closer to the prevention of chronical diseases with the consumption of our everyday foods. The use of non-thermal technologies for the enhancement of health potential in vegetable foods could result in a useful tool for the development of the novel foods of the 21st century.     

超高压对食品中微生物的影响

超高压是一种新型食品加工技术,已广泛应用于食品的非热加工。在超高压条件下微生物的细胞壁、细胞膜被破坏,引起细胞形态结构的改变;微生物细胞内的结构蛋白、酶等在超高压条件下被钝化,导致微生物正常的代谢功能和增殖能力被破坏;在超高压条件下微生物的蛋白组和基因组也产生了一定的变化,许多与抗逆有关的蛋白质和基因表达上调。     

Effect of high hydrostatic pressure on starches: A review

Various strategies have been employed to enhance starch property, including thermal processing, chemical modification. The application of high hydrostatic pressure (HHP) may be a complementary, synergistic, or an additive starch enhancement technique. While most current applications of HHP are in starch processing, over 25 starches had been investigated by HHP, which can induce gelatinization and modification of some starches. Different starch responds differently to high pressure depending on the pressure range, starch source, pressurization temperature and time, different solvent and starch concentration. We have re‐examined the information on the various factors that influence the HHP‐induced structure, gelatinization, retrogradation, and modification of starches from different plant sources, with an emphasis on the HHP‐induced gelatinization. The compiled evidence of high pressure starch enhancement in this paper indicates that HHP is an effective technology with potential for greater utilization in starch application.     

Maillard-type reactions under high hydrostatic pressure: Formation of pentosidine

Application of hydrostatic pressure up to 600 MPa on a solution consisting of N ^α -acetylarginine, N ^α -acetyllysine and ribose in equimolar ratios (pH 7.4, T=60 °C, t=2 h) resulted in a pressure-dependent increase of the pentosidine content. This marker for the advanced Maillard reaction could also be found protein-bound in enhanced yields by increasing pressure on β-casein incubated with ribose in solution. Received: 4 January 2000     

Activation and inactivation of Talaromyces macrosporus ascospores by high hydrostatic pressure

The effect of high hydrostatic pressure treatment (with pressures of up to 700 MPa) on Talaromyces macrosporus ascospores was investigated. At 20 degrees C, pressures of > or = 200 MPa induced the activation and germination of dormant ascospores, as indicated by increased colony counts for ascospore suspensions after pressure treatment and the appearance of germination vesicles and tubes. Pressures of > 400 MPa additionally sensitized the ascospores to subsequent heat treatment. At pressures of > 500 MPa, activation occurred in a few minutes but was followed by inactivation with longer exposure. However, even with the most extreme pressure treatment, a fraction of the ascospore population appeared to resist both activation and inactivation, and the maximal achievable reduction of ascospores was on the order of 3.0 log10 units. Pressure-induced ascospore activation at 400 MPa was temperature dependent, with minimum activation at 30 to 50 degrees C and > or = 10-fold higher activation levels at 10 to 20 degrees C and at 60 degrees C, but it was not particularly pH dependent over a pH range of 3.0 to 6.0. Pressure inactivation at 600 MPa, in contrast, was pH dependent, with the inactivation level being 10-fold higher at pH 6.0 than at pH 3.0. Observation of pressure-treated and subsequently dried spores with the use of light and scanning electron microscopy revealed a collapse of the spore structure, indicating a loss of the spore wall barrier properties. Finally, pressure treatment sensitized T. macrosporus ascospores to cell wall lytic enzymes.     

Anthocyanin condensation reactions under high hydrostatic pressure

The effects of temperature and/or high hydrostatic pressure on anthocyanin condensation reactions were studied. For this purpose, model solutions containing cyanidin-3-O-glucoside (Cy3gl) and pyruvate, in excess, were subjected to different combined temperature/pressure treatments. After a high hydrostatic pressure treatment of 600 MPa, at 70 °C during 30 min, about 25% of Cy3gl was degraded. Parallel to this decrease, a vitisin A-type derivative was formed. By contrast, the rate of condensation was only 5% when samples were heated (70 °C, 30 min). In both cases, the degradation kinetics fitted well to a first order reaction (R² = 0.99). The decrease in Cy3gl was correlated with a decrease in the antioxidant activity. Moreover, the chemical stability of wine subjected to a temperature/pressure treatment of 600 MPa, at 70 °C during 1 h was investigated. After this treatment, a decrease in the concentration of malvidin-3-O-glucoside (Mv3glu) was found. As a consequence, an increase in the concentration of several products of high molecular weight at 370 nm was observed. When wine was subjected to pasteurization conditions (600 MPa, 70 °C, 10 min), no significant changes in the chemical composition were found (P < 0.05).     

Functional improvement of milk whey proteins induced by high hydrostatic pressure

High pressure is emerging as a new processing technology that produces particular changes in the molecular structure of proteins and thus gives rise to new properties inaccessible via conventional methods of protein modification. This review deals with the main effects of high hydrostatic pressure on the physicochemical characteristics of milk whey proteins and how modifications in their structural properties contribute to functionality. In this paper the mechanism underlying pressure-induced changes in ss-lactoglobulin, a-lactabumin, and bovine serum albumin is explained, and related to functional properties such as gel-forming ability, emulsifying activity, or foaming capacity. The possibility of using high pressures to favor chemical reactions of proteins with other food components, such as carbohydrates, to produce novel molecules with new food uses is also considered.     

Decontamination of seeds for seed sprout production by high hydrostatic pressure

Garden cress, sesame, radish, and mustard seeds immersed in water were treated with high pressure (250, 300, 350, and 400 MPa) for 15 min at 20 degrees C. After treatment, percentages of seeds germinating on water agar were recorded for up to 11 days. Of the seeds tested, radish seeds were found to be the most pressure sensitive, with seeds treated at 250 MPa reaching 100% germination 9 days later than untreated control seeds did. Garden cress seeds, on the other hand, were the most pressure resistant, with seeds treated at 250 MPa reaching 100% germination 1 day later than untreated control seeds did. Garden cress sprouts from seeds treated at 250 and 300 MPa also took about 1 day longer to reach average sprout length than sprouts from untreated control seeds did, indicating that sprout growth was not retarded once germination had occurred. Garden cress seeds were inoculated with suspensions of seven different bacteria (10(7) CFU/ml) and processed with high pressure. Treatment at 300 MPa (15 min, 20 degrees C) resulted in 6-log reductions of Salmonella Typhimurium, Escherichia coli MG1655, and Listeria innocua, > 4-log reductions of Shigella flexneri and pressure-resistant E. coli LMM1010, and a 2-log reduction of Staphylococcus aureus. Enterococcus faecalis was virtually not inactivated. For suspensions of the gram-positive bacteria, similar levels of inactivation in water in the absence of garden cress seeds were found, but the inactivation of E. coil LMM1010 and S. flexneri in water in the absence of garden cress seeds was significantly less extensive. These data suggest that garden cress seeds contain a component that acts synergistically with high hydrostatic pressure against gram-negative bacteria.     

Inactivation of avian influenza virus by heat and high hydrostatic pressure

Avian influenza viruses threaten the life of domestic terrestrial poultry and contaminate poultry meat and eggs. Recently, these viruses rarely infected humans but had a high mortality rate in Southeast Asia, the Middle East, and Egypt. Thereby, these viruses caused high economic costs for production of poultry and health protection. We inactivated a highly pathogenic avian influenza A virus of subtype H7N7 in cell culture medium and chicken meat by heat and high hydrostatic pressure. Because heat and pressure inactivation curves of the H7N7 virus showed deviations from first-order kinetics, a reaction order of 1.1 had to be selected. A mathematical inactivation model has been developed that is valid between 10 and 60 degrees C and up to 500 MPa, allowing the prediction of the reduction in virus titer in response to pressure, temperature, and treatment time. Incubation at 63 degrees C for 2 min and 500 MPa at 15 degrees C for 15 s inactivated more than 10(5) PFU/ml, respectively. Thus, we suggest high-pressure treatment of poultry and its products to avoid the possible health threat by highly pathogenic avian influenza viruses.     

Enhancing enzymatic hydrolysis of food proteins and production of bioactive peptides using high hydrostatic pressure technology

BackgroundBioactive peptides (BPs) generated by hydrolysis of food proteins exhibit a broad spectrum of biological properties (antihypertensive, hypocholesterolemic, antimicrobial, antioxidant, etc.) in both in vitro and in vivo models. Initially obtained from milk and egg products, BPs have now largely been obtained from food byproducts such as marine, animal and plant biomasses. Amongst the various strategies being developed for BPs production, enzymatic hydrolysis (EH) is the most widely preferred due to its GRAS nature. However, the main challenge of EH is to decrease the time and quantity of enzyme, and improve yield and bioactivity of BPs.Scope and approachConsequently, innovative and efficient food technologies have been developed to satisfy these needs. High hydrostatic pressure (HHP) processing, a non-thermal technology, initially developed to extend food shelf-life, is being considered as a promising tool to improve the efficiency of EH and generate high value-added peptide fractions from various complex biomasses.Findings and conclusionsThis innovative and emerging technology enhances EH by inducing protein unfolding/denaturation, as well as activating the enzymes used while maintaining their nutritional and functional properties. This review discusses the state of the art of HHP technique, its applications in combination with EH, and potential challenges for the production of BPs from food-derived protein sources.     

Inactivation ofEscherichia coliinoculated in liquid whole egg by high hydrostatic pressure

The resistance ofEscherichia coliin liquid whole egg was studied at several pressures (300, 350, 400 and 450MPa), temperatures (50, 20, 2 and –15°C) and times (5, 5+5, 10, 5+5+5, 15min). The highest reduction was obtained at 50°C (about 7log₈units). At 20 and –15°CE. coliwas more resistant to pressure than at 50 and 2°C. The intermittent treatments were more effective than continuous treatments at lower pressures (350MPa). The destruction increases upon increasing the pressure and the time treatment. Survivor curves were studied at 400MPa for two temperatures (20 and 2°C) and different times (0–60min), obtaining a decimal reduction time of 14.1min at 20°C and 9.5min at 2°X.     

Inactivation of Bacillus cereus spores by high hydrostatic pressure at different temperatures

The effect of pH on the initiation of germination and on the inactivation of Bacillus cereus (KCTC 1012) spores during high hydrostatic pressure processing (HPP) with pressures of 0.1 to 600 MPa at different temperatures was investigated. Two different high-pressure treatments were adopted to evaluate the effect of pH on the inactivation of B. cereus on sporulation medium and in suspension medium. Inactivation of B. cereus spores with HPP treatment was affected more by sporulation medium pH than by suspension medium pH. B. cereus spores obtained through sporulation at pH 6.0 showed more resistance to inactivation by HPP at 20, 40, and 60 degrees C than did those obtained through sporulation at pHs of 7.0 and 8.0. Constituents of B. cereus spores obtained through sporulation at pH 6.0 may undergo electrochemical charge changes comparable to those for spores obtained through sporulation at pH 7.0. The initiation of B. cereus spore germination was more sensitive to pressure around 300 MPa at 20 degrees C. Increasing processing temperatures during HPP enhanced the effect of sporulation medium pH (i.e., environmental pH) on the inactivation of B. cereus spores.