Hydrostatic Pressure Processing Research Articles

Bacterial biofilm formation in seafood: Mechanisms and inhibition through novel non‐thermal techniques

AbstractSeafoods are susceptible to microbial contamination due to their high moisture, nutrient contents and neutral pH. Among various microorganisms, biofilm‐forming bacteria pose a severe threat to the seafood supply chain as well as consumer health. Bacterial biofilm formation in seafood is primarily caused by Aeromonas hydrophila, Vibrio cholerae, V. vulnificus, V. parahaemolyticus, Salmonella spp., and Listeria monocytogenes. Biofilm formation is an important protective mechanism of microorganisms causing spoilage of seafood and disease threats to consumers. The attachment of microbes on the surface of seafood followed by the growth and proliferation of bacterial cells leads to the production of exopolymer compounds and the formation of biofilm. This biofilm is difficult to destroy or inhibit through conventional prevention/destruction techniques. The occurrence of bacterial strains/biofilms with more resistance to different preventive strategies is a big challenge for the seafood processing industry. This review covers the mechanisms of biofilm formation by bacteria and various non‐thermal processing approaches to prevent microbial contamination and biofilm formation in seafood products. The aforementioned non‐thermal processing techniques for the destruction of biofilm and quality control of seafood products include cold plasma treatment, irradiation, pulsed electric field technology, hydrostatic pressure processing, photosensitisation, natural bioactive compounds and so on. All these techniques effectively inhibit the bacterial biofilm and microbial growth without altering sensorial properties. However, further research validation and applications at the industry level are still required.

Simultaneous application of hydrostatic pressure and microbial transglutaminase as pretreatment to improve the physicochemical properties of heat-induced gels from tilapia surimi paste

Tilapia pastes were subjected to pretreatment using a combination of hydrostatic pressure processing (HPP) (0.1 to 300 MPa/25°C/60 mm) and simultaneous addition of microbial transglutaminase (MTGase) (0.044 unit/g of paste), which was followed by cooking at 90°C for 20 mm, to investigate the changes in the physicochemical properties of heat-induced gels. The pretreatment with MTGase at 300 MPa produced a gel having the strongest breaking force and strain compared with all the other treatments in the study; the gel strength was 3.5 times higher than that of the gel obtained by the 300 MPa treatment without adding MTGase. The combined use of MTGase and HPP for pretreatment could also improve the water-holding capacity of the gel, the value of which ranged from 63.12 to 89.34%. Adding MTGase also could decrease protein solubility under different pressure treatments. Thus, pretreatment of the sample is a better way to improve the gel-forming ability of tilapia surimi.

High hydrostatic pressure stabilized micronutrients and shifted dietary fibers, from insoluble to soluble, producing a low-glycemic index mango pulp

ABSTRACT Nutritional authorities state that both total carbohydrates and low glycemic index (GI) diets affect glycemic control. High hydrostatic pressure (HHP) processing reduced the GI response of mango pulp when consumed by healthy adults. Present work evaluated the effects of HHP processing on concentrations of mango pulp dietary fiber sub-fractions (AOAC 2011.25 method), pectin methyl esterase (PME) activity, and established links with reduction of GI responses in healthy adults. Processing stability of mango pulp micronutrients (carotenoids, phenolics, ascorbic acid, and antioxidant activity) were also assessed. HHP-processing caused fiber inter-conversions from insoluble to soluble dietary fiber, the latter being significantly higher. Concentrations of non-digestible oligosaccharides and PME activities were also higher in treated pulps. In addition, HHP-processing preserved relevant mango phytonutrients such as carotenoids and phenolic compounds. Micronutrient retention and dietary fiber modifications suggested that HHP-processing improved mango pulp benefits for healthy subjects and potentially for patients with chronic metabolic diseases.

High pressure processing of carrot juice: Effect of static and multi-pulsed pressure on the polyphenolic profile, oxidoreductases activity and colour

The aim of this study was to determine the influence of static and multi-pulsed hydrostatic pressure processing (HPP) treatments on the polyphenolic profile, oxidoreductase activity, colour, and browning index of carrot juice. Phenolic acids, flavonoids, lignans and other polyphenols were the predominant polyphenols detected with Triple-TOF-LC-MS/MS. The highest concentration of ferulic acid, didymin, dihydro-p-coumaric acid, sesaminol and matairesinol isomers were found among all the compounds detected. After HPP treatment, irrespective of the pressures applied, new simple polyphenols like oleuropein, 4-vinylsyringol, isocoumarin, and 4-hydroxybenzaldehyde were detected. Both phenomena could be attributed to the release of bounded phenolic compounds after applying HPP, as well as enzymatic degradation and/or condensation. The highest inactivation of polyphenoloxidase (PPO) enzymes (57%) was obtained at 300 MPa × 3 pulses, and peroxidase (POD) enzymes (31%) at 600 MPa working in static mode. Significant changes in the colour parameters and browning index were observed in all HPP-treated juices.

Machinery Mold (Galactomyces geotrichum) Survival following Thermal and Hydrostatic Pressure Processing

The D-value for machinery mold at 55°C was determined to be 0.99 min. Differences in thermoresistance was minimal between cultures of varying ages. A >5-log reduction was achieved by pressure treatments of 300 MPa for 90 s.

High hydrostatic pressure inactivation of Lactobacillus plantarum cells in (O/W)-emulsions is independent from cell surface hydrophobicity and lipid phase parameters

ABSTRACTInactivation efficiency of high hydrostatic pressure (HHP) processing of food is strongly affected by food matrix composition. We investigated effects of fat on HHP inactivation of spoilage-associated Lactobacillus (L.) plantarum strains using defined oil-in-water (O/W)-emulsion model systems. Since fat-mediated effects on HHP inactivation could be dependent on interactions between lipid phase and microbial cells, three major factors possibly influencing such interactions were considered, that is, cell surface hydrophobicity, presence and type of surfactants, and oil droplet size. Pressure tolerance varied noticeably among L. plantarum strains and was independent of cell surface hydrophobicity. We showed that HHP inactivation of all strains tended to be more effective in presence of fat. The observation in both, surfactant-stabilized and surfactant-free (O/W)-emulsion, indicates that cell surface hydrophobicity is no intrinsic pressure resistance factor. In contrast to the presence of fat per se, surfactant type and oil droplet size did not affect inactivation efficiency.

Postharvest intervention technologies for safety enhancement of meat and meat based products; a critical review.

Globally, the demand for safe, healthy and nutritious meat and allied products possesses improved taste with extended shelf life is mounting. Microbial safety is among the imperative challenges that prevails in meat products because they provide an ideal medium for the growth of microorganisms particularly pathogenic bacteria. The incidence of these microbes can result quality deterioration of products leading towards food borne diseases when consumed by peoples. Several preservation technologies like chemical and biological interventions are effective to retard or inactivate the growth of micro-organisms most commonly related to food-borne diseases. Despite these, innovative approaches like hydrostatic pressure processing, active packaging, pulse electric field, hurdle approach and use of natural antimicrobials can be deployed to enhance the safety of meat and meat products. The objective of review is to describe the current approaches and developing technologies for enhancing safety of meat and allied meat products.

Effects of Hydrostatic Pressure Processing on Texture and Color of Zebu Beef

This study investigated the effect of hydrostatic pressure processing (HPP) on post-rigor mortis beef (Longissimus dorsi muscle, Nelore breed) relevant parameters, such as texture, cooking loss, and color. Pressures varying from 100 to 400 MPa at different times of pressurization (T1: time to reach set pressure, and T2: T1 plus 15 min) were applied, immediately followed by depressurization. Samples were evaluated for color, cooking loss, and tenderness. Both pressure level and pressurizing time had an effect on the color, cooking loss, and tenderness. Low-pressure levels (up to 200 MPa) had a smaller impact on color; nevertheless, it improved tenderness. The cooking loss increased with increased levels of pressure; however, by increasing pressure to 100 and 200 MPa immediately followed by pressure release (T1), no significant differences were observed when compared to the results from unpressurized samples. On the other hand, cooking loss was higher in the beef pressurized at all pressure levels for 15 min (T2). The results show that treatments using lower pressures (100 to 200 MPa) can potentially contribute to Zebu meat quality improvement.

Inactivation and recovery of Listeria monocytogenes, Salmonella enterica and Staphylococcus aureus after high hydrostatic pressure treatments up to 900 MPa.

High hydrostatic pressure (HP) processing is used in the food industry to enhance the safety and extend the shelf-life of food. Although a drastic decrease in microbial viability is achieved immediately after the application of HP treatments, under favorable conditions the injured bacteria can recover. The present study evaluated the inactivation and recovery of five strains of Listeria monocytogenes, Salmonella enterica and Staphylococcus aureus subjected to pressures of 400, 600, and 900 MPa under stressing and non-stressing conditions in a complex medium. Treatments at 400 and 600 MPa were found to greatly affect the viability of L. monocytogenes and S. enterica, but only a treatment of 5 min at 900 MPa decreased the levels of the three pathogens to below the detection limit (8-9 log units reduction). After HP treatment, not only the baroresistant S. aureus but also several replicates of L. monocytogenes and S. enterica strains recovered during subsequent incubation under favorable conditions. However, when HP was combined with low pH and nitrite but not with NaCl or lactate, the viability of pressurized S. aureus cells progressively decreased. As pathogenic bacteria can recover even after the application of very high pressure levels, the combination of HP with other hurdles for microbial growth, either intrinsically present in the food product or extrinsically applied, may be needed to guarantee the efficacy of technologies aimed at pathogen reduction and shelf-life extension.

Effect of High Hydrostatic Pressure Processing on Freely Suspended and Bivalve-Associated T7 Bacteriophage

The effectiveness of hydrostatic pressure processing (HPP) for inactivating viruses has been evaluated in only a limited number of studies, and most of the work has been performed with viruses freely suspended in distilled water. In this work, HPP inactivation of freely suspended and shellfish-associated bacteriophage T7 was studied. T7 was selected in hopes that it could serve as a model for animal virus behavior. Clams (Mercenaria mercenaria) and oysters (Crassostrea virginica) were homogeneously blended separately and inoculated with bacteriophage T7. The inoculated bivalve meat and the freely suspended virus samples were subjected to HPP under the following conditions: 2, 4, and 6 min at 241.3, 275.8, and 344.7 MPa pressure and temperatures of 29.4 to 35, 37.8 to 43.3, and 46.1 to 51.7°C. Reductions of 7.8 log PFU (100% inactivation) were achieved for freely suspended T7 at 344.7 MPa for 2 min at 37.8 to 43.3°C. At 46.1 to 51.7°C, T7 associated with either clams or oysters was inactivated at nearly 100% (>4 log PFU) at all pressure levels and durations tested. These results indicate that T7 is readily inactivated by HPP under the proper conditions, may be made more susceptible to HPP by mixing with shellfish meat, and may serve as a viable model for the response of several animal viruses to HPP.

Effects of pressure- and thermal-pasteurization on volatiles of some berry fruits

In principle, high hydrostatic pressure (HHP) processing offers the possibility to preserve berry products while affecting their volatile components less than heat pasteurization. Therefore, we performed preliminary investigations to compare effects of HHP treatment (600 MPa, 5 min, at ambient temperature) and heat pasteurization (80 °C, 5 min) on volatile composition of raspberry, strawberry and blackcurrant purees measured by ‘electronic nose’ at 25 °C. Changes in the head space volatiles could be monitored by this method. Taking into account the confusion matrix of the discriminant analysis, heat-treatment had a more significant effect on volatile compounds than HHP. So, application of HHP treatment can retain volatiles of berry products.

Changes of hen eggs and their components caused by non-thermal pasteurizing treatments II. Some non-microbiological effects of gamma irradiation or hydrostatic pressure processing on liquid egg white and egg yolk

Experiments were performed to study changes caused by irradiation or high hydrostatic pressure pasteurization of liquid egg white by differential scanning calorimetry, spectrofluorimetry, electronic nose measurements and NIR-spectrometry. The non-thermal pasteurization treatments were also assessed in relation to loss of carotenoid content, and lipid- and cholesterol oxidation of liquid egg yolk. Unlike radiation pasteurization, high pressure processing caused protein denaturation in egg white, which manifested in changes of its DSC-thermogram and intrinsic tryptophan fluorescence. Electronic nose testing showed changes of the head-space volatile composition of egg albumen, particularly as a function of radiation treatment. Both treatments caused changes in the NIR-spectrometric “fingerprint” of the liquid egg white. Various chemometric analyses of the results of the latter instrumental methods, particularly statistical techniques developed by the group of one of the co-authors of this article, demonstrat...

Effect of high‐pressure treatments on mechanical and functional properties of restructured products from arrowtooth flounder (Atheresthes stomias)

AbstractRestructured fish products from arrowtooth flounder (Atheresthes stomias), an abundant and subutilized species from the Gulf of Alaska, were obtained by hydrostatic pressure processing (HPP) at 400 and 600 MPa with 0–5 min pressure‐holding time. Minced fish meat was massaged with 20 g kg−1 salt at 10 °C during 5 min, stuffed in commercial sausage case and HPP‐treated. Raw and cooked (90 °C for 15 min) pressure‐treated gels were characterized by changes in mechanical properties (texture profile analysis and punch test), protein solubility, electrophoretic profile, expressible water and color. The mechanical properties of raw fish gels increased with pressure level and pressure‐holding time while solubility decreased. Myosin aggregation shown by SDS‐PAGE was associated with changes in mechanical and functional properties. The values for mechanical properties of heat‐induced gels were higher in cooked pressure‐treated samples than in the heat‐only control. Copyright © 2004 Society of Chemical Industry

Mechanistic studies on the inactivation of Saccharomyces cerevisiae by high pressure

High hydrostatic pressure (HP) processing is a technology that can be applied as a food preservation process. Here, we show that mild HP treatments, a typical example being 15 min 300 MPa at 25°C, leads to a change in the cell wall protein structure of Saccharomyces cerevisiae such that cells are sensitised towards a treatment with β-1,3-glucanase. A deletion mutant with an impaired trehalose synthesis showed a 2 log increased inactivation compared to its parent strain when treated for 15 min with 200 MPa pressure at 25°C. It is well known that trehalose protects yeast membranes. However, plasma membrane-related propidium iodide uptake did not correlate quantitatively with the observed decrease in colony-forming units. We concluded that the primary HP inactivation step of yeast cells presumably involves a perturbation of (intracellular) membranes.