Impact Of High Hydrostatic Pressure Research Articles

Impact of High Hydrostatic Pressure on Protein Aggregation and Rheological Properties of Legume Batters

The impact of high hydrostatic pressure (HP) treatment on protein aggregation and rheological properties of legume batters has been investigated. Gelatinisation/pasting and gelling profiles, rheological parameters and protein solubility of HP-hydrated chickpea (CP), green pea (GP) and soybean (SB) flours were determined. CP, GP and SB hydrated flours, at dough yield (DY) 160 and 200, were treated for 10 min at 0.1, 200, 350 or 450 MPa. Pressures of ≥350 MPa downward shifts gelatinisation temperatures in CP and GP regardless the hydration level. For all legume batters, HP provokes changes on the rheology of hydrated samples, particularly in softer batters (DY 200), leading to an increased stiff/solid character. Analysis of proteins extracted in different buffers revealed that pressures of >200 MPa induced the formation of urea-insoluble complexes, disulphide bonds and/or other strong protein aggregates. Although the extent of protein modification was dependent on the applied pressure, the results collected so far show that high HP can be used to improve the breadmaking functionality of CP, GP and SB batters.

Impact of High Hydrostatic Pressure and Heat Treatments on Milk Gel Properties: A Comparative Rheological Study

The effects of high hydrostatic pressure (483 and 676 MPa at 20°C for 5 min) and heat treatment (63°C for 30 min and 72°C for 15 s) of milk on the rheological properties of coagulant-induced milk gels were investigated. The rheological properties of gels were determined using a dynamic Physica Rheometer and Texture Analyzer. Milk turbidity was measured by a spectrophotometer. The gels produced from a pressure of 483 MPa had higher storage modulus (G*) and firmer gel at cutting compared to heated milks. Increasing the pressure to 676 MPa caused a reduction in G*, less firm gels, and an increase in milk turbidity compared to 483 MPa and heated milks. The differences between the gels formed from different pressure- and heat-treated milks, suggesting that the structure network of gels were considerably altered by high hydrostatic pressure treatment of milk. Disruption of casein micelles and denaturation of whey proteins caused by high hydrostatic pressure treatments were responsible for most of the effects observed in this study. In general, pressurizing the milk at 483 MPa at 20°C was a promising treatment for the manufacture of coagulant-induced milk gels with good rheological properties; however, pressurization at 676 MPa could not be recommended.

Promoting dough viscoelastic structure in composite cereal matrices by high hydrostatic pressure

The impact of high hydrostatic pressure (HP) treatment on dough viscoelastic reinforcement of highly-replaced wheat cereal matrices has been investigated. The gelatinisation/pasting and gelling profiles of HP hydrated oat, millet, sorghum and wheat flours, and the small and large deformation rheological parameters of blended wheat/non-wheat doughs were determined. Oat, millet, sorghum and wheat hydrated flours, at dough yield (DY) 160 and 200, were treated for 10min at 0.1, 200, 350 or 500MPa. Regardless the nature of the cereal, HP changes flour viscometric features, particularly in softer doughs (DY 200), leading to increased values for viscosity parameters, concerning pasting and paste cooking. Incorporation of 350MPa pressure-treated flours into bread dough formulation provided increased dynamic moduli values, particularly for wheat and oat/wheat blends, associated to a reinforced dough structure. Highly-replaced composite dough samples treated at 500MPa proved to be extremely stiff, resistant to stretch, low cohesive and low extensible, and thus not suitable for breadmaking.

Impact of High Hydrostatic Pressure on the Emulsifying Properties of Whey Protein Isolate–Chitosan Mixtures

The influence of high hydrostatic pressure (HHP) on the emulsifying properties of whey protein isolate (WPI) and chitosan mixtures in sunflower oil-in-water emulsion has been investigated at pH 4.0. WPI and chitosan mixtures at various ratios were treated at pressure levels in the range of 0–600 MPa for 10–30 min. The emulsifying properties of the mixtures were analyzed by dynamic light scattering and a centrifugal sedimentation technique. HHP treatments of the mixtures resulted in improvement in their emulsifying properties, with the emulsions formed showing more than threefold reductions in droplet size, much more homogeneous droplet distribution, and better creaming stability. The higher the treatment pressure was, the smaller the droplet size and more stable the emulsions were, with those prepared with the mixtures treated at 600 MPa showing no noticeable creaming after 30 days of storage at ambient temperature. The ratio of WPI to chitosan and treatment time also affected the emulsification stability of the mixtures, with a WPI to chitosan ratio of 1:4 (w/w) and treatment time of 20 min found to be the optimum conditions. These results showed that HHP could be a useful method for enhancing the emulsifying properties of protein–polysaccharide mixtures.

High hydrostatic pressure can improve the microbial quality of sauerkraut during storage

The impact of high hydrostatic pressure (HHP) on the microbial quality of sauerkraut during refrigerated storage for 1–3 months was evaluated. Sauerkraut was obtained from white cabbage by natural or induced fermentation at two salt concentrations (0.5% or 1.5% NaCl). The fermentation decreased the number of total coliforms, and increased aerobic mesophilic bacteria and LAB counts, and the greatest levels were found in induced fermentation. During storage, a gradual rise of aerobic mesophilic bacteria and LAB was observed and 0.5% NaCl caused higher counts than 1.5% NaCl at the end of the storage period. HHP led to a reduction in microbial counts (4–5 log cfu/g) and storage brought about an increment in aerobic mesophilic bacteria and LAB, always reaching significant lower counts than in unpressurised sauerkraut stored for the same period. Hence, HHP can be considered as an efficient method to improve the microbial quality and shelf-life of sauerkraut.

Mechanism and Related Kinetics of 5-Methyltetrahydrofolic Acid Degradation during Combined High Hydrostatic Pressure−Thermal Treatments

The mechanism and kinetics of the degradation of 5-methyltetrahydrofolic acid during thermal and combined high pressure-thermal treatments in an aqueous solution were investigated. In a first approach the degradation was described by a first-order kinetic model using single-response modeling, and the combined pressure-temperature dependence of the resulting degradation rate constants was empirically described. To obtain a mechanistic insight, degradation products were purified and identified by LC-MS and NMR. Quantification of an s-triazine derivative, 5-methyldihydrofolic acid, and p-aminobenzoyl-l-glutamate as predominant degradation products at atmospheric pressure resulted in elucidation and kinetic characterization of the folate degradation mechanism by Bayesian multiresponse modeling. The postulated mechanism was evaluated at elevated hydrostatic pressure. On the basis of the pressure and temperature dependence of the reaction rates, some degradation reactions were either accelerated or decelerated upon application of pressure. Multiresponse kinetics can be a valuable tool to assess the impact of high hydrostatic pressure and other processing techniques on nutrients, and incorporating mechanistic insights can advance the current kinetic approach for process optimization.

Inactivation kinetics of apple polyphenol oxidase in different pressure–temperature domains

The impact of high hydrostatic pressure and temperature on the stability of polyphenol oxidase (PPO) was studied in cloudy apple juice. Application of 200–500 MPa near room temperature or heat treatment at 45–55 °C at ambient pressure caused an increase of PPO activity of up to 65% in freshly squeezed apple juice. Combined pressure–temperature inactivation experiments with fully activated PPO (5 min treatment at 400 MPa and 20 °C) were carried out in the range of 0.1–700 MPa and 20–80 °C. Enzyme inactivation kinetics followed a 2.2 order reaction scheme at all pressure–temperature conditions tested. A polynomial model was successfully applied to describe the rate of PPO inactivation as a function of pressure and temperature and was used to construct a pressure–temperature isokinetic diagram. This diagram clearly showed synergistic effects of pressure and temperature on the inactivation of apple PPO at pressures above 300 MPa and antagonistic effects at lower pressures. Compared to ambient pressure conditions, temperatures required to inactivate PPO in apple juice were increased 10–15 °C at 100–300 MPa. High pressure processing of fresh fruits is gaining popularity in the food industry because of its ability to inactivate microorganisms and some enzymes near room temperature with little impact on flavour or nutritional attributes of the food. However, quantitative data regarding the impact of process parameters on the target reaction are required to economically utilise this technology. This paper provides a mathematical model describing the combined effect of pressure, temperature and treatment time on the inactivation of PPO in cloudy apple juice.

Defining the stability interfaces of apple juice: Implications on the optimisation and design of High Hydrostatic Pressure treatment

Abstract In this article an experimental approach is applied to determine the impact of High Hydrostatic Pressure (HHP) processing (350 to 550 MPa at 20 °C and for 1 to 25 min of holding time) on the survival of Issatchenkia orientalis and the spoilage of apple juice (with 300 ppm added ascorbic acid) during different storage conditions, i.e., 4 to 12 °C and 0 to 36 days of storage. Probabilistic modelling approaches based on logistic regression models were developed in order to describe quantitatively the spoilage/no spoilage and survival/death interfaces. For a microbially stable processed apple juice treated at 400 MPa, 10 °C and a holding time of 15 min the degradation kinetics of vitamin C were described quantitatively during subsequent storage at 4, 8, 12 °C. The rate of vitamin losses were highly reduced after the first 13 days of storage. The stability of the apple juice with respect to browning and cloudiness was evaluated by studying qualitatively the activity of polyphenol oxidase (PPO), and pectin methyl esterase (PME) enzymes at combined treatments of HHP and temperature (10 to 50 °C, HHP at 750 MPa and holding time from 1 to 25 min). The highest achieved reduction of PPO and PME was 51.47% and PME 81.44%, respectively. Industrial relevance This paper demonstrates an approach based on quantitative probabilistic and qualitative studies for defining the stability interfaces of apple juice. Its applicability contributes on the design and optimisation of High Hydrostatic Pressure treatments.

Fundamental evaluation of the impact of high Hydrostatic Pressure on oat batters

The use of grains alternative to wheat or rye is a challenging task for cereal technologists, and currently new technologies are under investigation as tools to improve the performances of these alternative grains. In this work the effects of high Hydrostatic Pressure (HP) on oat batters were investigated. Oat batters were treated for 10 min at 200, 300, 350, 400 or 500 MPa. Scanning electron microscopy and bright field microscopy showed that high HP significantly affected oat batter microstructure, and both starch and proteins were affected. Treatment at high HP significantly improved batter viscosity and elasticity. At pressures ≤300 MPa the increase in the viscous component was higher than the increase in the elastic component. On the contrary, at pressures ≥350 MPa the elastic component was predominant. Differential scanning calorimetry revealed that high HP induced starch gelatinisation, which started at 300 MPa and was almost complete after treatment at 500 MPa. High HP also affected water- and salt-soluble as well as urea-soluble oat proteins. Analysis of proteins soluble in different buffers revealed that pressures ≥300 MPa induced the formation of urea-insoluble complexes and/or disulfide bonds. Overall, the extent of starch gelatinisation and protein modification was dependent on the applied pressure, but the results collected so far clearly show that high HP can be used to improve the functionality of oat batters.

High Hydrostatic Pressure Modification of Whey Protein Concentrate for Improved Body and Texture of Lowfat Ice Cream

Previous research demonstrated that application of high hydrostatic pressure (HHP), particularly at 300MPa for 15min, can enhance foaming properties of whey protein concentrate (WPC). The purpose of this research was to determine the practical impact of HHP-treated WPC on the body and texture of lowfat ice cream. Washington State University (WSU)-WPC was produced by ultrafiltration of fresh separated whey received from the WSU creamery. Commercial whey protein concentrate 35 (WPC 35) powder was reconstituted to equivalent total solids as WSU-WPC (8.23%). Three batches of lowfat ice cream mix were produced to contain WSU-WPC without HHP, WSU-WPC with HHP (300MPa for 15min), and WPC 35 without HHP. All lowfat ice cream mixes contained 10% WSU-WPC or WPC 35. Overrun and foam stability of ice cream mixes were determined after whipping for 15min. Ice creams were produced using standard ice cream ingredients and processing. The hardness of ice creams was determined with a TA-XT2 texture analyzer. Sensory evaluation by balanced reference duo-trio test was carried out using 52vol.nteers. The ice cream mix containing HHP-treated WSU-WPC exhibited the greatest overrun and foam stability, confirming the effect of HHP on foaming properties of whey proteins in a complex system. Ice cream containing HHP-treated WSU-WPC exhibited significantly greater hardness than ice cream produced with untreated WSU-WPC or WPC 35. Panelists were able to distinguish between ice cream containing HHP-treated WSU-WPC and ice cream containing untreated WPC 35. Improvements of overrun and foam stability were observed when HHP-treated whey protein was used at a concentration as low as 10% (wt/wt) in ice cream mix. The impact of HHP on the functional properties of whey proteins was more pronounced than the impact on sensory properties.

High pressure phase transition kinetics of maize starch

In this paper, the impact of high hydrostatic pressure, temperature and time on the gelatinization of maize starch is reported. Starch transition has been assessed by microscopic inspections of the granule’s loss in birefringence which occurs during the first stage of gelatinization in consequence of the water uptake. Experiments have been carried out under combined pressure–temperature treatments in the range of 0.1–650 MPa and 30–75 °C. The rate of gelatinization has been determined by an interpolating model and isokineticity lines were plotted in pressure–temperature diagrams. Pressure higher than 300 MPa is necessary to reduce significantly the onset temperature of gelatinization. At those pressures, the isokineticity lines are bended to the left, indicating that the phase transition in birefringence is occurring at lower temperatures. At 30 °C, maize starch was gelatinized completely after 30 min at 650 MPa.

Stability and catalytic activity of α‐amylase from barley malt at different pressure–temperature conditions

The impact of high hydrostatic pressure and temperature on the stability and catalytic activity of alpha-amylase from barley malt has been investigated. Inactivation experiments with alpha-amylase in the presence and absence of calcium ions have been carried out under combined pressure-temperature treatments in the range of 0.1-800 MPa and 30-75 degrees C. A stabilizing effect of Ca(2+) ions on the enzyme was found at all pressure-temperature combinations investigated. Kinetic analysis showed deviations of simple first-order reactions which were attributed to the presence of isoenzyme fractions. Polynomial models were used to describe the pressure-temperature dependence of the inactivation rate constants. Derived from that, pressure-temperature isokinetic diagrams were constructed, indicating synergistic and antagonistic effects of pressure and temperature on the inactivation of alpha-amylase. Pressure up to 200 MPa significantly stabilized the enzyme against temperature-induced inactivation. On the other hand, pressure also hampers the catalytic activity of alpha-amylase and a progressive deceleration of the conversion rate was detected at all temperatures investigated. However, for the overall reaction of blocked p-nitrophenyl maltoheptaoside cleavage and simultaneous occurring enzyme inactivation in ACES buffer (0.1 M, pH 5.6, 3.8 mM CaCl(2)), a maximum of substrate cleavage was identified at 152 MPa and 64 degrees C, yielding approximately 25% higher substrate conversion after 30 min, as compared to the maximum at ambient pressure and 59 degrees C.