The effect of high hydrostatic pressure on taste substance distribution in fresh green tea leaves

ABSTRACT

High hydrostatic pressure (HHP) can be an alternative method to steaming to inhibit enzymatic fermentation in green tea making process. However, the effect of HHP treatment on green tea taste is not clear. Thus, this study aimed to determine the effect of HHP on substances associated with green tea taste. Fresh green tea leaves were immediately treated with HHP at 300, 500, or 700?MPa for 10, 30, or 60 min at 25°C. The concentration of free amino acids, catechins, and caffeine in HHP-treated samples was quantified by LC-MS. The taste intensity of the samples was detected by taste sensors. HHP resulted in a high accumulation of free amino acids in green tea leaves, which was likely due to proteolysis. In particular, theanine synthesis may have been promoted by an increase in the concentration of substrates during HHP. Compared to steaming, HHP enhanced umami richness, and inhibited bitterness and astringency.     

Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.     

The effect of high hydrostatic pressure on the survival of Saccharomyces cerevisiae in model suspensions and beetroot juice

The inactivation of Saccharomyces cerevisiae NCFB 3191 using high hydrostatic pressure of 300 MPa at 20°C with a holding time of 0, 1, 5 and 10 min was investigated with model suspensions in phosphate-buffered saline and in beetroot juice. The reduction in S. cerevisiae NCFB 3191 in model suspensions was about 5 log after 10 min of pressurization, irrespective of the initial level of cell concentration in the samples (5.4–8.7 log cfu/mL). The baroprotective effect of beetroot juice on yeast cells during pressurization was observed; the reduction was lower and was only 3.5 log (the inoculum was 5.4 log cfu/mL). No sublethal injury among the surviving cells of the studied yeast strain was found.     

Effect of plating and incubation conditions on the detection of lactic acid bacteria after high hydrostatic pressure treatment

ABSTRACT

Lactic acid bacteria (Leuconostoc mesenteroides, Enterococcus faecalis, and Lactobacillus fermentum) were subjected to high hydrostatic pressures (HHPs) of 400 and 600?MPa at 25°C for 10?min in phosphate-buffered saline. Differential plating methods were applied to evaluate HHP-treated cell populations, assuming that healthy and injured cells during plate incubation survived maximum and minimal stress, respectively. The stress was altered by using several selective media in combination with aerobic or anaerobic incubation at 25°C or 30°C. E. faecalis was detectable after 600?MPa treatment while L. mesenteroides and L. fermentum were nondetectable. Specific combinations of incubation conditions were suggested to determine maximum and minimum viable counts of L. mesenteroides and E. faecalis. The difference between the maximum and minimum counts can be used to evaluate HHP-injured population with reduced risks to overestimate healthy and/or underestimate HHP-injured cells.     

Effects of high hydrostatic pressure on secondary structure and emulsifying behavior of sweet potato protein

In this study, secondary structures of sweet potato protein (SPP) after high hydrostatic pressure (HHP) treatment (200–600?MPa) were evaluated and emulsifying properties of emulsions with HHP-treated SPP solutions in different pH values (3, 6, and 9) were investigated. Circular dichroism analysis confirmed the modification of the SPP secondary structure. Surface hydrophobicity increased at pH 3 and decreased at 6 and 9. Emulsifying activity index at pH 6 increased with an increase in pressure, whereas emulsifying stability index increased at pH 6 and 9. Oil droplet sizes decreased, while volume frequency distribution of the smaller droplets increased at pH 3 and 6 with the HHP treatment. Emulsion viscosity increased at pH 6 and 9 and pseudo-plastic flow behaviors were not altered for all emulsions produced with HHP-treated SPP. These results suggested that HHP could modify the SPP structure for better emulsifying properties, which could increase the use of SPP emulsion in the food industry.     

Preparation of black soybean (Glycine max L) extract with enhanced levels of phenolic compound and estrogenic activity using high hydrostatic pressure and pre-germination

We investigated the influence of high hydrostatic pressure (HHP) treatment on the estrogenic properties and conversion of the phenolic compounds in germinated black soybean. The black soybean was germinated for two- or four-days, and then subjected to HHP at 0.1, 50, 100, or 150?MPa for 12 or 24?h. The highest total polyphenol content (3.9?mg GAE/g), flavonoid content (0.8?mg?CE/g), phenolic acid content (940?±?18.96?μg/g), and isoflavonone content (2600?μg/g) were observed after germination for four days and HHP treatment at 100?MPa for 24?h. In terms of isoflavone composition, the malonyl, acetyl and β-glycoside contents decreased, while the aglycone content increased with HHP. The highest proliferative effect (150%) is observed at four days germination and HHP treatment at 100?MPa. These results suggest that application of HHP may provide useful information regarding the utility of black soybean as alternative hormone replacement therapy.     

圆柱形超高静水压水听器设计与测试

(本文介绍了一种应用于20Hz~20kHz频段、最大工作深度5000米的超高静水压水听器,水听器敏感元件采用厚壁压电陶瓷圆管,高强度复合泡沫去耦,通过对敏感元件及水听器结构进行合理设计,保证水听器具有高的耐压强度。设计了一种圆柱形高静压耦合腔,根据耦合腔声学和力学条件,确定了腔体尺寸及厚度,在国内首次实现了最高50MPa压力下的水听器低频灵敏度测试。测试结果表明,水听器常压下接收灵敏度响应平坦,在常压到50MPa压力范围内,水听器低频接收灵敏度最大变化小于2dB,表明该型水听器具有良好的压力稳定性,可在深海资源勘测、深海通讯等方面获得广泛应用。)     

Inactivation of Staphylococcus aureus using high hydrostatic pressure

The aim of this work was to develop a high-pressure decontamination and sterilization process for pharmaceutical treatments as was developed in food processing in the late eighties. The lack of normalized biological indicators able to validate sterilizing treatments under high pressure led us to select representative pathogenic strains from flora and the European Pharmacopoeia. We selected the following four bacterial strains: Candida albicans (ATCC 10231), Psuedomonas aeruginosa (ATCC 9027), spores of Aspergillus niger (ATCC 16404) and Staphylococcus aureus (ATCC 6538).

This present study is focussed on S. aureus. Successive pressurization and depressurization cycles appeared to be more efficient than a continuous high-pressure treatment. Importantly, these pressure conditions, temperature and process duration are perfectly compatible with current industrial plants. These results show that HHP technology is a new alternative to inactivate pathogenic strains in accordance with pharmaceutical requirements.     

X‐ray reflectivity measurements of liquid/solid interfaces under high hydrostatic pressure conditions

A high‐pressure cell for in situ X‐ray reflectivity measurements of liquid/solid interfaces at hydrostatic pressures up to 500 MPa (5 kbar), a pressure regime that is particularly important for the study of protein unfolding, is presented. The original set‐up of this hydrostatic high‐pressure cell is discussed and its unique properties are demonstrated by the investigation of pressure‐induced adsorption of the protein lysozyme onto hydrophobic silicon wafers. The presented results emphasize the enormous potential of X‐ray reflectivity studies under high hydrostatic pressure conditions for the in situ investigation of adsorption phenomena in biological systems.     

Decrease in optical density as a results of germination of Alicyclobacillus acidoterrestris spores under high hydrostatic pressure

Alicyclobacillus acidoterrestris is a spore-forming bacterium, causing spoilage of juices. The spores of these bacteria have the ability to survive in the typical conditions used for thermal pasteurization. Therefore, the use of other techniques such as high hydrostatic pressure is considered for their inactivation. The effect of hydrostatic pressure of 200–500 MPa, at temperatures 4–50 °C for 15 min, on the dynamics of germination of A. acidoterrestris spores in apple juice and pH 4 buffer was studied. To estimate the share of germinated spores, the method of determining the optical density at a wavelength of 660 nm (OD₆₆₀) was used. Parameters of hydrostatic pressure treatment used in this work affected the dynamics of germination of A. acidoterrestris spores in apple juice, and the temperature had the greatest effect. The results indicate that nutrients present in apple juice can promote the germination of A. acidoterrestris spores.     

Effect of high hydrostatic pressure on enzyme activity in unpasteurized draft sake

ABSTRACT

Unpasteurized draft sake has a potentially high market value, due to its fresh flavor and fruity taste, compared with conventional thermal-pasteurized sake. However, the shelf life of draft sake is limited. To increase the shelf life of draft sake, it is necessary to suppress flavor and taste deterioration resulting from inactivation of enzymes produced by koji-mold. Draft sake was treated with high hydrostatic pressure (HHP) of 200 to 500?MPa at ?7 to 50°C to analyze the inactivation of α-amylases, glucose-forming enzymes, and acid carboxypeptidases. We found significant inactivation of enzymes produced by koji-mold in draft sake subjected to HHP treatment at both high and low temperature. However, HHP treatment at low temperature effectively inactivated enzymes while retaining the fresh flavor and fruity taste of draft sake.     

Structural and kinetic aspects of hydrostatic pressure effect on polymer network formation

Abstract

Effect of hydrostatic pressure up to 250 MPa on structurization kinetics and morphology of network polymers based on epoxy oligomers has been studied using the methods of measurements of volume resistivity and optical microscopy.     

Evaluation of quality changes of beetroot juice after high hydrostatic pressure processing

ABSTRACT

Freshly squeezed commercially available beetroot juice, a popular beverage in Poland, is a good source of betalains, but as a root vegetable can contain undesirable microflora from the soil. The objective of this study was to investigate the effect of new preservation technique, high hydrostatic pressure, on the beetroot juice quality. Samples of beetroot juice were treated with pressure 300, 400 and 500?MPa/20°C/up to 10 min. Reduction in the total count of spoilage microorganisms reached 3.8, 4.1 and 4.5 log cfu/mL, depending on the pressure. After this treatment beetroot juice showed a 11.3–12.2% decrease in betacyanins content and 7.7–8.9% in betaxanthins content. A significant reduction of the number of spoilage microorganisms with a slight degradation of pigments indicates the possibility of industrial application of high pressure to the preservation of beetroot juice.     

Comparison of microbiological loads and physicochemical properties of raw milk treated with single-/multiple-cycle high hydrostatic pressure and ultraviolet-C light

The effects of ultraviolet-C radiation (UV-C, 11.8?W/m²), single-cycle and multiple-cycle high hydrostatic pressure (HHP at 200, 400 or 600?MPa) on microbial load and physicochemical quality of raw milk were evaluated. Reductions of aerobic plate count (APC) and coliform count (CC) by HHP were more than 99.9% and 98.7%, respectively. Inactivation efficiency of microorganisms increased with pressure level. At the same pressure level, two-cycle treatments caused lower APC, but did not show CC differences compared with single-cycle treatments. Reductions of APC and CC by UV-C were somewhere between 200?MPa and 400/600?MPa. Both HHP and UV-C significantly decreased lightness and increased pH, but did not change soluble solids content and thiobarbituric acid-reactive substances’ values. Two 2.5?min cycles of HHP at 600?MPa caused minimum APC and CC, and maximum conductivity. Compared with HHP, UV-C markedly increased protein oxidation and reduced darkening.     

Effect of high hydrostatic pressure on the profile of proteins extracted from Betula pendula pollens

High hydrostatic pressure (HHP) has high success potential in pollen protein extraction, but its effect on pollen protein profiles has not been studied yet. The aim of this study is to put forward whether HHP processing causes a change in the protein profiles extracted from pollens or not. In this study, proteins extracted from Betula pendula pollens were studied at 100, 200 and 300?MPa at room temperature for 5?min. In addition, the efficiency of three different extraction solvents, namely phosphate buffer saline (PBS) buffer pH 7.5, trichloroacetic acid–acetone and Tris–HCl buffer pH 8.8, was also observed, and the results were compared with the conventional pollen protein extraction procedure. As a result, it is concluded that 200?MPa for 5?min has extracted similar amounts of protein compared with the conventional extraction method which lasted for 24?h, which lasted for 24 h. On the other hand, the application time for 200 MPa for 5 min is extremely shorter when it is compared to the conventional extraction method.     

The usage of high hydrostatic pressure (HHP) to control food-borne pathogens in hummus

ABSTRACT

With the increasing demand for fresher, higher quality, minimally processed and safer food, there is a strong necessity to develop non-thermal processing techniques. Also for hummus, which is popular all around the world. In this work, the effect of refrigerated storage on the survival of pathogens in hummus treated by high hydrostatic pressure (HHP) (500?MPa/10?min/room temperature) was evaluated. The cocktail of two Salmonella, four Listeria monocytogenes and two Escherichia coli strains was used in this study. All pathogen types were able to survive in hummus during 60 days of refrigerated storage. HHP-treated samples plated on day 0 successfully achieved a?>?5 log cfu/g reduction for all pathogen types. No residual survivors were present after 30 and 60 days in any of the HHP-treated samples. These results demonstrate that HHP may be a useful technique for the inactivation of pathogens and therefore helpful in designing non-thermal HHP conditions for pressurization of hummus.     

The effect of high hydrostatic pressure on the physiological and biochemical properties of pepper (Capsicum annuum L.) seedlings

High hydrostatic pressure is a non-thermal food processing technology, which also has several successful applications in different areas besides food processing. In this study, Capsicum annuum L. (pepper) seeds are subjected to 50, 100, 200 and 300?MPa pressure for 5?min at 25°C and the seedlings of HHP processed seeds are used to compare percentage of seed germination and biochemical properties such as chlorophyll a, b and a/b, proline content, total protein, carotenoid, malondialdehyde, glucose, fructose and phenolic compounds concentrations. As a result of the study, it was observed that there are remarkable changes in terms of biochemical properties especially for seedlings, whose seeds were pressurized at 200 and 300?MPa. More detailed studies are needed to put forward the mechanism behind the changes in biochemical properties.     

Listeria monocytogenes cells injured by high hydrostatic pressure and their recovery in nutrient-rich or -free medium during cold storage

ABSTRACT

Cells of Listeria monocytogenes suspended in phosphate-buffered saline (PBS) were treated by high hydrostatic pressure (HHP; 500?MPa, 25°C, 10?min), diluted by ten folds using trypticase soy broth (TSB) or PBS, and stored at cold temperatures of 0–15°C. Viable cell count in TSB increased logarithmically close to the initial count at each storage temperature, while that in PBS increased temporarily and subsequently decreased to almost nondetectable level except the case at 15°C, where it showed logarithmic increase thereafter. Based on proliferation experiments where their healthy cells were inoculated to TSB or to PBS containing their heat-killed dead cells, it was suggested that increase in the viable count of HHP-treated cells in TSB and PBS could be ascribed to the recovery of colony forming ability and/or proliferation depending on the cold storage temperature.     

Depletion of arginine in yeast cells decreases the resistance to hydrostatic pressure

High hydrostatic pressure (HP) inhibits growth and inactivates microorganisms by destabilizing non-covalent molecular interactions. Arginine contributes to stress resistance because it has a guanidine side chain, which assists in the refolding of aggregated proteins. We attempted to analyze the contribution of arginine to high HP stress using a pressure-sensitive mutant strain of Saccharomyces cerevisiae and a metabolomics approach. Our results showed that the content of 136 out of 250 detected metabolites differed in the mutant and parent strains. Decreased metabolites were involved in the tricarboxylic acid cycle and arginine biosynthesis. The expression of genes contributing to arginine biosynthesis was significantly lower in the mutant strain than in the parent strain. When arginine was supplemented to the medium, the mutant strain showed more tolerance to pressure. These results suggest that yeast cells survived due to the contribution of arginine to high pressure resistance. This indicates that depletion of arginine caused by decreased activity of the biosynthesis pathway confers sensitivity to HP.     

Evaluation of high hydrostatic pressure effects on bovine red blood cells and platelets

The objective of this study was to investigate the effects of high hydrostatic pressure (HHP) on the stability of red blood cells (RBCs) and platelets. Bovine blood cells (n=5) were treated with the pressure of 55, 110, 154 and 220 MPa at 25 °C for 5 min. Light microscopy, atomic force microscopy and flow cytometry studies revealed that RBCs were morphologically stable up until the 220 MPa pressure treatments, at which surface modifications were observed. The platelets were found to be less stable than RBCs. HHP application did not cause any significant change in the signal intensity, band area and frequency values of the infrared bands with the exception that a significant variation was observed in the area of the cholesterol band. No statistically significant variations were observed in the secondary structure elements due to HHP treatment according to the artificial neural network study based on the FTIR data.