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.     

高温高压下方解石相转变的拉曼光谱原位实验研究

用热液金刚石压腔装置结合拉曼光谱技术研究了高温高压下方解石的相变过程及拉曼光谱特征。结果表明:常温条件下,体系压力增至1 666和2 127 MPa时,方解石的拉曼特征峰155cm-1消失,1 087cm-1峰分裂为1 083和1 090cm-1两个谱峰、282cm-1峰突然降至231cm-1,证明其转变为方解石-Ⅱ和方解石-Ⅲ。在起始压力为2 761MPa和低于171℃的升温过程中,方解石-Ⅲ的拉曼散射的各个特征振动峰没有变化。当温度达到171℃,方解石晶体完全变成不透明状,其对称伸缩振动峰1 087cm-1、面内弯曲振动峰713cm-1和晶格振动峰155和282cm-1均发生突变,说明方解石-Ⅲ相变生成一种碳酸钙新相。体系降至常温,该新相一直保持稳定不变,表明高温高压下方解石向碳酸钙新相的转变过程是不可逆的。方解石-Ⅲ与碳酸钙新相之间的相变线方程为P(MPa)=9.09.T(℃)+1 880。碳酸钙新相的对称伸缩振动峰(ν1 087)随压力、温度的变化率分别为dν/dP=5.1(cm-1.GPa-1),dν/dT=-0.055 3(cm-1.℃-1)。     

Compact multianvil device for in situ studies at high pressures and temperatures

We describe a recently developed device for in situ studies at pressures up to 25 GPa and temperatures up to 2300 K. The system consists of a 450 ton V7 Paris-Edinburgh press combined with a Stony Brook ‘T-cup’ multianvil stage. Such a compact large-volume set-up has a total mass of 100 kg only and can be readily used on most synchrotron radiation facilities. The optimization of the set-up by off-line tests is detailed, and we present some X-ray diffraction results which demonstrate the potential of the technique.     

Raman studies of the high pressure effects in high Tc superconductors

Abstract

The effect of a hydrostatic pressure (up to 6GPa) on the Raman spectra of YBa₂Cu₃O_x(x = 6.5 and overdoped) single crystals is investigated in the temperature range 77-300 K in connection with all available data in the literature for the other oxygen concentrations. All five strong modes (4A_g+1B_1g) are examined for both oxygen doping and compared with previously published results. From the systematic investigation of the phonon spectral characteristics with the application of pressure, the formation or disappearance of the phases is examined. The results provide a spectroscopic support for the changes induced by the hydrostatic pressure on the chain ordering and the corresponding phases.     

High-throughput screening of food additives with synergistic effects on high hydrostatic pressure inactivation of budding yeast

ABSTRACT

We focused on food additives that enhance the effect of high hydrostatic pressure (HHP) treatment for microbial inactivation. We previously isolated Saccharomyces cerevisiae ultraviolet (UV) mutant strain a1210H12 that does not cause a growth delay under specific high pressure treatment conditions. We conceived that it is possible to screen effective food additives in a high-throughput manner by combining strain a1210H12 with a viable cell count method based on liquid culture, named high-throughput microbial pressure inactivation kinetics analysis system (HT-PIKAS). Here, we analyzed the synergistic effect between food additives and HHP treatment on inactivation of strain a1210H12 using HT-PIKAS. We calculated the inactivation rate in the condition of additive only, HHP treatment only and HHP treatment with additive. As a result, four compounds, benzoic acid, sorbic acid, adipic acid and caproic acid, showed high synergistic effects with HHP treatment and could be selected from more than 30 compounds as safe food additives.     

高压下的同步辐射能量色散粉末衍射

 同步辐射已经成为高压研究的一个非常理想的光源。在北京同步辐射装置（BSRF）上、结合金刚石对顶砧超高压实验技术建立起来的能量色散X射线粉末衍射系统,已用于物质状态方程和结构相变的研究。介绍了能量色散衍射方法,以及同步辐射原位测试过程。     

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.     

Possibility of Campylobacter jejuni inactivation in smoked salmon by high-pressure treatment

The sterile samples of cold-smoked salmon were placed in polyamide–polyethylene pouches and inoculated with three-strain composite of Campylobacter jejuni (inoculum ca 10⁷ CFU g^?1). The inoculated samples were sealed under vacuum and subjected to 200, 300 and 400 MPa of hydrostatic pressure for 0, 5, 10 and 15 min. The number of surviving C. jejuni per gram was determined by the 10-fold dilution method followed by plating on Karmali agar. D ₁₀ values were calculated. This work has shown that for reducing C. jejuni in cold-smoked salmon by 6 log units, the application of 200 MPa for 64.26 min or 300 MPa for 17.10 min or 400 MPa for less than 5 min is needed. Applying such parameters of high-pressure processing should not change significantly the organoleptic properties of the product.     

High pressure inactivation of relevant target microorganisms in poultry meat products and the evaluation of pressure-induced protein denaturation of marinated poultry under different high pressure treatments

In this study, the possibility of extending shelf life of marinated poultry meat products by high pressure processing was evaluated. Relevant spoilage and pathogenic strains were selected and used as target microorganisms (MOs) for challenge experiments. Meat and brine were inoculated with MOs and treated at 450 MPa, 4 °C for 3 min. The results of inactivation show a decreasing pressure tolerance in the series Lactobacillus > Arcobacter > Carnobacterium > Bacillus cereus > Brochothrix thermosphacta > Listeria monocytogenes. Leuconostoc gelidum exhibited the highest pressure tolerance in meat. A protective effect of poultry meat was found for L. sakei and L. gelidum. In parallel, the influence of different marinade formulations (pH, carbonates, citrates) on protein structure changes during a pressure treatment was investigated. Addition of sodium carbonate shows a protection against denaturation of myofibrillar proteins and provides a maximum water-holding capacity. Caustic marinades allowed a higher retention of product characteristics than low-pH marinades.     

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.     

The Raman spectroscopic studies of aligned MWCNTs treated under high pressure and high temperature

The study of the aligned multiwalled carbon nanotubes (MWCNTs) for interlinking bonding under high pressures and temperatures have been conducted in the diamond anvil cell. The MWCNT samples were analyzed using the Raman spectroscopy, when treated under the combinations of pressure and temperature ranges of 2-20 GPa and 25-500 °C. The analyses show the formation of interlinking bonding at a pressure above 2.5 GPa when treated under the temperature 500 °C, based on the significant change of the relative intensity between D- and G-bands in the Raman spectra. Comparisons of the data obtained before and after the high pressure and high temperature treatments are reported. The result indicates that the aligned MWCNTs may be easier to form the interlinking bonding compared to randomly oriented MWCNTs.     

Theoretical studies on the high pressure phases of Lanthanum monochalcogenides

We report total energy and electronic structure calculations for lanthanum monochalcogenides in B1 (NaCl) and B2 (CsCl) crystal structures over a range of unit cell volumes. We employed the tight binding linear muffin-tin orbital approach to density functional theory within the local density approximation to expand the crystal orbitals and periodic electron density. In agreement with the experiment we find that B1 phase is lower in energy than B2 phase, and that the compounds transforms to B2 structure under applied pressure. This is the first qualitative prediction of the transition in La monochalcogenides and should be testable with diamond-anvil technique.     

Food safety issues of high pressure processed fruit/vegetable juices

The food safety issues of the high pressure pasteurized fruit/vegetable juices are the focus of this paper. The development of Hazard analysis and critical control points system for production of carrot, red beet and apple/broccoli/orange juice is given together with results of analysis of samples, challenge testing and storage tests. The anti-mutagenic activity in vitro tests are also presented. Procedures have been established for the start-up of experimental production of mentioned juices for the Czech food market. The development of other types of juices based on cruciferous vegetables is mentioned. The aim of this work is to provide the Czech population with information on functional foods that act against chemical mutagens, limiting carcinogenesis.     

Properties of high pressure arc plasma

High pressure argon arc discharges are investigated in the pressure range up to 1000 atm. Experimental values of radiative properties such as the frequency-dependent emission coefficient and the total radiation source strength are compared with theoretical predictions. Solutions of the energy balance of wall stabilized high pressure arcs are presented, the agreement with measurements is good. A comparison of measured electrical conductivities of non-ideal argon plasmas with order measurements and with computations following different theoretical approaches, confirms the poor agreement between theory and experiment found by other authors for this regime. Auszug aus einer Habilitationsschrift am Fachbereich für Elektrotechnik der TU München.     

On convection phenomena during high pressure treatment of liquid media

In the current contribution, investigations of the high hydrostatic pressure process up to 400 MPa and temperatures up to 353 K are carried out by means of dimensional analysis. The thermofluiddynamical mechanisms are analysed for three different sizes of a high pressure chamber, two different pressure generation systems and two model-fluids that differ in viscosity. Forced convection during compression/decompression and free convection during constant pressure phase are considered separately. The results contain process parameter study based on dimensionless numbers derived from conservation equations of mass, momentum and energy. Either dimensionless process parameters or the fluid dynamical and thermodynamical time scales are presented as a function of pressure and temperature. Relations according to heat transfer and fluid flow mechanisms during high pressure treatment are discussed.     

Effect of high hydrostatic pressure processing and squeezing pressure on some quality properties of pomegranate juice against thermal treatment

The aim of this study was to investigate the effect of high hydrostatic pressure (HHP) treatment (200, 300, 400?MPa; 5°C, 15°C and 25°C; 5 and 10 min) on some quality properties of pomegranate juice. Juice samples are obtained under industrial conditions at two different squeezing pressure levels (100 and 150?psi – 0.689 and 1.033?MPa, respectively). Results are compared against conventional thermal treatment (85°C/10 min) and raw sample. For all three processing temperature, HHP combinations at 400?MPa for 10 min were sufficient to decrease the microbial load around 4.0 log cycles for both squeeze levels. All HHP treatments showed no significant decrease at antioxidant activity, total phenolic content and monomeric anthocyanin pigment concentrations, while there was a significant decrease (p?≤?.05) in thermal-treated samples. Being the highest sugar alcohol in pomegranate juice, mannitol content must be considered for determining the authenticity, and mannitol content increased with squeezing pressure and thermal treatment.     

Spectroscopy of II–VI nanocrystals at high pressure and high temperature

We review experimental measurements of CdS, CdSe, and CdS_xSe_{1 − x} nanocrystals which address the properties and phase stability of both powder and embedded nanoparticles under extreme conditions. We address the high pressure phase transition of wurtzite or zincblende phase to the rock salt structure; the high temperature solid to liquid phase transition; and the homogeneous nucleation of nanoparticles in glass from dissolved reactants. We also review the use of high pressure optical measurements to study electronic states.     

Effect of high pressure processing on the preservation of frozen and re-thawed sliced cod (Gadus morhua) and salmon (Salmo salar) fillets

Cod and salmon are both widely found in the seafood market, but those products are easily spoiled. This work reports on the investigation of the effects of three moderate pressure values (150, 300 and 450?MPa) applied for 5?min at 20°C on crude sliced cod and salmon fillets. It was found that high pressure processing (HPP) significantly reduced the microbial load during refrigerated storage for up to 14 days. As expected, the most effective treatment was 450?MPa because it inhibited microbial growth. This process affected the hardness, lightness, lipid oxidation, protein denaturation and oxidation. The fish muscle composition (lipid amount and protein profile) played a main role in the changes promoted by pressure. HPP permits the shelf life of the raw product at 4°C to be increased with minimal changes in the organoleptic characteristics and to enable crude consumption.