Colour Changes During Ripening of High Pressure Treated Hard Caprine Cheese

High hydrostatic pressure (HHP) treatment of cheese intended to accelerate ripening. Along with increased proteolysis, some other parameters were affected, colour being one of them. Right after HHP and at the end of ripening time, Hunterlab colour parameters were very similar in both control and cheese treated at 400 MPa, but during ripening they evolved in a different way. HHP-treated cheese had lower lightness and higher chroma values than control cheese and both characteristics were unexpectedly associated to higher moisture values. Those differences are attributed to changes in cheese microstructure.     

High Pressure Effect on Meat and Lupin Protein Digestibility

High pressure treatment is a mild treatment concerning the nutritional characteristics: for instance vitamins content is very few affected by high-pressure treatment. But the impact of high-pressure on protein digestibility remains poorly understood. This work presents effect of high-pressure treatment on in vitro digestibility of meat and lupin proteins. Two high-pressure conditions (200 and 500 MPa 10 min.) and a heat treatment of 95 °C, 30 min were studied. In vitro digestibility was evaluated with a pepsin reaction. Results show than for both type of proteins, samples pressurised at 500 MPa were the most hydrolysed. Meat proteins were less hydrolysed than control either after heat or 200 MPa treatment. Lupin proteins where more hydrolysed than control after heat or 200 MPa treatment. Thus we revealed that high-pressure treatment presents an effect on the in vitro digestibility of proteins, opening a new perspective of investigations.     

高温高压下电解质溶液谱学研究的进展

高温高压下电解质溶液研究在理论和工业应用上都具有重要的意义，拉曼光谱、红外光谱、紫外可见光谱、中子和X射线衍射、以及X射线吸收精细结构方法都已经用于它的研究。随着温度升高，溶液的结构发生了变化，离子的缔合度增加，内层配位水的数目减少，出现了离子的多核簇组成。除了静态结构的研究外，也用拉曼光谱进行溶液的动力学探讨。水热金刚石压腔装置是高温高压电解质溶液研究的一个重要的进步，在水热金刚石压腔装置中，拉曼光谱和X射线吸收精细结构两种方法具有重要的应用潜力。     

Effects of high pressure treatment on the quality of cooked pork ham prepared with different levels of curing ingredients

The aim of this study was to define the effects of high-pressure treatment (600 MPa, 10 min, 20 °C) on the quality of cooked pork ham prepared with two different levels of curing ingredients in brine. Physical, chemical, microbiological, and sensory tests were performed 24 h after high pressure processing (HPP), as well as after 6 and 8 weeks of storage in refrigerator conditions. The results indicate that HPP causes significant improvement of shelf life of vacuum packed ham, including the samples with reduced level of curing ingredients in brine to 8 weeks in refrigerator conditions (4–6 °C). HPP did not have significant effect on the texture or color of ham. However, it significantly increased the drip loss during storage in the packed samples. This may indicate that HPP has negative effects on water holding capacity of cooked products.     

Effect of High Pressure on the Consumer Liking and Preference of Yoghurt

One hundred consumers evaluated three types of set yoghurt made from: 100% pressure treated milk (PTM; 600 MPa for 15 min), 100% heat treated milk (HTM; 85 °C for 20 min) and a mixture containing 10% PTM and 90% HTM. There was no significant difference between appearance liking or texture liking of the three yoghurt types, though the texture score of PTM yoghurt and mixed milk yoghurt were both higher than HTM yoghurt. Creaminess score for PTM yoghurt was significantly higher than for HTM yoghurt; mixed milk yoghurt was significantly different from HTM yoghurt but not from PTM yoghurt. Concerning taste liking, PTM yoghurt scored significantly less than mixed milk yoghurt, with HTM yoghurt between these two. 57% of consumers preferred the HTM to PTM yoghurt, giving taste as their main criteria; those preferring PTM yoghurt based their choice on texture. Rheological assessments showed differences in gel structure, which justify consumer texture and creaminess choices.     

Optical Method for the in-situ Measurement of the pH-value During High Pressure Treatment of Foods

This contribution presents a novel optical method to determine the pH-value during the high pressure treatment of foods. Up to date an appropriate online measurement device does not exist. The present study makes use of a multivariate approach, using the optical properties of pH indicators. An indicator mix of 16 different pH-sensitive substances is applied. The calibration of the system is performed taking five different buffer substances (TRIS, CAPS, citric, phosphoric and acetic acid buffers), applying thermodynamical considerations, to calculate the pH-value at high pressure. The corresponding spectra of the indicator mix is measured and fed to a multivariate data model together with calculated pH values. Different chemometric models have been constructed to estimate the pH value based upon the spectrum of the indicator mix. The calibration device covers a pH range from 2 to 8. After calibration it was possible to determine the pH value at pressures up to 450 MPa with an accuracy of 0.02 pH units in 9 different test media.     

Increasing Preservation Efficiency and Product Quality through Control of Temperature Distributions in High Pressure Applications

The effectiveness of HP sterilisation is a function of both temperature and pressure. As during pressurisation the product temperature increases, heat transfer to the colder HPP vessel wall occurs and the product fraction near the vessel wall will be colder than the product in the middle of the vessel. The effect of the temperature distribution in the vessel on the inactivation of Bacillus stearothermophilus has been examined. A mathematical model has been built, in which both thermodynamics and inactivation kinetics are integrated. Heat transfer is based on a Finite Element simulation, inactivation kinetics are based on first order kinetics. Based on this model and experiments the effect of an homogeneous temperature distribution on inactivation is demonstrated.     

High Pressure Studies on the Optical and Electronic Properties of Para -Terphenyl

Based on X-ray powder diffraction experiments of p -terphenyl that yield pressure dependent lattice parameters, we performed geometry optimizations of all structural degrees of freedom including bond lengths and bond angles as well as molecular orientation using ab initio bandstructure methods. For these optimized structures we calculated the dielectric tensors. Upon increasing pressure we find a spectral red shift of the lowest energy absorption feature that is significantly smaller than that of the second peak at higher energies. We attribute this effect to intermolecular interactions that affect the bands involved in the second transition more than the bands giving raise to the first transition. This picture is confirmed by quantum chemical calculations for single molecules with the internal geometry extracted from the optimized structures.     

Overview: Effect of High Pressure on Enzymes Related to Food Quality - Kinetics as a Basis for Process Engineering

In the last decade, high pressure technology received a major interest in food processing/preservation since it offers some advantages especially in retaining food quality attributes ( i.e. colour, flavour and nutritional value). In the framework of defining HACCP guidelines or 'Novel Food' regulation, and also from an engineering point of view, kinetics of pressure process impact on safety and quality aspects of foods are indispensable. In this context, quantitative kinetic studies of the combined pressure and temperature effect on several food related aspects such as food quality related enzymes, pathogenic/spoilage microorganisms, nutritional and sensorial quality characteristics are required. Moreover, from an engineering point of view, such kinetic data are of major importance for evaluation of process uniformity, for process validation and process optimisation.     

Effects of dielectric barrier discharge plasma on pathogen inactivation and the physicochemical and sensory characteristics of pork loin

This study aimed to evaluate the use of a dielectric barrier discharge (DBD) plasma system to improve the safety of pork loins. When pork loin was exposed to DBD plasma with the input gases He and He + O₂, the population of Escherichia coli was reduced by 0.26 and 0.50 log cycles following a 5-min treatment and by 0.34 and 0.55 log units following a 10-min treatment, respectively. That of Listeria monocytogenes was also reduced from 0.17 to 0.35 and 0.43 to 0.59 log cycles when the samples were exposed to DBD for 5 and 10 min using He and He + O₂, respectively. The pH and L*-values (lightness) of the samples decreased significantly with DBD plasma treatment, but a*- (redness) and b*-values (yellowness) exhibited no obvious changes. Lipid oxidation, measured by TBARS values, was greater in samples with He + O₂ than in other samples. Significant reductions in sensory quality parameters (appearance, color, odor, acceptability, etc.) were observed in DBD-treated samples. These results indicate that the DBD plasma system has potential for use in sanitizing pork loins by inactivation of foodborne pathogens, although the effect was limited. In order to meet market requirements, however, a method to overcome sensory deterioration of pork loins should be developed and applied.     

New Members of the RuSr 2 RECu 2 O 8 Family of Phases (RE=Rare Earth) Obtained at High Pressure and Temperature

At room pressure, Sm, Eu and Gd seem to be the only RE elements that accept to enter into the structure of RuSr 2 GdCu 2 O 8 . However high pressure and high temperatures allow one to replace gadolinium by other lanthanide cations. We have been successful in replacing Gd by Y, La, Pr, Nd, Tb, Dy, Ho and Er. X-ray diffraction patterns fitted by the Rietveld method show that the average crystal structure of RuSr 2 RECu 2 O 8 is tetragonal with P 4/ mmm space group symmetry. Micro-Raman experiments have been performed on RuSr 2 GdCu 2 O 8 samples synthesized at both high and room pressure; the resulting spectra are consistent with the same structure, since there are no major changes in the low-frequency range.     

A New High Pressure - Low Temperature Process for the Synthesis and the Crystal Growth of Gallium Nitride

Gallium nitride can be synthesized by a solvothermal route using ammonia as solvent and a nitriding additive (such as hydrazine hydrochloride NH 2 NH 3 Cl or sodium azide NaN 3 ) encapsulated in melt gallium as chemical reagents. The involved temperature and pressure are respectively 600 °C and 150 MPa. The synthesized products are then characterized by X-Ray Diffraction and Scanning Electron Microscopy. The synthesis parameters influence the powder morphology and purity.     

Relation between the Superconducting Transition Temperature and the Axial Ratio in R Ni 2 B 2 C ( R =Y,Ho, Er,Tm, Lu) Under High Pressure

The effect of pressure on the lattice parameters of R Ni 2 B 2 C ( R = Y, Ho, Er, Tm, Lu) has been measured in order to investigate the relation of T C to axial ratio c/a in the tetragonal lattice or the cohesive properties of these materials. The large anisotropies are observed in the lattice compression curves especially for R =Ho and Tm; the c -axis is more compressible than the a -axis. On the other hand, the anisotropy in the lattice compression is found to be relatively small for R =Y and Lu. The close relation between T C and c/a is pointed out particularly for R =Ho.     

高压热处理对铝青铜热物理性能的影响

在5 GPa压力下对铝青铜进行750℃、保温15 min的高压热处理,对高压热处理前后铝青铜的电导率以及25～600℃温度范围内的热扩散系数、热容和热导率进行测试,结合显微组织的观察结果,探讨了高压热处理对铝青铜热物理性能的影响。研究表明:高压热处理能增大铝青铜的热扩散系数,减小热容;对热导率而言,温度低于400℃时高压热处理能增大铝青铜的热导率,而温度高于400℃时高压热处理能减小铝青铜的热导率。分析认为,产生变化的主要原因是高压热处理使铝青铜的微观组织发生了变化。     

动态瞬时高压作用对膳食纤维酶解速度的影响

 对纤维素酶对动态瞬时高压处理后膳食纤维的酶解速度进行了研究。豆渣膳食纤维（Dietary Fiber,DF）经微射流均质机的瞬时高压作用（Instantaneous High Pressure,IHP）,在不同的压力以及同一压力的不同作用次数下产生不同粒径和密度,它们对应的酶解速度是不同的。纤维素酶水解膳食纤维产生纤维二糖和葡萄糖等还原糖,通过测定水解后还原糖的含量判断不同粒径和密度的膳食纤维的酶解速度。结果表明,在40～90 MPa的压力范围内随压力的增大物料粒径呈显著下降,物料密度随之增大,酶解速度增大,在90 MPa的均质压力下物料粒径达到最小,为202.4 nm;当压力继续增大时,物料因膨化作用,物料粒径呈增大趋势,但其密度开始减小,酶解速度继续增大,在140 MPa的均质压力下物料密度达到最小,为1.027 g/mL,此时酶解后还原糖含量最高,酶解速度最快。压力超过140 MPa后,由于超微颗粒间的团聚,物料的密度和粒径均增大,酶解速度减小。在90 MPa和140 MPa下对分别对物料进行多次的瞬时高压处理,发现随处理次数的增多物料粒径增大,体系密度先减小后增大,酶解速度减小。     

TDLAS波长调制法中调制深度与高次谐波中心幅值关系的研究

可调谐半导体激光光谱技术（TDLAS）是近年来发展十分迅速的光谱检测技术,相较于其他光谱检测技术,它具有高灵敏度、高分辨率、实时监测、便携性好、小型化等优点,在工业环保、医疗检测、气象监测等领域得到了广泛的应用。TDLAS波长调制法中谐波信号易受气压影响,经研究发现气压的影响是调制深度对谐波信号的影响,基于TDLAS技术谐波法的原理,研究了各次谐波与调制深度的关系,通过计算四次谐波与二次谐波中心幅值比,利用调制深度函数推算当前气压环境的调制深度,调整调制频率幅度,使得调制深度接近各次谐波最佳调制深度值,使谐波信号信噪比最佳,提高检测精度。实验通过国瑞智GRZ5031湿度发生器产生固定为1 000 ppm的水汽,调节气阀控制密封箱内不同的气压环境,采用TDLAS水汽检测系统获得了10.2~177.9 kPa气压条件下的二次谐波和四次谐波信号,并进行了仿真与实验分析。仿真结果显示：四次谐波与二次谐波中心幅值比的理论值和仿真值最大相对误差为-1.44%,调制深度的理论值与仿真值最大相对误差为1.78%,说明了仿真下的调制深度函数曲线与理论一致。实验结果显示：根据调制深度函数推算调制深度值,当m=2.226 7时,实测的二次谐波中心频率幅值达到最大值,当m=4.061 0时,实测的四次谐波中心频率幅值达到最大值,与理论结果一致;在30.2 kPa<p<177.9 kPa时,调制深度与气压乘积mp值相对误差较小,最大相对误差不超过±3.2%,说明了此气压条件下的mp值波动不大,通过调制深度函数推算的调制深度值与实际值近似,验证了调制深度函数理论的准确性。     

The Effect of Pressure on Vibrational Spectra of the Chiral Coordination Compound Ni[(R,R)bdtp] 2

The present work deals with the effect of pressure on vibrational spectra of the chiral coordination compound bis-cyclo-O,O'-[1(R),2(R) dimethylethylene] dithiophosphate nickel(II) complex, Ni[(R,R)bdtp] 2 , in short. The analysis of the pressure dependence of FTIR and Raman spectra shows the splitting of some vibrational modes and the appearance of new bands at about 2.5 GPa. These findings are related to a possible pressure-induced molecular or crystal modification, as yet not fully understood, which would affect the symmetry environment of the metal, as well as that of its neighbor dithiophosphate groups.     

高压与加热协同处理对牛肌肉中蛋白酶活性的影响

在不同温度(20～60℃)和压力(0.1～600 MPa)下处理20 min,对牛肌肉中蛋白酶活性的影响进行了研究.结果显示:室温下,随着处理压力的增加,酶的活力显著下降,而压力达400 MPa及以上时,酶的活力则没有明显变化,同时在pH值为3和7.5时酶的活性几乎完全丧失.200 MPa以下的压力处理使肌肉中游离氨基...     

采用FTIR技术研究高压处理对冻干大豆分离蛋白构象的影响

采用傅里叶转换红外光谱技术(FTIR)研究了高压(HP)处理对冷冻干燥的大豆分离蛋白(SPI)构象的影响。在SPI的去卷积FTIR光谱的酰胺Ⅰ′区域(1 600～1 700 cm-1),观察到12个与蛋白构象相关的红外吸收峰,分别对应于CO键伸缩振动与肽键的C—N伸缩振动。通过对该区域的峰强度与波数分析显示,压力为200～400 MPa的HP处理导致SPI在该区域的峰发生明显的“红移”(约2 cm-1),强度也显著增加。更高的HP处理进一步增强了SPI的酰胺Ⅰ′区域的峰强度。对酰胺Ⅱ峰分析显示,HP处理导致酰胺Ⅱ峰(如1 560～1 500 cm-1)的强度、面积逐渐增加(与压力呈正相关)。以上分析显示,HP处理导致SPI的二级与三级结构逐渐打开,然而变性蛋白的结构在高压释放后经历一个“重构过程”。     

高压处理对BiSrCaCu2Oy超导电性的影响

 本文在高T_c超导体BiSrCaCu₂O_y常压制备的基础上，研究了热压烧结和冷压处理对其形成、结构及超导电性的影响，并与常压结果进行了比较。结果表明，高压可以使样品的合成时间缩短，合成温度降低。但同时它也抑制了晶格参数较大的相（高T_c相）的形成，使小晶格参数的杂相含量增多。对于提高样品的超导电性而言，1.5 GPa时一个较好的压力点。