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1.
ABSTRACTHigh 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. 相似文献
2.
Raman spectra of a crystal of L ‐leucine, an essential amino acid, were obtained for pressures between 0 and 6 GPa. The results show anomalies at three pressure values, one between 0 and 0.46 GPa, another between 0.8 and 1.46 GPa, and a third at P ∼ 3.6 GPa. The first two anomalies are characterized by the disappearance of lattice modes (which can indicate occurrence of phase transitions), the appearance of several internal modes, or the splitting of modes of high wavenumbers. The changes of internal modes are related to CH and CH 3 unit motions as well as hydrogen bonds, as can be inferred from the behavior of bands associated with CO 2− moieties. The third anomaly is a discrete change of the slopes of the wavenumber versus pressure plots for most modes observed. Further, decompression to ambient pressure generates the original Raman spectrum, showing that the pressure‐induced anomalies undergone by L ‐leucine crystals are reversible. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
Raman spectra of an L ‐methionine (C 5H 11NO 2S) crystal were obtained in the spectral region between 50 and 3200 cm −1 for pressures up to 5 GPa. Pronounced changes of the Raman spectra were observed for bands associated to rocking of CO 2−; wagging of CO 2−; deformations of CO 2−, CH 3, and NH 3+; and stretching vibrations of SC, CC, CH, CH 2, and CH 3. Upon decompression to ambient pressure the original Raman spectrum prior to compression is recovered. These modifications were associated to a reversible phase transition undergone by the L ‐methionine crystal at about 2.2 GPa, with a hysteresis of ∼0.8 GPa. Pressure coefficients for most of the internal modes of the crystal are given. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
详细介绍了温压结合超高压杀菌技术的优点,指出其独特的应用优势,深入完整地综述了温压结合超高压处理对各类细菌芽孢的杀灭作用及动力学研究成果,并对温压结合超高压处理杀灭芽孢的机理做了初步总结。在此基础上,分析了该研究领域尚存在的问题,提出了未来的研究重点和方向。 相似文献
5.
以78 MPa高静水压力处理已浸泡10 h的水稻(Oryza sativa L.)粤香占、粤丰占和测64种子12 h,成苗后移栽至大田,对其处理当代和后代的农艺性状进行调查和分析,结果表明,处理当代中,粤香占、粤丰占和测64的穗粒数分别增加了5.2%、1.2%和17.0%,且测64达到显著性差异水平;测64处理的生育期延长10 d,而粤香占和粤丰占则分别早熟5 d和2 d 。在处理的当代和后代中出现了可遗传的突变体,突变性状中既有质量性状也有数量性状,其中紫色叶鞘和穗下节伸长属于质量性状突变,株高、粒长和穗粒数等属于数量性状突变。突变频率因品种不同而存在差异,表现为:测64粤丰占粤香占。通过4年6代的筛选,共获得近100份包括叶、茎、穗、粒、育性和生育期等性状发生明显变异的突变体,已稳定的突变株系22个,其中7个突变株系的综合性状明显较对照好,具有良好的应用前景。 相似文献
6.
利用不同静水压力和不同保压时间处理了籼稻粤香占种子,研究发现,随着压力的增加和保压时间的延长,水稻发芽率和成苗率明显下降,高压处理后的水稻在苗期的生长受到明显抑制,大约生长30 d株高才赶上对照;聚丙烯酰胺凝胶电泳显示高静水压力抑制了种子幼苗的酯酶(Esterase)同工酶的表达,但对其它几种同工酶如过氧化物酶(Peroxidase)、超氧化物歧化酶(Superoxider Dismutase)和苹果酸酶(Malic Enyme)等影响较小。利用同一压力和保压时间处理,不同类型的水稻(Oryza sativa L.)品种种子,其中包括籼稻(粤香占和南京11)、粳稻(秋光和台中65)和中间类型Bulu稻(Bulu Gendjah 和Bulu Rusa),结果发现所有类型水稻种子的发芽率和成苗率都显著降低,但因水稻类型的不同其影响程度也不同,籼型水稻南京11和粤香占的耐压性最弱,粳型水稻秋光和台中65最强,中间型Bulu水稻Bulu Gendjah和 Bulu Rusa居中。上述结果表明,静水高压能够显著降低水稻的种子的发芽率和成苗率,抑制幼苗前期的生长和酯酶同工酶的表达。 相似文献
7.
应用流体静压法制备YBaCuO体系大型高T c超导棒材。样品尺寸为Φ11 mm×115 mm,其中外形规正,密度均匀。超导转变参数为:起始转变温度为105~106 K,零电阻温度为89~92 K,中点转变温度为92~93 K,转变宽度为5 K左右。 相似文献
8.
研究了高静压/热处理对不同品种黄桃罐头质构的影响。实验结果表明,不同品种特性对高静压加工黄桃罐头果肉的硬度和汤汁黏度无显著影响,热处理使黄桃罐头果肉硬度显著下降,汤汁黏度显著上升,“森克林”品种黄桃罐头在高静压/热处理后硬度最高,质构最好。显微结构分析显示,不同品种特性对高静压加工黄桃罐头果肉细胞的形态无显著影响,细胞基本保持原有形态;热处理使果肉细胞的形态发生了较大的变化,细胞变形且呈无规则形状,细胞间隙明显增大。高静压能使黄桃罐头保持良好的质构,品种适应性较热处理广泛。 相似文献
9.
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. 相似文献
10.
综述了高静压对淀粉的影响。阐述了高静压的定义及其原理,与高静压的作用直接相关的淀粉结构及其性质。根据文献资料报道对25种以上淀粉的研究表明,高静压不仅对淀粉结构影响明显,包括微观结构、宏观颗粒形态,而且对淀粉糊化过程及性质也有较大的影响。施加的压力、淀粉的种类、处理温度、溶液浓度不同,对淀粉的结构和糊化影响也显著不同。大量的研究表明,高静压对淀粉的处理是有潜力的非热物理变性的手段,通过利用不同的高静压处理手段,得到不同品质的高静压淀粉产品,使淀粉在不同的领域中发挥更大的作用。 相似文献
11.
对经高静水压处理的水稻粤香占(Oryza sativa L. cv. Yuexiangzhan)种子播种后的植株进行了抗氧化酶活性的测定和对逆境胁迫响应的研究。结果表明,高压处理抑制了水稻生长早期(12 d)色素和蛋白质含量的增加,并使早期抗氧化酶活性表现较对照低。随着播种天数增加,经高压处理的材料中的色素、蛋白质含量不同程度地增加,抗氧化酶活性发生改变,至播种后32 d时,高压处理的叶绿素含量和可溶性蛋白含量都高于对照粤香占。在自然低温条件下,经高压(干压、湿压)处理的植株其Rubisco大、小亚基含量和光合色素含量较高,抗光抑制能力增强,具一定的耐低温性。 相似文献
12.
实验研究了皱纹盘鲍的超高压脱壳工艺,评价了超高压脱壳对鲍鱼品质的影响。结果表明:超高压处理有利于鲍鱼的脱壳,200 MPa保压1 min和300 MPa不保压的超高压处理组与对照组(手工脱壳)相比,脱壳时间分别节约69%和72%,同时提高了鲍鱼的完整性,鲍鱼肉得率分别提高18%和16%;超高压脱壳处理后,鲍鱼菌落总数从2.2×103 cfu/g减少至270~350 cfu/g,水分含量显著增大,pH值变化不显著(P > 0.05);经超高压脱壳后,鲍鱼肉的亮度L显著增大,而红度a和黄度b较对照组降低,有效改善了鲍鱼的色泽;随着处理压强的增大和保压时间的延长,鲍鱼硬度增加,弹性下降。经综合评价,选择处理压强300 MPa、保压时间为零作为最佳超高压脱壳工艺参数。 相似文献
13.
以75 MPa静水高压处理萌动的水稻种子12 h,成苗后移栽至大田,研究高压处理后植株剑叶光合特性的变化。结果显示,静水高压处理后,粤香占和粤丰占种子的发芽率分别降低了14.4% 和16.6%,成苗率分别降至对照的24.6%和21.9%,生长明显受抑制,幼苗的株高在35天左右才能追赶上对照。高压处理的粤香占剑叶在生育过程中的净光合速率(Pn)和表观量子效率(AQY)的总平均值分别比未处理的对照增加了9.2%和12.4%,而粤丰占则分别增加5.7%和17.4%。高压处理后两个品种的植株叶片不同生长时期的平均光合色素含量均高于未处理的对照,在生长后期的衰老过程中高压处理植株剑叶的色素含量和PSⅡ光化学效率Fv/Fm下降速率较各自的未处理对照缓慢。高压处理后两个水稻品种的生物量和单株产量分别比对照提高了8%~27%及7%~14%。提出高压处理可能作为一种新的选育品种的方法。 相似文献
14.
In CdGeAs 2<Mn>, a metamagnetic phase transition and a negative magnetic resistance induced by high pressure were found and studied. 相似文献
15.
树莓多酚氧化酶具有较强的耐压性,在600 MPa压力下处理45 min,其残余酶活仍高达40%以上。为了进一步钝化树莓内源多酚氧化酶的活性,研究了金属离子辅助高静压对树莓多酚氧化酶钝化的影响。在树莓多酚氧化酶粗酶液中添加对酶活性有抑制、激活、无改变的金属离子,研究其辅助400、600 MPa压力处理钝化树莓多酚氧化酶的效果。发现添加金属离子后,多酚氧化酶的活性随压力增大、时间延长而降低;Fe2+、Mn2+以及Cu2+均有不同程度的协同高静压钝化作用,而Ca2+在钝化树莓多酚氧化酶时与高静压出现拮抗现象,对树莓多酚氧化酶活性无影响的Zn2+未出现协同/拮抗作用。 相似文献
16.
Abstract The galvanomagnetic properties of electron-irradiated n- and p-InSb under high hydrostatic pressure have been investigated. It has been shown that electron irradiation generates a series of deep levels split from the valence band. 相似文献
17.
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. 相似文献
19.
为探讨不同杀菌方式对胡萝卜汁品质的影响,以鲜榨胡萝卜汁为对象,研究了超高压(600 MPa,5 min)和热杀菌(90 ℃,5 min)处理前、后及其在贮藏过程(4和27 ℃)中的品质变化。结果表明:经热杀菌处理的胡萝卜汁的亮度L、红色值a、黄色值b和总色差ΔE显著上升(P < 0.05),而超高压处理的胡萝卜汁的a值和总色差ΔE显著上升(P < 0.05),但L值和b值却没有显著变化(P > 0.05);贮藏过程中L、a、b值均上升,总色差ΔE下降(P < 0.05)。超高压和热杀菌处理前、后,胡萝卜汁的pH值、可溶性固形物及浊度均没有显著变化;在贮藏过程中,胡萝卜汁的pH值没有显著变化,可溶性固形物呈上升趋势,而浊度呈下降趋势。经过超高压处理后,胡萝卜汁的流变性比热杀菌处理时更接近牛顿流体,并且在贮藏过程中超高压处理的胡萝卜汁的流动特性指数n没有显著变化,而经热杀菌处理的胡萝卜汁的n值则先上升后下降。胡萝卜汁在超高压和热杀菌处理后,抗氧化性均有显著提高(P < 0.05),而α-和β-胡萝卜素含量及颗粒分布的变化不显著(P > 0.05),但是在贮藏过程中胡萝卜素含量逐渐下降,并且有新的颗粒产生。 相似文献
20.
以两个水稻(Oryza sativa L.)品种粤香占和毕粳38号为材料,通过高压处理,获得了5个当代突变体和4个后代分离出的突变体。ISSR分析表明高压可以诱导水稻产生变异,这种变异是由于遗传物质(DNA)的改变所引起的。由高压诱变产生的水稻突变体不仅在当代出现,而且具有很高的遗传稳定性,突变体与原种的遗传差异越大,其稳定性越高。 相似文献
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