外文文献翻译

外文文献翻译

Effects of pulsed electric fields on bioactive components, colour and flavour of green tea infusion

Author :Zhao, Wei ；Yang, Ruijin ；Wang, Mo ；Lu, Rongrong

Abstract: Green tea is an unfermented tea containing a higher quantity of bioactive components. In this paper, the effects of pulsed electric field (PEF) treatments on the bioactive components (polyphenols, catechins and free amino acids), colour and flavour of green tea infusions were studied. PEF as a promising non-thermal sterilisation technology could efficiently retain polyphenols, catechins and original colour of green tea infusions with electric field strength from 20 to 40 kV cm(-1) for 200 mu s. PEF treatments caused a significant increase in the total free amino acids of green tea infusions. The total free amino acids increased by 7.5% after PEF treatment at 40 kV cm(-1). The increase in total amino acids induced by PEF treatment, especially to theanine, is beneficial for the quality of commercial ready-to-drink green tea infusion products. There was no significant effect of PEF treatment at 20 or 30 kV cm(-1) on flavour compounds of green tea infusions. However, PEF treatment caused losses of volatiles in green tea infusions to different extents when PEF dosage was higher than a critical level. The total concentration of volatiles lost was approximately 10% after PEF treatment at 40 kV cm(-1)

for 200 mu s.

Keywords :green tea infusion green tea color green tea flavor

高压脉冲电场对绿茶提取液的生物活性成分、颜色及其香味的影响摘要：绿茶是一类未发酵的茶，内含大量的生物活性成分。本文讲述用高压脉冲电场对绿茶提取液进行处理，来研究其对绿茶生物活性成分(多酚类、儿茶素、游离氨基酸)、绿茶的颜色及香味成分的影响。PEF是一种有发展前景的的非热能的灭菌技术，它能够有效地保留用20到40 kV cm(-1)高压脉冲电场中处理200分钟的绿茶提取液中的多酚类、儿茶素及绿茶色素。PEF处理后的绿茶提取液中的整体的游离氨基酸含量增加。在40 kV cm(-1)高压脉冲电场处理下的游离氨基酸含量增加7.5%，整体氨基酸含量的增加是由于PEF处理导致的，这种处理技术对于提高商业中的绿茶饮料产品中的质量有益，尤其对于茶氨酸。而将绿茶提取液置于20 或30 kV cm(-1)条件下用PEF处理对绿茶香味成分没有什么影响。然而，当用超于临界的剂量的PEF 处理绿茶提取液会使得绿茶提取液挥发物不同程度地减少。经过用PEF在40 kV cm(-1)条件下处理200分钟的绿茶提取液的挥发物大约减少10%

关键词：绿茶提取液：绿茶颜色：绿茶香味

Potentiometric flow-injection estimation of tea fermentation degree

Author :Nieh, CH ；Hsieh, BC ；Chen, PC ；Hsiao, HY ；Cheng, TJ ；Chen, RLC

Abstract: A potentiometric flow-injection (FI) system was developed for estimating tea fermentation degrees; the method is based on the redox potentials or tea infusions. The infusions were extracted with phosphate buffer (10 mM, pH7.0), and injected (200 mu L) into the FI system (1 mLmin(-1)). The redox potentials (vs. Ag/AgCl) of carrier stream were monitored with a home-made electrochemical flow cell equipped with a platinum indicating electrode. Flow-injection strategy Successfully decreased the problem of electrode fouling with increased reproducibility (S.D.<1.5 mV) and elevated sample throughput (>20determination h(-1)). During indoor withering process (0-24 h) for making pouching tea, the redox potential of tea infusions rose (110-130mV) along with the depletion of tea catechins. The system can also be used to estimate the fermentation degrees of commercial tea samples. For commercialization, the platinum electrode can be replaced with a screen-printed carbon-paste disposable electrode with similar performance.

Keywords:potentiometric,flow-injection,tea-fermatationdegree ,Redox-po tential ,Tea-catechins

用电位计流动注射器判断茶叶发酵程度