Initial pH influences in-batch hydrogen production from scotta permeate

We studied the influence of initial pH on hydrogen (H₂) production using permeate from scotta (a partially deproteinized cheese whey from ricotta production) as substrate (51 g L^?1 lactose). Dark fermentation was carried out at 35 °C in laboratory batch reactors, in an unbuffered system. Hydrogen production and metabolite (volatile fatty acids, ethanol, and lactic acid) evolution during a 96-h period were monitored in reactors with initial pH varying in the range 4–10. In all reactors, H₂ production started only when pH fell below 6. However, it was much higher (+31%) in the reactors with initial alkaline pH. We conclude that H₂ production occurs only at acidic pH values, but initial alkaline pH values increase the overall H₂ production in dark fermentation of lactose-rich substrates.     

壳聚糖和茶多酚对鸡肉的保鲜效果及复合保鲜条件的优选

通过测定冷藏过程中鸡肉的细菌总数、挥发性盐基氮(TVB-N)含量、pH值及感官品质,分别研究了壳聚糖及茶多酚对鸡肉冷鲜效果的影响,并结合臭氧浸洗及添加L-抗坏血酸(VC)实现增效,优化出鸡肉复合保鲜处理最优条件:鸡肉经臭氧浓度8 mg/L浸泡清洗20 min,而后浸涂于含有1.5%壳聚糖、0.3%茶多酚及0.5%Vc的复合保鲜液中,可使鸡肉的冷鲜期延长至28 d,保鲜效果明显。     

红茶菌研究进展

红茶菌作为一种传统的民间发酵饮料,因其具有的特殊风味和功效而深受消费者喜爱.红茶菌发酵过程中微生物群落组成、演替和功能代谢对红茶菌生物活性和品质有着重要的影响.本文对近年来红茶菌微生物组成、代谢产物和化学物质组成,以及红茶菌发酵主要影响因素的研究概况进行了综述,以期为研究红茶菌微生物代谢途径、生物活性和发酵工艺的相互关...     

Effects of enzymatic action on the formation of theabrownin during solid state fermentation of Pu-erh tea

BACKGROUND: Theabrownin (TB) is a main bioactive component in Pu‐erh tea, and the total amount is between 100 and 140 g kg^?1. However, reports on the mechanism of formation of TB are sparse because it has a high molecular weight and complex composition. Hence, the mechanism of formation of TB in Pu‐erh tea during solid state fermentation was investigated using an exogenous enzyme method. RESULTS: It was found that, in the presence of exogenous enzymes, the tea liquor prepared from the resulting leaves changed considerably in colour. In addition, the TB, total carbohydrate, polysaccharide, amino acid and protein contents were all increased, while the tea polyphenol content decreased sharply; the surfaces of leaves before fermentation appeared to be smooth and intact, and the structures of the cell, cellulose and lignin were complete, while after fermentation their surfaces were covered by microorganisms and the structures of the cells were largely disrupted. CONCLUSION: The enzymatic actions are closely related to the compositional changes occurring during Pu‐erh tea manufacture, and its quality. Enzymes produced by microorganisms were found to be the main cause of TB formation during the fermentation of Pu‐erh tea. Copyright © 2011 Society of Chemical Industry     

速溶奶茶的研究进展及前景

综述了近几年来速溶奶茶的主要生产技术研究进展,包括水处理、浸提、过滤、净化、浓缩、调配、乳化稳定、均质、干燥、包装等,以及速溶奶茶的市场前景。     

茶水中微量铅的测定

采用阳极溶出伏安法测定茶水中的铅含量,并对测定条件进行优化。结果表明以醋酸-醋酸钠为支持电解质,铅的溶出峰电位为-0.536 V,线性范围为10μg/L~380μg/L,线性方程为Ip=0.238 1c-1.038 9(r=0.999 0),检出限为2.52μg/L。以该方法测定样品的相对标准偏差小于3%,回收率达到92.5%~104.2%。     

Investigation of the Aroma Profile of Green Tea Leaves Using Organic Synthesis and Conventional Analytical Techniques

Although many aroma components have been identified in green tea leaves, the aroma compounds contributing to green tea＇s characteristic odor have not yet been reported. The authors recently reported that aroma components with a matcha-like odor are present in both green tea and black tea prepared from the Sayamakaori tea cuttivar. This matcha-like odor is similar to the odor of commercial available matcha （high-quality powdered green tea）, and is a specific odor feature of green tea leaves. At present, the green-tea odor is thought to arise from the combination of a large number of constituents. Recent reports indicate that a complex interaction between olfactory receptors and odorants is important for the evaluation of the odors. Taking into consideration these findings, the authors investigated the aroma profile of green tea, focusing on the characteristic molecular structures of the constituents that give matcha-like odor. Using a combination of organic synthesis and gas chromatography-mass spectrometry plus gas chromatography-olfactometry, the authors identified aroma components with matcha-like odors in five other tea cultivars. This investigation also revealed that several compounds with a formyl group were important constituents of the aroma of green tea leaves, although the odor of each constituent was not individually similar to the tea＇s overall aroma. The authors found for the first time a group of key components that have the matcha-like odor.     

恭城油茶减轻D-半乳糖致小鼠衰老的氧化应激

通过建立D-半乳糖致衰老模型,观察恭城油茶对衰老小鼠氧化应激的影响.KM小鼠随机分成正常组、衰老模型组、Vc组(100 mg/kg)、恭城油茶组(750 mg/kg).检测肝脏和肾脏指数,血清、肝脏和肾脏组织中谷胱甘肽过氧化物酶(GSH-Px)和总超氧化物歧化酶(T-SOD)活性、总抗氧化能力(T-AOC)活力以及丙二...     

三波长分光光度法测定红茶及其饮料中黄酮的含量

采用三波长分光光度法测定红茶及其饮料中黄酮的含量,消除了由于红茶中黄酮光谱吸收峰不对称给定量分析造成的影响,并校正了基于干扰组分(饮料中添加剂)的吸收光谱具有线性吸收产生的基线倾斜。实验结果,回归方程为:DA=-3.221?0-4 0.06735C,相关系数r=0.9992;黄酮的浓度在1000~3000g/mL范围内,分别在波长为l1=470nm、l2=420nm、l3=370nm处测吸光度时,则DA与浓度C之间呈良好的线性关系,可按标准曲线法进行定量分析。本法的回收率为96.0%~107.0%,变异系数小于0.48%。方法的准确度与精密度均令人满意,而且操作简便易行。     

新型功能性天然色素-茶色素

茶色素是茶叶中提取得到的一种天然色素,具有清除自由基和抗氧化作用,防癌抗癌、防紫外线照射、抗动脉粥样硬化、抗龋护齿等多种药理功能。本文综述了茶色素的生理功能、制备及应用方面的研究进展。