绿茶提取物的功能和发展状况

饮茶有益健康,不仅在中国,现今西方发达国家对茶叶功能成分,也有较多的研究。特别是儿茶素和表没食子儿茶素没食子酸酯(EGCG),普遍认为儿茶素和EGCG具有抗氧化、抑菌、抑制肥胖等功效。作为功能配料和膳食补充剂的绿茶提取物,已大量出口到日夲、德国、法国、美国等国。作者简单介绍了国内外儿茶素及EGCG的发展状况。     

醒发过程中绿茶馒头面团品质变化研究初探

本文主要研究绿茶馒头面团在醒发过程中茶多酚、游离氨基酸和叶绿素以及物性指标的变化规律。实验结果表明,随着醒发时间的增加,面团中功能成分呈递减趋势,面团的硬度、粘聚性、胶着性和咀嚼性越来越小,而粘着性、弹性和回复性越来越大;醒发时间一定的条件下,随绿茶粉添加量的增加,功能成分减少速率呈递减趋势,面团的硬度、粘着性、粘聚性、胶着性及咀嚼性增大,而弹性及回复性逐渐减小。     

Formation and Characterization of Green Tea Extract Loaded Liposomes

Green tea extract was encapsulated into liposomes to enhance bioavailability and stability of catechins by protecting their functional properties simultaneously. Encapsulation was achieved by dispersing 1% (w/v) soy lecithin through high pressure homogenization (microfluidization) and ultrasonication. Effects of homogenization type and pH of the dispersing medium on the physical properties and stability of the liposomes during 1‐mo storage period were investigated. Mean particle size, total phenolic content by Folin–Ciocalteu method and antioxidant activity by 2‐diphenyl‐1‐picrylhydrazyl radical scavenging and ferric reducing‐antioxidant power methods, and transmission electron microscopy (TEM) experiments were conducted for characterization. Green tea extract loaded liposomes prepared by microfluidization in distilled water were determined as the most stable system which demostrated no significant difference (P > 0.05) on mean particle size, total phenolic content, and antioxidant activity between the first and final day of 1‐mo storage time. Additionally, uniform size and shape in TEM images supported the results.     

绿茶提取物对冷却羊肉保鲜作用的影响

为延长冷却羊肉的货架期,以云南圭山山羊肉为试验肉样,探讨不同浓度的绿茶提取物对冷却羊肉品质的影响。结果表明：提取物浓度为2%、4%、6% 的保鲜液均能有效抑制肠道菌群、假单胞菌和菌落总数的增长及挥发性盐基氮(TVB-N)和硫代巴比妥酸值(TBARS)的累积。2% 和4% 保鲜液处理的样品其色泽和感官评定值均显著优于对照组(p ＜ 0.05)。说明适当浓度的绿茶提取物可作为保鲜剂用于肉制品的贮藏。     

绿茶提取物的研究开发现状

该文介绍了绿茶提取物的研究现状,并对其所含成分、以及提取方法进行了简单阐述,同时,综述了其主要生理活性、应用情况和安全性评价,对其发展前景进行了展望。     

绿茶加工中主要滋味物质动态变化及其对绿茶品质的影响

以茶树品种‘碧香早’春季一芽二叶为原料,按照摊放、杀青、揉捻、干燥工艺将其加工成绿茶,在分析绿茶加工中水浸出物、茶多酚、氨基酸、咖啡碱、可溶性糖、儿茶素等主要滋味物质质量分数动态变化基础上,通过酚/氨比、简单儿茶素/酯型儿茶素比以及感官品质分析,探讨绿茶加工中主要滋味物质的动态变化及其对滋味品质的影响。结果表明：绿茶加工过程中,水浸出物、茶多酚、儿茶素、氨基酸、咖啡碱、可溶性糖等滋味物质质量分数整体上均呈逐渐下降的趋势,其中水浸出物、氨基酸、咖啡碱、可溶性糖质量分数在摊放过程中呈上升趋势;这些滋味物质的动态变化使得酚/氨比在摊放阶段由11.45下降到6.21,在杀青阶段逐渐上升到8.01,在揉捻和干燥阶段趋于稳定;而简单儿茶素/酯型儿茶素比在摊放阶段由0.43上升至0.45,在杀青阶段由0.47下降到0.44,在揉捻和干燥过程中逐渐缓慢降低至0.35;同时,这些滋味物质质量分数与绿茶滋味品质明显相关,当酚/氨比为5.5～6.5、简单儿茶素/酯型儿茶素比为0.3～0.5时,绿茶滋味品质由粗淡、苦涩逐渐转化为醇厚、鲜爽。     

一次发酵工艺对冷冻面团及馒头品质的影响

主要研究在不同发酵时间的条件下,一次发酵工艺对冷冻面团,馒头品质指标的影响,探讨馒头品尝评分与物性仪的TPA测试指标之间的关系,以及TPA测试在评价馒头加工品质中的应用。研究结果表明:最佳的发酵时间为15 min,在此条件下冷冻面团品质良好,馒头总评分最高。     

影响绿茶浸提液与胆酸盐结合的因素研究

在体外模拟人体消化环境,通过测定在不同pH值、离子强度、聚乙烯吡咯烷酮(PVP)和尿素浓度条件下,绿茶浸提液在体外对牛磺胆酸钠、甘氨胆酸钠、胆酸钠的结合能力,比较这些因素对绿茶浸提液结合胆酸盐的影响。结果表明,pH值、尿素浓度对绿茶浸提液结合胆酸盐有显著性影响(P≤0.05),离子强度对绿茶浸提液结合胆酸盐影响不显著(P≥0.05)。     

Optimization of Wheat-Grape Seed Composite Flour to Improve Alpha-Amylase Activity and Dough Rheological Behavior

In this work, the response surface methodology was used to determine the optimum level of input variables, gluten deformation index (mm) and the level of grape seed flour (%) addition in wheat flour that improve falling number index and Mixolab dough rheological parameters. The full factorial model was the best compatible model which fitted to each response. A replacement dose of 4.08% in wheat flour with gluten deformation index value of 8.27 mm was found optimal. The influence of optimum values of variables on dough microstructure has been investigated using epifluorescence light microscopy.     

茶多酚树脂吸附层析法脱咖啡因的性能研究

研究发现不同性质的吸附树脂对茶多酚提取液中的各组分具有明显不同的吸附选择性,极性RS-1树脂对茶叶水提液具有明显脱色除杂效果;具有较高比表面积的弱极性吸附树脂RX-2对咖啡因具有较高的吸附容量和吸附选择性,动态吸附时发生层析分离,是一种较为理想的咖啡因脱除剂。经两级树脂纯化,茶叶水提液中EGCG、ECG的含量可由49.78%、11.56%提高至74.72%、17.45%,收率分别约为78.31%、83.46%,处理后咖啡因含量可降至0.2%以下。     

绿茶水提物对蛋氨酸和胆碱缺乏饮食诱导的非酒精性脂肪肝炎小鼠的保护作用

为探究绿茶水提物对蛋氨酸和胆碱缺乏(MCD)饮食诱导的非酒精性脂肪肝炎的药效作用及其作用机制,将40只C57BL/6小鼠随机分为空白组(MCS组)、MCD组、绿茶水提物低浓度组(0.15 g/kg)和高浓度组(0.30 g/kg)。小鼠饲喂MCD饲料,建立非酒精性脂肪肝炎模型,造模同时给予绿茶水提物进行干预。8周后,测定血清的谷丙酸转氨酶(ALT)、谷草转氨酶(AST)、白介素6(IL-6)和肿瘤坏死因子-α(TNF-α)的浓度以及肝组织的甘油三脂(TG)和胆固醇(TC)浓度;油红染色检测肝组织脂肪堆积情况和HE染色对肝组织病理等级评定;Western blot检测葡萄糖调节蛋白78(GRP78)和微管相关蛋白轻链3(LC3)表达水平。结果发现,与模型组相比,绿茶水提物显著降低小鼠血清AST、ALT、IL-6和TNF-α水平,其最大降幅分别约为38%、45%、46%、74%,并且可以降低肝脏TG、TC水平以及减少脂肪堆积面积,TG和TC的最大降幅分别约为44%和37%,同时改善肝组织的脂肪变性、炎症反应和细胞气球样变。Western blot显示,绿茶水提物降低GRP78蛋白水平,同时升高LC3-II的表达水平。因此,绿茶对MCD饮食诱导的非酒精性脂肪肝炎小鼠模型有明显保护作用,其作用机制可能与GRP78蛋白和LC3蛋白相关。     

红茶、青茶和绿茶茶汤中硒溶出动态特性研究

为提供含硒茶的正确饮用方式,以红茶、青茶和绿茶作为研究对象,建立微波消解－原子荧光光谱法检测茶叶和茶汤中硒元素的定量分析方法,并揭示室温（25±2）℃下沸水浸泡的茶叶茶汤中硒元素溶出率随浸泡时间的变化规律。结果表明,茶叶和茶汤中硒元素检测的准确度、精密度、检出限、标准曲线线性范围和线性关系均符合定量分析方法学要求。所选红茶、青茶（乌龙茶）和绿茶中的硒元素含量分别为104.27、149.48 μg/kg和179.93 μg/kg。在室温（25±2）℃下,当茶水比为1∶200（g/mL）,用沸水浸泡时,红茶、青茶（乌龙茶）和绿茶中硒溶出率达到峰值的时间分别为20、60 min和120 min,溶出率分别为68.31%、65.44%和67.51%。随着浸泡时间的延长,水温有规律下降的同时,茶汤中硒的质量浓度也以不同速率下降。当浸泡时间达到5 h时,红茶和青茶中硒的质量浓度分别下降到10.09 μg/kg和 10.35 μg/kg,而绿茶中硒的质量浓度为 83.31 μg/kg。     

Modelling Wheat Flour Dough Proofing Behaviour: Effects of Mixing Conditions on Porosity and Stability

Kinetics of porosity and stability of dough expansion during proofing have been fitted with Gompertz and exponential models, respectively, for 24 distinct mixing conditions and same dough composition. Data for 10 conditions were used to relate the parameters of the models to mixing variables, specific power, and texturing time, through power regression models. Interpretation of the relationships between the mixing variables and the parameters of the Gompertz and exponential models emphasises the influence of dough rheological properties on dough expansion during fermentation and likely on bubbles distribution. The prediction performances of these porosity and stability models were evaluated using the root mean square error and mean absolute percentage error, for time series of the remaining 14 mixing conditions. The results show that integrating the mixing variables into the models significantly improves the prediction accuracy compared to control models whose parameters values are arithmetic means. Finally, we present an application where the mixing variables are determined in order to obtain a dough exhibiting the desired features during proofing, such as high levels of porosity and stability. Intensive mixing yields the best result but a more interesting trade-off can be obtained with intermediary mixing processes.     

绿茶提取液制备金纳米粒子及其在VC比色分析中的应用

以绿茶提取液为还原剂和保护剂,简单快速绿色制备金纳米粒子.与传统方法制备的金纳米粒子相比,绿茶提取液制备的金纳米粒子耐高盐耐酸碱,具有更好的稳定性.将金纳米粒子与VC和AgNO3混合,VC还原AgNO3产生银单质覆盖在金纳米粒子表面,形成金银核壳纳米粒子,导致溶液颜色及波长410 nm处吸光度变化,实现VC的定性及定量...     

茶叶中的锶

采用原子吸收分光光度法对中国一些常用茶叶中的锶进行了测定,结果表明茶叶及茶汤中的锶含量丰富,饮茶对延年益寿有益。     

馒头坯在汽蒸过程中水分迁移特性研究

研究了不同加水量的馒头坯在汽蒸过程中水分的迁移特性。结果表明：在汽蒸过程中．随着加水量的增加,馒头坯总的吸水量呈先上升后下降,然后趋于平缓。加水量与馒头坯不同部分的水分含量呈显著正相关,汽蒸时间与馒头坯不同部分水分含量之间的相关性不显著。另外,加水量与馒头坯不同部分的吸水量之间的相关性不显著,在汽蒸前6min,水分向馒头坯内部各部分迁移的速率最快;在汽蒸过程中,馒头坯各部分的水分含量关系始终为表皮部分大于瓤部分,瓤部分大于中心部分。     

绿茶提取物、亚硝酸钠及其混合物对意式发酵肠质地的影响

研究不同处理条件对意式发酵肠在加工和冷藏期间质地的影响.结果表明:绿茶提取物(GTE)、亚硝酸钠(NT)和混合处理(GTE/NT)3种不同的处理方式对于质构特性中的硬度、胶黏度和咀嚼性有较大影响;而对弹性、凝聚性和回复性影响较小.对于硬度、胶黏度和咀嚼性,绿茶提取物(GTE)在各阶段普遍有降低作用;亚硝酸钠(NT)先降低后升高;混合处理(GTE/NT)则普遍有升高作用.     

Evaluation of Antioxidant Activity of Green Tea Extract and Its Effect on the Biscuits Lipid Fraction Oxidative Stability

ABSTRACT:  This article investigates the effect of green tea extract (GTE) on biscuits lipid fraction oxidative stability. The antioxidant activity of GTE was compared with commonly used synthetic antioxidant butylated hydroxyanisole (BHA). Biscuits were prepared in 3 variations. Control samples were prepared without addition of antioxidants. The other variations were prepared by adding BHA (0.02%) and GTE at 3 different levels: 0.02%, 0.1%, and 1%. Biscuits were subjected to sensory studies and instrumental and chemical analysis. Phenolic compounds of GTE characterized powerful antioxidant activities evaluated using free radical, 2,2-diphenyl-1-picrylhydrazyl method, compared with gallic acid and significantly better than BHA. Antioxidants added to the samples clearly slowed down the process of oxidation of fatty acids, inhibiting the monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) decomposition. Addition of GTE at the level of 1% gave an excellent antioxidant effect on the biscuits lipid stability, inhibiting hydroperoxides formation by about 47% to 73% compared with BHA, which showed about 16% to 60% inhibition. However, GTE did not improve significantly lipid stability, measured by anisidine value ( p -AV), and inhibited formation of secondary oxidation products only by 3.5%. After accelerated storage time, insensitivity of oxidized-like flavor was about 2 times higher for control samples compared to samples with addition of antioxidants. Moreover, after storage biscuits treated with natural antioxidant received a higher panel score of overall acceptance compared to samples with BHA. Using volatile compound formation as a marker of lipid oxidation, both GTE and BHA were effective inhibitors of the decomposition of hydroperoxides.