过滤法测定茶汤沉淀成分研究

以绿茶、黄茶、白茶为原料,采用过滤法测定茶汤化学成分变化,探讨茶汤沉淀组成成分,结果显示:(1)随着静置时间延长,沉淀物逐渐增加,其比例不断发生变化;(2)从比例上看不同茶类其比例不一样,绿茶沉淀构成比例从多到少依次是茶多酚、可溶性糖、氨基酸、咖啡碱;白茶与黄茶茶汤沉淀构成比例从多到少依次是茶多酚、氨基酸、可溶性糖、咖啡碱,为茶汤沉淀形成机制和茶饮料的开发提供基础研究。     

六堡茶茶汤中胶体颗粒及沉淀性状研究

黑茶主要由微生物发酵形成,六堡茶是典型的黑茶之一,发酵对茶汤胶体性质与茶乳酪的成分组成是否有影响,尚未明确。本文通过动态光散射、扫描电子显微镜和高效液相色谱等方法比较了六堡茶毛茶以及发酵后的成品茶茶汤的胶体颗粒性质。结果表明,六堡茶毛茶和成品茶的茶汤均存在丁达尔现象,即存在胶体体系。两种茶汤在冷却过程的浊度变化率逐渐减少,接近常温时,成品茶茶汤浊度增加率小于毛茶;两种茶汤中均存在球形或椭球形的胶体颗粒,且胶粒粒径与Zeta电位具有温度响应。室温下成品茶茶汤的胶体颗粒平均粒径(2131 nm)显著低于毛茶(3045.8 nm),成品茶Zeta电位绝对值(-24.8 mV)高于毛茶(-19.2 mV)。两种茶汤成分差异导致二者沉淀差异,成品茶固形物相对沉淀率(2.22%)少于毛茶(2.79%),成品茶沉淀主要成分为茶红素、茶褐素和多糖,占沉淀94.11%,毛茶则为多酚、蛋白质和多糖,占沉淀75.76%,两种茶汤沉淀中酯型儿茶素总量均高于非酯型儿茶素总量,其酯型儿茶素、蛋白质、多糖和黄酮较易参与沉淀形成。因此,发酵使成品六堡茶的茶汤的胶体颗粒的稳定性增加,使其形成的茶乳酪与发酵前存在明显的差异。本研究为黑茶饮料等食品的开发提供了理论基础。     

速溶茶加工中茶乳酪的形成及其对溶解性的影响

研究了速溶茶加工中由于冷却过滤温度降低导致茶乳酪的形成及低温去除茶乳酪对改进产品溶解性的作用,同时探讨了茶汤中不同成分参与茶乳酪形成的差异。结果表明,在相同低温条件下冷却,绿茶茶汤茶乳酪的形成量最多;各成分参与茶乳酪形成的相对量,在绿茶中以咖啡碱最高,其次是EGCG,而在红茶与乌龙茶中则以EGCG最高,其次是咖啡碱;降低冷却温度15℃,由于绿茶过滤除去了更多的茶乳酪沉淀,故对速溶绿茶的溶解性具有更好的改进作用。     

物化处理印染废水新工艺探讨（二）

4 混凝沉淀处理工艺 4.1 废水中污染物分散状态 废水中污染物颗粒的分散状态可分为粗分散系、胶态分散系及高分散系三类。 粗分散系 颗粒直径在0.2～200μm,包括涂料、金属粉、纤维杂质等。 胶态分散系 颗粒直径在1～500nm,包括分散染料、大部分高分子化合物、无机助剂、棉纤维共生物。 高分散系 颗粒直径在0.5～15久,包括活性染料、小分子有机物及部分无机物。 上述污染物除高分散系不易形成胶体颗粒外,大部分以胶体状态悬浮或浑浊状态存在于污水中。颗粒小,且带电的颗粒形成的比较稳定的分散体系难以凝聚沉降,但这种稳定性可以通过电性中和或吸附作用降低,形成凝聚体,从污水中分离出来。 4.2 混凝沉降工艺条件 选用硫酸亚铁(FeSO_4)作为混凝剂,用量约为0.3～1‰。车间废水进入原水集中池,经自然混合后,一般呈中性偏碱性,由原水泵提升进入斜管沉淀池。泵前加入石灰水、硫酸亚铁溶液、药剂与原水经泵机械混合,由沉淀池底部经由许多斜管间隙上升到沉淀池顶部溢出。水的平均停留时间为1h,充分混凝,大颗粒全部沉降在斜管间隙里。清水含部分不易沉降的小颗粒进入超声气浮池,完成混凝沉淀过程。     

茶叶饮料沉淀问题的探讨

本试验研究了温度、水的硬度、茶汤中化学成份的含量等三因素与茶场产生絮状沉淀的关系，并试验出解决这种絮状络合沉淀的办法；当水的硬度大于３ｍｇ／Ｌ，温度低于２０℃时沉淀物明显增加，如茶汤中咖啡碱与茶酚含量的比例适中，则可大大降低络合物的形成从而抑制絮状沉淀的产生；通过添加一定量的柠檬酸等化学物后，茶汤中絮状沉淀物明显减少。     

食品级Tween 80微乳对红茶茶汤沉淀控制作用的研究

为研究食品级Tween 80微乳对红茶茶汤沉淀的控制作用,采用加水滴定法制备了以Tween 80为表面活性剂,柠檬烯为油相,1,2-丙二醇、聚乙二醇400、无水乙醇为助表面活性剂的微乳体系,根据拟三元相图微乳有效区域面积、微乳增溶水相能力和微乳温度稳定性等指标确定了空白微乳的处方,并研究了微乳对红茶茶汤特性以及茶汤内沉淀组分含量的影响。结果表明,空白微乳处方为:表面活性剂和助表面活性剂质量比Km值5∶5,油相与表面活性剂质量比(简称油剂比)2∶8和1∶9;微乳液抑制红茶茶汤沉淀的最佳工艺为:油剂比1∶9、含水量60%、添加量3~5mL;微乳液处理后的红茶茶汤澄清透明无沉淀,茶汤中可溶性蛋白质、茶多酚、咖啡碱和儿茶素的保留率分别为98.8%、98.9%、98.1%和97.4%。     

绿茶饮料沉淀机制及澄清技术

绿茶饮料的加工技术中仍存在保色、保香和防沉淀等关键问题有待解决,其中沉淀现象是目前制约绿茶市场发展的重要因素之一。由于冷后浑的形成,茶汤性状不稳定,不能保持清澈透明的饮料特征,或在储藏过程中会逐渐形成沉淀;在茶饮料生产过程中,需采用各种方法去除冷后浑或阻止冷后浑的形成,以保障产品的澄清透彻。本文从参与绿茶饮料沉淀的主要生化因子(茶多酚、蛋白质、咖啡碱、金属离子)出发,深入探讨了茶多酚与蛋白质、茶多酚与咖啡碱、茶多酚与金属离子之间的络合机制;从物理法、化学法和生物法三个方面综合概述了绿茶饮料当前主要采用的澄清技术,并根据沉淀机制对绿茶饮料可行的澄清技术提出展望。     

制糖过程中泡沫的形成和消泡剂的消泡机理

综述制糖过程中的起泡成分、泡沫形成的条件及泡沫稳定存在的因素。消泡剂的进入系和匍展系数以及憎水颗粒的去润湿 作用，论述了消泡机理。     

酶澄清绿茶饮料研究

研究了不同种类酶对绿茶茶汤抗沉淀效果,并采用HPLC分析了经单宁酶处理后茶汤中酯型儿茶素的变化。结果表明,单宁酶、果胶酶、木瓜蛋白酶对绿茶茶汤抗沉淀影响达极显著水平。多酚类和咖啡碱都有不同程度地减少,但没有达到显著水平。经木瓜蛋白酶处理的茶汤蛋白质含量减少,氨基酸含量同其他处理样相比有一定的增加。结合方差分析和感官审评结果表明,单宁酶对绿茶茶汤抗沉淀效果最好,单宁酶最佳作用时间为2h。在一定范围内,随着单宁酶作用时间的延长,茶汤中酯型儿茶素的总量在不断减少,茶汤的透光率随着酯型儿茶素的减少在不断增大。     

水仙乌龙茶膨化前后滋味和香气成分分析

采用膨化工艺对水仙乌龙茶进行处理,分析膨化前后茶叶的香气和滋味成分的变化。结果表明:茶叶膨化后滋味成分中的水浸出物、灰分、咖啡碱与茶多酚的含量有所降低,而碳水化合物含量则有所提高。膨化后茶叶滋味成分的改变影响茶汤的滋味,咖啡碱和茶多酚的减少,使膨化后茶汤苦味和涩味变淡,而碳水化合物增加,使茶汤显得更加甘醇。茶叶膨化后,香型发生一定转变,原乌龙茶的特征成分吲哚、苯乙腈含量比例减少,橙花叔醇未检出,而热裂解产物吡嗪类、吡咯类化合物增加明显,使膨化茶叶呈现出类咖啡焦香味。     

Cream formation and main chemical components of green tea infusions processed from different parts of new shoots

The formation of green tea cream and its chemical components were investigated. The green tea infusions were processed from different parts of new shoots: the bud and the first leaf, the second leaf and its implicative stem, the third leaf and its implicative stem, and the fourth leaf and its implicative stem, which were named as first part, second part, third part and fourth part, respectively. The results showed that the formation of tea cream and its settlement slowed down gradually from the first part to the fourth part, and that the amount of tea cream also decreased accordingly. The amount of tea cream was influenced remarkably by the chemical components in the green tea infusion. The main components of green tea cream were polyphenols (29.86 –78.66%), total sugar (14.47–27.62%) and caffeine (2.35–10.43%). Catechins (12.8–42.5%) were the main components of polyphenols which participated in tea cream formation. The main components in the catechins were found to be (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), (−)-epicatechin (EC) and (−)-epicatechin gallate (ECG). Seven minerals were found in the tea cream, including Ca²⁺, K⁺, Mg²⁺, Mn²⁺, Na⁺, Zn²⁺ and Ni²⁺.     

Irreversible sediment formation in green tea infusions

The formation of irreversible tea sediment (IRS) and its chemical components in green tea infusions were investigated. The results showed that the amounts of IRS in the green tea infusions from various tea cultivars ranged from 0.10 to 1.47 mg/mL. The amount of IRS was influenced remarkably by the chemical components in the green tea infusion. Principal component analysis and regression analysis indicated that gallated catechins, Mn, Ca, caffeine, Na, and (-)-gallocatechin gallate (GCG) were the principal components. IRS (mg/mL) = -4.226 + 0.275 gallated catechins + 79.551 Na + 7.321 Mn + 21.055 Ca + 0.513 caffeine - 0.129 GCG (R2 = 0.697). The contents of the main chemical components in the reversible tea sediment (RTS) and IRS were markedly different, especially the minerals. Large amount of minerals participated in the formation of irreversible green tea sediment. The amount of IRS increased with the extraction temperature.     

茶多酚和咖啡碱对茶乳酪形成的影响

采用茶多酚和咖啡碱模拟构建茶乳酪成因体系,通过分析溶液的透光率、粒径、沉淀量、咖啡碱和儿茶素含量的变化,综合评价茶多酚和咖啡碱对茶乳酪形成的影响。结果表明：随茶多酚和咖啡碱质量浓度的增加,其聚合后溶液的透光率从95.5%降为24.7%;粒径从198 nm增加到475 nm;沉淀量由8 mg/L增加到244 mg/L;当固定咖啡碱或茶多酚中任一物质的质量浓度,随另一物质质量浓度的增加,上述变化趋势增强。通过分析检测咖啡碱和儿茶素各单体在模拟反应体系中的变化,表明咖啡碱和表没食子儿茶素没食子酸酯（epigallocatechin-3-gallate,EGCG）是模拟体系中茶乳酪形成的关键组分。因此,尽量选用咖啡碱含量低于200 mg/L、茶多酚含量低于1 200 mg/L的绿茶原料,可避免茶乳酪的大量生成,增强绿茶饮料透亮的感官效果。     

Effect of tannase treatment on protein-tannin aggregation and sensory attributes of green tea infusion

Effect of tannase enzymatic treatment on protein-tannin aggregation and sensory attributes of green tea infusion was investigated. Green tea leaves were extracted with hot water at 85 °C for 20 min, the tea infusion was then treated with tannase. Results showed that both EGCG and ECG of the tea catechins were hydrolyzed by tannase into EGC and EC, respectively, accompanied by production of gallic acid. The tannase-treated tea infusion had a relatively lower binding ability with protein. Changes in the content of tea catechins, formation of tea cream, and turbidity of tea infusion with or without tannase treatment were measured after 4 weeks. Content of catechins in the tannase-modified tea remained almost unchanged, while those without tannase treated (control) decreased significantly (p < 0.05). Meanwhile, better color appearance and less tea cream formation were observed for the tannase-treated green tea, and tea cream formed for the control after storage. Results of the sensory evaluation showed that mouth feeling, taste and the overall acceptance of the tannase-treated green tea infusion were all better than those of the control.     

绿茶浓缩汁中不可逆沉淀形成的研究

为研究绿茶浓缩汁中不可逆沉淀的化学组成及其形成过程,本文分析了茶浓缩汁中不可逆沉淀与可逆沉淀的主要化学组成,及低温条件下不同贮藏阶段（0~20 d,20~180 d,180~250 d）不可逆沉淀与可逆沉淀的形成情况。研究结果表明,不可逆沉淀含有大量金属元素和草酸根离子,而可逆沉淀主要由茶多酚、碳水化合物、咖啡碱、蛋白质及黄酮化合物组成;浓缩汁沉淀以可逆沉淀为主,不可逆沉淀较少;随着贮藏时间延长,沉淀量逐渐增加,但大部分可逆与不可逆沉淀都在0~20 d形成;元素Mg、Mn、Ga、Ni和Zn主要是在0~20 d参与不可逆沉淀形成,Fe和Cu主要在20~180 d,而Al和Ca主要是在180~250 d。另外,本文还验证了鞣花酸能与蛋白质结合产生不可逆沉淀。本文结果说明绿茶浓缩汁不可逆沉淀主要是不溶性草酸盐。     

花香绿茶饮料的生化成分变化及物性特征

研究以花香绿茶为原料的茶饮料在高温灭菌前后及分别在37 ℃和4 ℃条件下贮藏7 d后,茶汤色差、透光率、粒径、沉淀量和沉淀微观结构以及茶多酚、氨基酸、蛋白质、黄酮、水溶性总糖、咖啡碱和儿茶素组分常规化学成分含量的变化规律。结果表明：1）4 ℃贮藏在一定程度上可有效缓解茶饮料色泽的劣变和保持较好的澄清度,37 ℃贮藏则加速汤色黄化和浑浊;2）不同的贮藏方式对生化成分含量的影响差异显著,4 ℃贮藏能够保持较高的生化成分含量,37 ℃贮藏易使品质风味显著劣变,生化成分含量显著减少;3）4 ℃贮藏生成的沉淀量要比37 ℃贮藏少,4 ℃贮藏生成的沉淀由许多小分子颗粒聚集而成,而37 ℃贮藏生成的沉淀则是由大块的分子团聚集而成。     

Effect of pH on cream particle formation and solids extraction yield of black tea

Effect of pH on tea solids extraction yield was significant in increasing instant tea yield. Solids extraction yield was doubled when tea was extracted at pH 1.2 compared with that extracted in boiling distilled water with pH 6.8. H⁺ encouraged black tea cream particle formation by either releasing more solids into the infusion or stimulating polyphenols to interact with polysaccharides and nucleophilic groups on protein in tea infusions. HPLC results revealed that theaflavins and tea catechins were leading substances affecting the formation of cream particles and infusion colour. Theaflavins and some tea catechins, such as EGCG, ECG and EGC, were dissociated or degraded under alkaline conditions and thus tea cream particles tended to dissolve and tea infusion became dark in colour. Feasibility of stepwise extraction of instant teas used for iced tea and normal drinking tea, by controlling temperature and pH, is also considered in the present paper.     

The solubility of tea cream

The heterogeneous nature of tea cream, with regard to solubility, is shown. A simple three-component system enables some of the observed cream characteristics to be explained. Suggestions are made concerning the compositions of these components and a model for the formation of cream particles, from a hot infusion, is proposed. Extraction of leaf tea with cold water gives an infusion incapable of creaming.     

Cream formation in a semifermented tea

The formation of cream in Paochung tea, a popular semifermented tea, which undergoes a lesser degree of enzymic oxidation during manufacture, was investigated at various extraction temperatures, extraction times, pHs and leaf/water ratios. The primary components of Paochung tea cream were catechins (30%), caffeine (20%) and protein (16%). (−)-Epigallocatechin gallate and (−)-epicatechin gallate were the major catechins precipitated during creaming, constituting 19% and 5% of the tea cream respectively. The amount of tea cream produced and its composition were influenced by extraction temperature and pH. The tea leaf/water ratio determined the amount of tea cream formed but did not affect the cream composition. Catechins were considered to be the key component in tea cream. They interacted with caffeine and protein to induce tea cream formation. © 1999 Society of Chemical Industry     

绿茶茶汤中黄酮醇及其苷类的测定方法以及对茶汤色度的影响

黄酮醇及其苷类物质是构成绿茶汤色的重要组分。绿茶中含有20多种黄酮醇及其苷类物质,其中以槲皮素、杨梅素、山柰素的3种苷类物质为主。文中采用高效液相色谱法研究了绿茶茶汤酸水解前后槲皮素、杨梅素、山柰素的含量变化,建立了黄酮醇及其苷类含量的检测方法。利用正交实验方法得到茶汤水解的优化条件为:5 mL的茶汤中加15 mL纯甲醇、5 mL 6 mol/L HCl,在75℃下水解时间2h,芦丁的平均水解率为82.74%。对不同贮藏期间茶汤色度与黄酮醇及其苷类的相关性进行了研究,结果表明:茶汤贮藏过程中随着茶汤的红绿度(a)和黄蓝度(b)不断升高,杨梅素苷含量逐步下降,杨梅素苷与茶汤的红绿度、黄蓝度的相关系数分别为:-0.982 1、-0.882 6,但与茶汤明亮度(L)的相关性不显著。槲皮素和山柰素及其苷类与茶汤色泽变化关系不密切。