改性蒙脱石粉脱除绿茶提取液中咖啡因的工艺优化

首先对蒙脱石粉进行了改性,得到改性蒙脱石粉;其次,以咖啡因的脱除率、茶多酚的损失率和茶多酚与咖啡因的相对分离度作为评价指标,研究了温度、时间、用量和pH 4个工艺参数对改性蒙脱石粉脱除绿茶提取液中咖啡因的影响。结果表明,4个工艺参数的较适宜值分别为改性蒙脱石粉用量4%、吸附时间2 h、吸附温度45℃和绿茶提取液p H2.5;在较适宜条件下,咖啡因的脱除率为89.39%,咖啡因/EGCG的相对分离度为7.87,为脱咖啡因绿茶提取液的研究提供了依据。     

超临界流体技术脱除绿茶中咖啡因和儿茶素的研究

通过正交实验确定了超临界流体脱除茶叶中咖啡因的最佳工艺参数。结果表明,茶样形态对咖啡因脱除影响极大,60目磨碎茶样的咖啡因脱除率可达85.63%,咖啡因含量≤0.5%;含水率对茶叶中咖啡因的脱除率影响也较大,含水率为35%～50%时较适宜。超临界流体萃取后的磨碎处理茶样品质总分均要好于其它处理,品质和口感得分接近于对照。正交实验中,咖啡因脱除率的影响因子主次顺序为压力>温度>动态循环时间>夹带剂用量,而对儿茶素来说,夹带剂的影响较为明显。     

茶叶脱咖啡因技术的研究进展

茶叶中含有的活性成分主要是茶多酚和咖啡因,茶多酚在抗氧化、抗病毒和降血脂等方面具有积极的调节作用,但是咖啡因对人体的健康存在有潜在的副作用,会导致高血压和流产等不良危害,因此,脱除茶叶中的咖啡因、保留茶多酚的研究受到广泛关注。该文主要对化学溶剂提取法、物理吸附法和生物降解法脱除茶叶中咖啡因的研究进展进行综述。     

聚酰胺色谱法分离制备茶多酚的研究

研究了利用聚酰胺分离制备茶多酚的工艺条件:在柱尺寸为120×30mm、茶多酚吸附量为50mg/g(干树脂)时,先用120mL、5%的乙醇溶液以1.0mL/min的流速洗脱咖啡因,再用285mL、70%乙醇与0.5%的复合洗脱液在1.5mL/min的流速下分离色素与茶多酚,茶多酚的回收率平均为59.4%,咖啡因的脱除率为96.3%。整个提取过程茶多酚的总得率平均为19.2%(以干茶叶计),产品纯度为92.1%,高效液相色谱(HPLC)分析各种儿茶素的含量为EGCG:33.3%;EGC:18.8%;ECG:8.8%;EC:2.6%;C:0.5%;GA:1.0%;儿茶素总含量为65.1%,咖啡因含量仅为1.04%。     

真空升华法脱除绿茶中咖啡碱工艺研究

根据咖啡碱升华的理化性质,本文采用真空升华法脱除炒青绿茶中的咖啡碱,并研究了其最佳工艺参数及此工艺对炒青绿茶品质的影响。结果表明,茶样中的咖啡碱处于结合态,不易升华,所以直接对茶样进行真空升华处理,茶样中咖啡碱的脱除率未超过15%。研究不同预处理对咖啡碱脱除效果的影响,发现水浸润预处理结合超声-微波协同萃取仪预处理,对咖啡碱的脱除最为有效。真空升华最佳工艺为:将茶样用2倍于其质量的水浸润后,采用超声-微波协同萃取仪在微波功率300W、超声功率50W条件下处理60s后在90℃条件下真空升华处理4h,所得茶样咖啡碱脱除率为62.24%,主要有效成分茶多酚损失率低于10%,且非酯型儿茶素的损失量大于酯型儿茶素。     

六堡茶中咖啡因加速溶剂萃取(ASE)的工艺研究

本研究探讨了加速溶剂萃取(ASE)法提取六堡茶中咖啡因。采用快速溶剂萃取仪提取六堡茶中咖啡因,以乙醇为萃取溶剂,利用单因素试验考察乙醇浓度对提取率的影响,设置仪器压力为10MPa,选择萃取温度、萃取时间、循环次数等影响咖啡因得率的因素进行L_9(3~4)正交试验,以咖啡因得率为主要指标,考察ASE法最佳提取条件并与微波辅助提取法进行比较。结果显示ASE法提取六堡茶中咖啡因的最优化条件是以无水乙醇为溶剂,在温度120℃条件下静态萃取3次,每次10min;经ASE法提取,咖啡因的平均得率为20.374mg/g,其提取物经过C18固相萃取小柱处理不仅能除去六堡茶提取液中的大部分杂质,而且对咖啡因的含量几乎没有影响,经微波辅助法提取,咖啡因的平均得率为17.028mg/g。说明ASE法提取六堡茶中咖啡因,其提取率高于微波辅助提取法,且能保证提取物的质量。     

茶多酚水溶液浸提法生产低咖啡碱茶叶的研究

首次采用茶多酚水溶液浸提法脱除鲜茶叶与干茶叶中的咖啡碱,并保留其中的主要功能性成分茶多酚。鲜茶叶最佳浸提条件为:温度100℃,料液比1:10(g/mL),茶多酚水溶液质量体积分数5%,时间5min。此条件下咖啡碱脱除率达80.61%,比传统热水浸提法提高31.25%,且茶多酚无损失。干茶叶最佳浸提条件为:温度100℃,料液比1:20(g/mL),茶多酚水溶液质量体积分数15%,时间7min。此条件下咖啡碱脱除率达81.61%,且处理后的茶叶中茶多酚含量提高90.02%。研究结果表明,针对鲜茶叶和干茶叶原料,茶多酚水溶液浸提法均能有效脱除其咖啡碱,并有效保留或提高茶叶中的茶多酚,比传统热水浸提法有明显优势,是一种生产低咖啡碱茶叶的新方法。     

超声波、微波辅助萃取鹌鹑蛋黄卵磷脂的研究

探索超声波、微波辅助萃取鹌鹑蛋黄卵磷脂工艺条件,在单因素水平试验基础上进行正交试验优化工艺条件。结果表明:超声波萃取最佳工艺为V(乙醇):V(乙醚)=2:1,溶剂用量为4倍蛋黄体积,萃取时间30 min,萃取2次,萃取率达87.5%;微波萃取最佳工艺为萃取液用体积分数95%乙醇,pH值8.5,料液比1:4,辐射功率650W,辐射时间40s,萃取率为88%。     

应用醋酸乙酯从茶汤中萃取茶多酚的研究

茶多酚是茶叶中主要生理活性物质，其制造方法一般采用液－液萃取工艺，以醋酸乙酯为溶剂，从茶汤中萃取出茶多酚。本文研究了醋酸乙酯的含水量对茶多酚萃取率的影响，从而确定为降低生产成本，水相与溶剂的容积比应为２：１。     

大豆油对绿茶汤中咖啡因脱除作用的研究

通过大豆油脱除绿茶汤中咖啡因的试验,对温度、萃取比例、萃取次数等影响咖啡因脱除率的因素进行研究,提出了大豆油脱除绿茶汤中咖啡因的合适萃取条件。     

Decaffeination of fresh green tea leaf (Camellia sinensis) by hot water treatment

Hot water treatment was used to decaffeinate fresh tea leaf in the present study. Water temperature, extraction time and ratio of leaf to water had a statistically significant effect on the decaffeination. When fresh tea leaf was decaffeinated with a ratio of tea leaf to water of 1:20 (w/v) at 100 °C for 3 min, caffeine concentration was decreased from 23.7 to 4.0 mg g⁻¹, while total tea catechins decreased from 134.5 to 127.6 mg g⁻¹; 83% of caffeine was removed and 95% of total catechins was retained in the decaffeinated leaf. It is considered that the hot water treatment is a safe and inexpensive method for decaffeinating green tea. However, a large percentage of tea catechins was lost if rolled leaf and dry tea were decaffeinated by the hot water treatment and so the process is not suitable for processing black tea.     

黄茶加工中主要品质成分的动态变化

以茶树品种碧香早夏季一芽一叶鲜叶为原料,按照摊放、杀青、揉捻、闷黄、干燥的传统黄茶加工工艺,将其加工成黄茶,通过对其中11 个有代表性的工艺点取样,并进行茶多酚、儿茶素、氨基酸、水浸出物、可溶性糖、咖啡碱、黄酮含量检测,以及感官审评和香气品质成分分析,探讨黄茶加工过程中主要品质成分的动态变化。结果表明,在黄茶加工过程中,滋味物质茶多酚、儿茶素总量、水浸出物、可溶性糖、咖啡碱以及黄酮含量均在整体上逐渐降低,其足干茶样含量相对茶鲜叶的降幅分别为30.12%、24.08%、10.97%、61.34%、33.20%、25.55%,而游离氨基酸含量则有所增加,其足干茶样含量相对茶鲜叶的增幅为19.46%,其中茶多酚、咖啡碱、黄酮以及氨基酸含量在摊放过程中有所上升;香气物质中,足干茶样的醇类、酮类、烯烃类、酯类化合物的相对含量相较于茶鲜叶分别减少了17.18%、5.51%、5.77%、2.10%,而醛类、酚类化合物的相对含量则分别增加了35.35%、4.06%;从加工工艺看,黄茶滋味品质主要受摊放与闷黄工序的影响,摊放过程中氨基酸含量随着摊放时间的延长而增加,而闷黄过程可使酯型儿茶素转化为简单儿茶素,并在此工艺中产生茶黄素,是黄茶醇鲜爽滋味及“黄汤黄叶”品质形成的主要因素,同时闷黄时间为8 h时,滋味品质较好;香气品质则主要受摊放、闷黄和干燥工序影响。     

低共熔溶剂提取绿茶总黄酮及其抗氧化活性

目的:优化低共熔溶剂提取绿茶总黄酮工艺,并评价其抗氧化活性。方法:以总黄酮提取率为考察指标,以低共熔溶剂种类、液料比、提取温度和提取时间为影响因素,采用正交试验优化低共熔溶剂提取绿茶总黄酮工艺参数,并对其抗氧化活性进行评价。结果:绿茶总黄酮的最优提取工艺为以80%乙酰胆碱—乳酸(n_乙酰胆碱∶n_乳酸=1∶1)水溶液为低共熔溶剂,液料比(V_溶剂∶m_绿茶)30∶1(mL/g),提取温度90℃,提取时间75 min,此条件下绿茶总黄酮提取率为1.84%,总黄酮质量浓度为65.8 mg/mL。一定质量浓度范围内,绿茶总黄酮提取液对DPPH自由基和OH自由基的清除能力强于维生素C。结论:以80%乙酰胆碱—乳酸(n_乙酰胆碱∶n_乳酸=1∶1)水溶液为低共熔溶剂提取的绿茶总黄酮具有一定的抗氧化活性。     

SUBCRITICAL WATER EXTRACTION OF CAFFEINE FROM BLACK TEA LEAF OF IRAN

ABSTRACT

This study examines subcritical water extraction (SCWE) of caffeine from black tea leaf. The effects of various operating conditions such as water temperature (100, 125, 150 and 175C), water flow rate (1, 2 and 4 g/min), mean particle size (0.5, 1 and 2 mm) on extraction yield and rate were determined. SCWE at 175C, water flow rate of 2 g/min and mean particle size of 0.5 mm were found to be able to recover 3.82% (w/w) of caffeine present in the black tea leaf within 3 h of extraction. In comparison to the SCWE, conventional hot water extraction showed 3.30% (w/w) extraction yield. It was found also that pressure had no effect on extraction yield and rate.

PRACTICAL APPLICATIONS

Recently, subcritical water has become of great interest as an alternative solvent for extraction of natural active compounds. Subcritical water, as a green solvent, can be used in many different fields of applications. In recent years, extraction of flavors, fragrances and antioxidant components from plant materials, and hydrolysis of carbohydrates, vegetable oils and fatty acids have been widely investigated by many researchers. Using subcritical water for analytical purposes, for soil remediation and applying it as a reaction media are some other interesting fields for practical applications. Subcritical water is an excellent solvent for caffeine as well as many other organic compounds but is safer than the organic solvents that are used for caffeine extraction.     

‘巴山早’紫色芽叶红茶加工工艺研究及品质评价

为了探究‘巴山早’紫色芽叶的红茶加工工艺及其制茶品质特点。本研究选用‘巴山早’紫色芽叶为原料,在万源红茶加工工艺基础上进行工艺优化,对红茶关键加工技术（萎凋、发酵和干燥）进行单因素实验和正交试验,以感官评分、茶黄素和茶红素之和与茶褐素的比值TFRB为评价指标,确定紫色芽叶红茶的最优工艺参数,探究关键加工技术不同参数对红茶品质的影响;以‘福鼎大白’绿色芽叶为对照,采一芽一叶新梢,按照优化后的加工工艺加工成红茶,所制茶样与‘巴山早’紫色芽叶红茶通过感官审评、内含品质成分测定分析和香气组分检测分析。结果表明,‘巴山早’紫色芽叶红茶的最优加工工艺为萎凋时间21 h,发酵时间4.5 h,干燥温度90±2℃,此时感官评分最高为92.83±0.19,‘巴山早’紫色芽叶红茶的感官品质优于对照,其茶多酚、氨基酸、可溶性糖、水浸出物、咖啡碱、茶黄素和茶红素含量分别为12.58%、3.62%、2.89%、37.89%、4.61%、0.38%和3.57%,均高于对照,TFRB为1.07是其滋味鲜醇,汤色红亮的物质基础;氨基酸组分总量、呈鲜爽味氨基酸组分和呈甜味氨基酸组分含量分别为32.35、22.68和3.4...     

Effects of cosolvents on the decaffeination of green tea by supercritical carbon dioxide

Due to the adverse effects of the caffeine in a variety of plant products, many methods have been explored for decaffeination, in efforts to remove or reduce the caffeine contained in plant materials. In this study, in order to remove caffeine from green tea (Camellia sinensis) leaves, we have employed supercritical carbon dioxide (SC–CO₂), which is known to be an ideal solvent, coupled with a cosolvent, such as ethanol or water. By varying the extraction conditions, changes not only in the amount of caffeine, but also in the quantities of the principal bioactive components of green tea, including catechins, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC), were determined. The extraction conditions, including temperature, pressure and the cosolvent used, were determined to affect the efficacy of caffeine and catechin extraction. In particular, the type and concentration of a cosolvent used constituted critical factors for the caffeine removal, combined with minimal loss of catechins, especially EGCG. When the dry green tea leaves were extracted with SC–CO₂ modified with 95% (v/v) ethanol at 7.0 g per 100 g of CO₂ at 300 bar and 70 °C for 120 min, the caffeine content in the decaffeinated green tea leaves was reduced to 2.6% of the initial content. However, after the SC–CO₂ extraction, a substantial loss of EGCG, as much as 37.8% of original content, proved unavoidable.     

Changes in antioxidant phytochemicals and volatile composition of Camellia sinensis by oxidation during tea fermentation

Monomeric flavonoids (flavan 3-ols or tea catechins) present in Camellia sinensis leaf are transformed to polymeric theaflavin and thearubigin by oxidation occurring during tea fermentation. The distinctive colour, decreased bitterness and astringency, and characteristic flavour are derived from the fermentation process giving fermented teas a marked distinction from non-fermented green tea. Even though teas are available in many different fermentation levels from green to black, the difference in phytochemicals and volatile compounds in teas with different degrees of fermentation has not been fully investigated yet within the same tea leaf. The objective of this study was to observe non-volatile phytochemicals including polyphenolic and volatile compounds changes by oxidation under strict processing control and to evaluate the degree of fermentation for the maximum antioxidant capacity with the same tea material. Harvested tea leaf was immediately processed to different degrees of oxidative fermentation (0%, 20%, 40%, 60%, and 80%). Tea infusions brewed with each processed tea leaf were analysed for polyphenolic profile, total soluble phenolics, antioxidant capacity, and volatile profile using LC–MS, HPLC, Folin–Ciocalteu assay, Oxygen Radical Absorbance Capacity (ORAC), and GC–MS analyses. The flavonoids in non-fermented green tea were significantly lessened during the oxidative fermentation process and the decreased monomeric flavonoids were transformed to polymeric theaflavin and thearubigin as the leaves were more processed. Total soluble phenolics and antioxidant capacity were significantly higher as tea leaves were less processed with a high correlation with individual polyphenolic changes. Volatile compounds present in tea leaf were analysed by GC–MS to observe changes due to processing and were utilised to create a model to differentiate fermentation based on volatile composition. Twenty-four compounds were used to build an initial model which was optimised to 16 compounds with complete separation of the groups using discriminant function analysis. The data suggested that fermentation diminished antioxidant capacity of tea and could result in lowering potential health benefits from flavonoids. This result should be considered for tea manufacturing and the development of functional foods desiring maximum potential health benefits from antioxidant flavonoids in tea.     

3种紫芽茶不同成熟度芽叶特性及生化成分分析

目的 研究不同成熟度紫芽茶芽叶特性及生化成分相关性。方法 以思茅茶树良种场资源圃的紫娟、丹妃、水塘黑茶3个品种为原料，采用茶树种质资源描述规范法、高效液相色谱法分析茶树品种、芽叶特性与成熟度对茶叶内含成分的相关性。结果 供试样内含成分随成熟度呈现不同程度的显著性差异，其中花青素含量与芽叶红紫色深浅程度呈正相关，与成熟度呈负相关；茶多酚、咖啡碱、儿茶素、水浸出物同成熟度呈现显著性负相关；不同成熟度氨基酸含量变化1.09%~5.85%，其中含量最高的是水塘黑茶，其次是丹妃；咖啡碱含量2.58%~5.76%，其中含量最高的是紫娟，其次是丹妃；茶多酚含量6.36%~31.21%、花青素含量0.14 mg/g ~3.63 mg/g、儿茶素含量2.42%~24.03%、水浸出物含量22.93%~41.30%，其中含量最高的均是丹妃。结论 紫色品种茶中的内含成分丰富，具有较高的茶多酚、咖啡碱、氨基酸和儿茶素，丹妃内含成分含量较高，可作为高产优质、高花青素茶树品种的选育对象。     

茶叶咖啡碱分离提取新技术研究

本文以中、低档绿茶为原料,研究了咖啡碱分离提取技术,结果表明:微波水提结合乙酸乙酯萃取应用于茶叶中咖啡碱的提取具有短时、高效、产品无毒性等优点。确定咖啡碱最佳萃取条件为:供试液中NaCl浓度0.2%,二倍量的乙酸乙酯萃取三次,咖啡碱萃取率达95.14%。经升华纯化后,咖啡碱得率为1.2%,纯度为98.2%;紫外光谱分析证实,该工艺分离对咖啡碱制品的化学结构无影响。