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.     

微波提取芦笋茶黄酮工艺的研究

实验研究了从芦笋茶中提取黄酮化合物的微波条件，并探讨了芦笋茶黄酮化合物的抗氧化活性。分别研究了提取时间、乙醇浓度和料液比对黄酮得率的影响，结果表明，提取时间为45s、乙醇浓度80％、料液比（g／mL）为1：25时提取效果最佳，黄酮得率为88．0％。三个因素对黄酮得率影响的大小顺序为：乙醇浓度〉时间〉料液比。实验还研究了芦笋茶黄酮化舍物对自由基的清除能力和抗脂质过氧化能力。结果表明：芦笋茶中黄酮提取物有较强的自由基清除能力和一定的抗脂质过氧化能力，当样品液黄酮浓度为0．66mg／mL时，其对自由基的抑制率为91．2％；当样品液黄酮浓度为1．32mg／mL时，其对脂质过氧化物的抑制率为14．4％。     

微波提取茶叶中咖啡因工艺的研究

采用微波提取方法，微波功率为500W，以茶叶中提取咖啡因的含量为考察指标，研究提取溶剂浓度、料液比、提取时间等因素对咖啡因提取率的影响。通过正交试验，确定微波提取茶叶中咖啡因的最佳工艺条件为：提取溶剂50％乙醇，料液比1：8，提取温度180℃，提取时间14min。     

超声波法提取普洱茶多糖的工艺

采用超声波浸提法从普洱茶中提取多糖,用硫酸-苯酚法显色,在490nm处运用分光光度计测其含量;考察了超声波功率,浸提固液比,超声波处理时间对多糖提取率的影响,并以正交试验设计优化工艺条件,结果表明:影响普洱茶多糖提取率因素的主次关系是功率>浸提固液比>时间.正交实验最佳条件:功率800W,固液比1:50,时间25 min,为提取普洱茶多糖的开发提供了可靠的实验依据.     

非水溶性茶蛋白的提取工艺研究

茶叶中含有15%-30%的蛋白质,其中大部分不溶于水,易溶于碱。本文研究了采用碱法从茶叶中提取非水溶性茶叶蛋白的工艺。实验结果表明:当NaOH溶液浓度0.07mol·L-1、温度90℃、时间30min、固—液比1:40时蛋白质的提取率最高为61.1%。通过调节提取液pH值的方法制备粗蛋白,粗蛋白纯度为54.45%。     

微波辅助水提葡萄籽原花青素的研究

对微波辅助从葡萄籽中提取原花青素的工艺进行了研究，在单因素和正交优化设计的实验基础上。确定了微波辅助提取葡萄籽原花青素的最佳工艺条件，即微波功率为中高火，料液比为1：18（g／mL），微波作用时间为70s，然后在沸水浴中浸提80min。微波辅助浸提法所得原花青素的提取率比单用传统水提法提高了约1倍。     

STUDIES ON EXTRACTION AND ISOLATION OF FLAVONOIDS FROM GINKGO LEAVES

The leaf of Ginkgo (Ginkgo biloba L.) contains various substances that are considered to have health-promoting properties. Most of these biologically active substances fall into two groups: flavonoids and terpenoids. This paper describes a method to extract and isolate flavonoids from Ginkgo leaves. The method consists of extraction with an ethanol solution and isolation with affinity column chromatography. Results show that 50% ethanol gave a better extraction yield than 70% ethanol while 20% or 40% ethanol concentration was the choice as a wash solvent. The highest yield resulted from the use of 50% ethanol as extractant and 40% ethanol as wash solvent. This combination produced a final extract with a flavone glycoside concentration as high as 24.31%, constituting about 3.7% of the dry matter in the original leaves. The procedure is rather simple and readily adaptable for commercialization.     

超声波提取潮州凤凰茶茶多酚的工艺研究

以潮州凤凰茶为原料,用超声波法提取茶多酚,通过正交试验确定最佳提取工艺.结果表明最佳提取条件为:70℃、100W超声辐射下用80%乙醇按料液比1:10提取20min.该法与常规溶剂提取法相比,具有提取时间短,产率高,氧化损耗小等特点.     

黄浆水中大豆异黄酮的回收——黄浆水的预处理

为了提高混合活性炭吸附法回收豆制品加工黄浆水中大豆异黄酮的效率，对黄浆水进行预处理。最佳工艺条件为调节废水pH=7．5，按废水固形物含量的10％加入CaCl2，加热至100℃，处理15min，滤其沉淀后，再进行超滤,最佳操作条件为压力0．3NPa-0．4MPa，温度40℃-50℃，滤膜PS-10，截留分子量10000。经预处理后，黄浆水中蛋白质去除率为95．3％，大豆异黄酮损失率12．9％。     

酯交换法从蔗蜡中提取高碳脂肪醇的研究

研究探讨酯交换法从蔗蜡中提取高碳脂肪醇的工艺条件,通过正交试验,得出最优工艺条件:以丁醇为溶剂,料液比为1:15,反应时间为4 h和0.1%KOH醇溶液为催化剂,此时高碳脂肪醇的得率为:16.75%～17.34%.通过GC-MS对高碳脂肪醇分析检测,二十八烷醇含量为67.09%.     

复合酶法提取茶多酚工艺条件研究

实验采用复合酶解法在低温下提取茶叶中的活性物质——茶多酚。采用单因素和正交实验确定了最佳提取条件。结果表明，采用复合酶法提取茶多酚，提取率高达98％以上，茶多酚中的活性成分儿茶素相对含量较传统沸水提取法高出9％～10％。     

利用豆渣、黄浆水发酵生产曲酸的研究

实验以豆腐渣、黄浆水为主要原料利用米曲霉发酵生产曲酸,对发酵生成曲酸所需添加的各种营养因素和发酵条件进行了研究。得出该茵利用豆渣的最佳发酵培养基为:豆渣80％、麸皮24％、酵母膏1.2％、Mg-SO4·7H2O 0.16％,pH为自然;接种量为10％,每250mL三角瓶装量为50g,在30℃发酵培养,5～6d菌体生长量和曲酸产量最大。米曲霉利用黄浆水生产曲酸的最佳发酵培养基为:葡萄糖12％、酵母膏0.5％、MgSO4·7H2O0.05％、K2HPO4 0.05％、黄浆水100％,pH为6.0,接种量10％。每250mL三角瓶装量100mL在30℃转速为200r/min的摇床振荡发酵培养,5～6d菌体生长量和曲酸产量最大。     

ISOLATION AND ANALYSIS OF A NOVEL ACIDIC POLYSACCHARIDE WITH GLUCOKINASE-STIMULATING ACTIVITY FROM COARSE GREEN TEA

Water‐soluble polysaccharides from coarse green tea were separated by anion‐exchange chromatography into five fractions (fraction A [FA], fraction B, fraction C [FC], fraction D and fraction E). Two of these fractions, FA and FC, contained significant glucokinase‐stimulating activity (P < 0.05). The major component, FC, showed the most activity, and thus, was further purified by gel filtration chromatography, thereby obtaining fraction C‐1 (FC‐1) and fraction C‐2 (FC‐2). The biological activity of the two fractions was investigated, and FC‐1 displayed higher glucokinase‐stimulating activity (P < 0.01). Chemical tests combined with IR and UV spectroscopy revealed that FC‐1 is an acidic polysaccharide without conjugation to protein. Sugars of FC‐1 are composed of rhamnose, arabinose, mannose, glucose and galactose in the ratio of 12.57:22.95:4.4:39.34:20.77. Uronic acid analysis by ion chromatography showed that FC‐1 contains 8% galacturonic acid, and its molecular weight was estimated to be approximately 6 × 10⁴ using a Sephacryl S200 column. These results are different from the observations previously reported, therefore suggesting that FC‐1 is a novel polysaccharide.     

茶多酚的应用及提取方法

茶多酚是一种天然的抗氧化剂,在食品加工、医药、日用化工等领域具有重要的应用.主要介绍了茶多酚的组成、性质及应用并对它主要的提取方法作了简要介绍.     

应用二次回归正交旋转组合设计优化五倍子多糖提取工艺

考察时间、温度、料液比、粉碎度及超声功率五个单因素对超声波提取五倍子多糖的影响，并采用二次回归正交旋转组合设计优化多糖提取率的最佳提取时间、料液比、超声功率条件的试验回归方程，确定超声波提取五倍子多糖的最佳工艺条件为：提取时间30min，料液比1：20，超声功率300W。