A Review on Decaffeination of Tea Products

Since caffeine possesses some well-unknown adverse effects,many attempts have been conducted to remove it from tea products,including selective extraction with different solvents,enzymatic degradation and inhibition the caffeine synthesis pathway.Reports showed that caffeine can be safely and efficiently removed from fresh tea leaves by hot water blanching,however this approach is not suitable for treating the rolled or dried leaves because of the unavoidable loss of catechins.Although microwave-enhanced vacuum ice water extraction can be used for decaffeination of dried tea,time consumption seems to be the main shortage of this method.Liquefied dimethyl ether might be used as another alternative solvent for selective extraction of caffeine from tea products because of its low toxicity and residum,but its decaffeination efficiency needs to be verified furthermore.It has been proved that supercritical carbon dioxide extraction is an effective approach for removing caffeine from different types of tea products,while the application of the technique is always limited as its expensive equipments and high running costs.Decaffeination with microbe incubation or enzymatic digestion is highly hopeful since many studies showed that some microorganisms can degrade the caffeine through induced demethylase and oxidase under gentle condition in some model systems,unfortunately,this approach is far away from application since security and quality of the decaffeinated products are rarely concerned.Low-caffeine tea products can be easily produced through normal manufacture by using the leaves harvested from some low-caffeine cultivars which are derived through genetic modification or conventional breeding,but these germplasms are very limited.     

Enzymatic extraction of beta-glucan from oat bran cereals and oat crackers and optimization of viscosity measurement

The viscosity of the soluble fibre, β-glucan, has been shown to influence its ability to lower serum cholesterol and postprandial blood glucose levels. The impact of various amylases, proteases and lipase on the solubility and resulting viscosity of β-glucan extracted from oat bran cereals with a range of β-glucan concentrations and molecular weights was investigated. Addition of enzymes increased the final viscosity of high molecular weight β-glucan in cereals by facilitating the release of β-glucan from the food matrix. For cereals with partially depolymerized β-glucan, the addition of digestive enzymes decreased the final viscosity by eliminating the contribution of starch and protein to viscosity. Final viscosity varied depending on enzyme combinations including pancreatin, salivary and microbial α-amylases, microbial protease, porcine protease, trypsin and α-chymotrypsin. Addition of lipase did not significantly affect viscosity or solubility of β-glucan extracted from oat crackers. Addition of lichenase showed that β-glucan was the major contributor of viscosity to the system, with negligible interference from other components. The viscosity of the optimized protocol was compared to physiological results previously obtained. The viscosity of β-glucan extracted with pancreatin plus microbial α-amylase (pH 6.9) was predictive of LDL-cholesterol reduction (R² = 0.847) and glycemic response (R² = 0.883).     

油梨基因组DNA的提取及RAPD分析

用改进的ＳＤＳ法提取油梨基因组ＤＮＡ,即在细胞核被裂解之前,先去除细胞质中的酚类物质和蛋白质,然后用ＳＤＳ裂解细胞核,异丙醇和乙醇沉淀ＤＮＡ,成功地从油梨叶片中提取和纯化了ＤＮＡ。以１０个油梨品种的基因组ＤＮＡ为模板,４０个随机引物进行ＲＡＰＤ分析,结果表明,大部分引物可以在不同模板上扩增出条带,但仅有７个引物可以同时在１０个品种的油梨ＤＮＡ上扩增出条带;用ＲＡＰＤ结果对１０个油梨品种进行聚类分析,基本符合传统分类观点。     

牛瘤胃胃电频谱分析中窗函数的选择

采用三种常用的窗口函数,对牛瘤胃４ 种生理状态下胃电（峰电位和慢电位）的频谱进行了分析比较,得出了不同窗函数下频谱中幅值的特性,并分析确定了作者课题组频谱分析时的窗口函数——汉宁窗。     

籽粒苋鲜茎叶蛋白质含量及叶蛋白提取效率研究

对Ｋ１１２、Ｒ１０４等８个籽粒苋品种分不同时期进行了鲜茎叶蛋白含量分析和叶蛋白提取试验研究。结果表明,籽粒苋属于高蛋白质含量作物,全生育期叶蛋白含量平均达２８．７６％,采穗后茎叶平均蛋白质含量仍可达１１．１５％,其最佳利用时期为现蕾期至开花期,其中Ｒ１０４、Ｒ１０１１、Ｋ５７４蛋白质含量较高。     

富含多糖甜玉米幼穗RNA提取及高温胁迫基因表达分析

以改良Trizol试剂法从富含多糖的甜玉米幼穗中提取高质量、完整的总RNA,利用实时荧光定量PCR对高温胁迫下粤甜13雌穗发育的8个差异表达基因进行分析。结果表明,8个基因分为上调表达和下调表达,实时荧光定量PCR和测序法基因表达谱检测的基因上调或下调表达的趋势一致,上调表达基因ZM2G058057和下调表达基因ZM2G059964、ZM2G044670相对表达量较高,可能在高温胁迫影响甜玉米幼雌穗发育过程中起更重要的作用。     

大豆叶片蛋白质双向电泳技术的改良

以大豆叶片为材料,比较分析了3种蛋白质的提取方法,讨论了等电聚焦时间和染色方法等关键因素对双向电泳的影响,同时选择不同的IPG胶条,设定了第1向等电聚焦和第2向SDS-PAGE电泳的电泳程序及参数.结果表明:采用TCA-丙酮沉淀法提取蛋白质,选择pH 4 ～7( 17 cm) IPG胶条,适当延长和改变等电聚焦的第2步...     

虾类加工副产物制备虾青素的研究进展

文章介绍了从虾类加工副产物中提取和纯化虾青素的工艺技术.比较了不同前处理方式对虾青素提取效率的影响,并概括了高效液相色谱法和柱层析法纯化虾青素的相关技术.为天然虾青素的规模化生产提供理论依据.     

海参皂苷的分离提取与生物活性

海参具有较高的营养价值和药用价值.海参皂苷具有抗肿瘤,抗菌等多种生物活性,具有重大的应用价值和广阔的应用前景.本文对海参皂苷的提取、分离纯化、分析方法及生物活性进行初步的介绍.     

茶皂素的提取纯化及成品中茶皂素含量的测定

采用AB-8大孔吸附树脂对茶皂素成品进行纯化,提取标准品。利用紫外-可见分光光度计进行扫描得出茶皂素标准品在205nm处出现最大吸收峰;经香草醛-硫酸显色,最大吸收波长为435nm,在539nm处有较弱的吸收峰。用自制茶皂素纯品为标样,采用香草醛-浓硫酸显色法,绘制茶皂素定量的标准曲线,测定成品茶皂素的含量为80.9%。