微波提取制备速溶茶及其品质影响因素

Preparation of instant tea by microwave extraction and a few factors on the quality

采用微波提取-超滤膜过滤-反渗透浓缩-真空冷冻干燥等工艺制备的速溶茶产品可以速溶于冷水,无“冷后浑”现象。提取三次后,产品的提取得率为干茶叶的25-30％。提取温度低于75℃,超滤膜PVDF和PVA,截留分子量为10万,冷冻干燥温度为-30℃。速溶茶产品中的大分子物质和金属离子含量,如蛋白质、胶质、钙离子等是形成茶絮凝的主要因素。速溶绿茶的蛋白含量高于20%,超滤残留物中的钙离子浓度达4862．68mg／kg,速溶茶中钙离子含量为541．94mg／kg。采用截留分子量10万的超滤膜过滤可以将部分大分子络和物除去,降低茶絮凝的形成机会,使速溶茶速溶于冷水,澄清透明。

Instant tea is manufactured by microwave extraction. And by filtration, membrane concentration and vacuum freezedrying, a new kind of tea powder which can be dissolved in cool water is prepared. The product yield is about 25-30% of dry tea leaf, after three times extraction. Different factors on the quality are studied in this work.. The extraction temperature is lower than 75℃, the filtration membrane is PVDF and PVA ,the inhibited molecule MW is about 105,the drying temperature is -30℃. The protein content of green tea powder is more than 20%. The protein, pectin and some ions are the main factors for the cream particles formation, especially the calcium ions, which may be combined with other big molecules and format particles. After filtration, the calcium ions can be separated from the tea solution. The Ca content in solid residue from filtration is about 4862.68mg/kg, and in tea powder is only 541.94mg/kg.