冷冻干燥对信阳毛尖品质的影响

Effect of Freeze Drying on the Quality of Xinyang Maojian

以信阳毛尖半成品(鲜叶→摊放→杀青→揉捻→排把)为原料,对其分别进行直接冷冻干燥、80℃电烘笼烘至含水量31%冷冻干燥、80℃电烘笼烘至含水量22%冷冻干燥,以80℃电烘笼直接烘干为对照,对样品进行感官审评和化学成分分析,探讨不同含水量初烘叶冷冻干燥对信阳毛尖干茶品质的影响。结果显示:(1)适当初烘后冷冻干燥干茶品质优于直接冷冻干燥和直接电烘笼烘干,其中,电烘笼初烘至含水量31%时再进行冷冻干燥的茶样感官品质最佳;(2)排把叶经初烘后再冷冻干燥,随着初烘时间延长含水量降低,其中水浸出物、氨基酸、可溶性糖含量先增高后降低,当含水量烘至31%时再冷冻干燥含量最高,与感官品质变化一致;而咖啡碱、叶绿素a、叶绿素b、叶绿素总量、简单儿茶素、酯型儿茶素、儿茶素总量随初烘叶含水量的降低其含量一直在降低,当初烘叶含水量22%时再冷冻干燥含量最低。

In this paper,Xinyang Maojian semi-finished products(tea fresh leaves→spreading→deenzyme→rolling→kneading)were used as raw materials that were subjected to direct freeze drying,freeze drying after 80℃electric oven drying to the water content of 31%,freeze drying after 80℃electric oven drying to the water content of 22%,respectively.The direct drying with 80℃electric oven as control.The sensory evaluation and chemical constituents analysis of the samples was carried out to explore the effect of freeze drying of primary drying leaves with different water content on the quality of Xinyang Maojian tea.The results show that:(1)The quality of dry tea after proper initial drying and then freeze drying was better than that of direct freeze drying and direct electric oven drying.Among,the sensory quality of tea samples that were freeze drying after initial drying in an electric oven to 31%water content was the best.(2)The kneading leaves after the initial drying was freeze dried,the water content decreased with the extension of the initial drying time,and the contents of water extracts,amino acids and soluble sugars increased first and then decreased.When the water content reached 31%after initial drying,these content of freeze drying sample was the highest,which was consistent with the change in sensory quality.However,the content of caffeine,chlorophyll a,chlorophyll b,total chlorophyll,non-ester catechins,ester catechins and total catechins had been decreasing with the decrease of the water content of the in intial drying leaves.When the water content of the initial drying leaves was dried to 22%,these content of freeze-drying sample was the lowest.