不同厌氧时间对绿茶和红茶加工品质的影响

Effect of Anaerobic Treatment Time on Quality of Green and Black Teas

以‘福鼎大白茶’、‘黄金芽’和‘白叶1号’的一芽二叶鲜叶为试验材料,采用不同厌氧时间(0、2、4、8 h)富集γ-氨基丁酸(GABA)的方式,结合绿茶和红茶工艺制备样品,探讨不同厌氧时间对绿茶与红茶工艺茶叶的GABA及主要品质成分的影响。结果表明,随厌氧时间延长,两种工艺茶叶的GABA含量均呈极显著增加趋势,游离氨基酸含量显著增加,茶多酚和水浸出物含量下降,咖啡碱含量变化不大。相同厌氧时间内,红茶工艺茶叶GABA富集量显著高于绿茶工艺茶叶,且高氨基酸茶树品种的GABA富集效果较好,黄金芽在绿茶和红茶工艺中GABA含量最高,分别为2.64 mg·g^(-1)、2.69 mg·g^(-1)。以厌氧温度为25℃、真空度为0.09 Mpa,厌氧时间为4 h的条件,分别结合杀青锅温为180℃,投叶量300 g,杀青时间为2min的绿茶工艺和以发酵温度为28℃,湿度为90%,发酵时间为4 h的红茶工艺,所制得的绿茶清香浓郁、滋味清爽,红茶香气高长、滋味醇厚,综合品质最佳,且达GABA茶标准。

The one bud and two fresh leaves from Fuding Dabaicha(Camellia sinensis),Huangjinya(Camellia sinensis),and Baiye 1(Camellia sinensis)plants were processed with different lengths of anaerobic treatment time(0,2,4,and 8 h)to encourage GABA formation in the tea products.The regular processes to produce green tea and black tea were followed to make different samples for this study.Contents of GABA and major chemical components in the tea samples made under the varied treatment times in a vacuumized chamber were compared.It was found that the experimental green and black teas had the contents of GABA and free amino acid significantly increased,tea polyphenols and water extract decreased,and caffeine changed slightly by prolonged anaerobic exposure.Under a same anaerobic treatment time,the black tea contained significantly more GABA than the green tea,and the enrichment was more pronounce in the cases where the leaves from high amino acid tea varieties were used as the raw material.For instance,Huangjinya had the highest GABA contents of 2.69 mg·g^(-1) in the anaerobically treated green tea and 2.64 mg·g^(-1) in the black tea.In the end,the treatment of 0.09 MPa vacuum at 25°C for 4 hours,either along with fixation at 180°C on raw leaves of 300g to blanch for 2 min making the green tea or a fermentation at 28°C with RH at 90%in processing the black tea,could render the most desirable products.The obtained green tea was judged to be richly fragrant with a refreshing taste,and the black tea long-lasting aromatic with a mellow flavor,while both met the standard on GABA content.