不同工艺条件对普洱茶渥堆过程中微生物及酶活的影响

运用实验室规模模拟渥堆，通过正交实验，研究不同工艺条件(初始水分含量、初始pH值和翻堆间隔)对普洱茶渥堆过程中微生物(霉菌)和酶活(多酚氧化酶、纤维素酶和果胶酶)的影响。结果表明：渥堆过程中，初期霉菌大量生长，随后趋于稳定。多酚氧化酶活性呈现增-减-增、先增后减和增-减-增-减3种变化趋势，纤维素酶和果胶酶酶活性呈现先增后减的变化趋势，仅酶活性峰值大小和出现时间不同。其中40~45%的初始水分含量能使茶胚渥堆过程中霉菌和各类酶活性维持在较高水平，调整茶胚的初始pH值对渥堆过程中微生物和酶活的影响不显著，翻堆间隔在8 d有利于茶胚霉菌保持在高水平，翻堆间隔在6 d有利于酶活保持在高水平。以茶褐素含量、茶多酚和儿茶素总量作为普洱茶氧化程度的指标，表明初始水分含量过高(50%)、翻堆间隔频率过高或过低(4 d、8 d)会引起普洱茶氧化过度，导致其品质下降。因此，选择合适的工艺条件有利于普洱茶品质提高。

Effect of Different Process Conditions on Microbes and Enzyme Activities during the Pile-fermentation of Pu-erh Tea

Effect of different process conditions on microbes (mould) and enzyme activities(polyphenol oxidase, cellulase and pectinase) during the pile-fermentation of Pu-erh tea was studied by orthogonal experiment in laboratory-scale. During pile-fermentation process, mould was growth in large number at the beginning then remained stable. Polyphenol oxidase exhibited 3 kinds of trends which were increase-less-increased, decreased after increasing and increase-less-increase-less. Cellulase and pectinase exhibited similar change trend that was decreased after increasing with various peak value and appearance time. In addition, mould and enzyme activities were remained at a high level by initial moisture content controlled in the range of 40% to 45%. There was no effect on mould and enzyme activities by pH modification. Mould was remained at a high level by turning intervals in 8 days and enzyme activities were remained at a high level by turning intervals in 6 days. Based on the contents of theabrownin, tea polyphenol and catechins, it indicated that Puerh tea would be excessive oxidation under high level initial moisture content (50%) and too high or too low turning interval frequency(4 d, 8 d). Therefore, proper process will benefit the quality improvement of Pu-erh tea.