桑红茶发酵工艺条件优化及活性成分含量的动力学研究

Optimization of Technological Conditions for Mulberry-black-tea Fermentation and Kinetic Analysis of the Active Ingredients

采用普通红茶加工方法制作桑红茶,在单因素试验基础上,确定影响桑红茶发酵的因素桑叶成熟度、发酵温度、发酵时间以及发酵湿度的优化区间,再选择后3个因素进行三因素三水平正交试验优化获得最佳的发酵工艺参数。影响桑红茶发酵的因素排序为发酵温度、发酵时间以及发酵湿度,其最佳发酵工艺条件为:以顶芽下2-3叶位的新鲜桑叶为原料,发酵温度20℃,发酵时间3h,相对湿度90%。在此优化条件下,桑红茶的色泽乌润,汤色红亮,滋味回甘,综合品质最好。对桑红茶在发酵过程中活性成分含量的动力学特征分析表明,随着发酵时间的延长,其游离氨基酸和1-脱氧野尻霉素(DNJ)含量逐渐增加,而总黄酮和多酚类化合物含量逐渐减少,并且各种活性成分的配伍也更趋合理。

Mulberry-black-tea was prepared by following the processing method for making ordinary black tea. Based on single-factor tests, factors including mulberry leaf maturity, fermentation temperature, fermention time and fermentation humidity were investigated to explore their influence on mulberry-black-tea fermentation and to determine ranges of these factors for further optimization. Subsequently, the latter 3 factors were selected to run the orthogonal test with three factors and three levels to obtain the best fermentation technological parameters. The results showed that factors affecting mulberry-black-tea fermentation were in the order of fermentation temperature, fermentation time, and fermentation humidity. The optimum process conditions were fermentation temperature of 20℃, fermentation time of 3 h, and relative humidity of 90% when the 2nd to 3rd fresh mulberry leaves below the top buds were used as the raw material. Under these optimum conditions, the prepared mulberry-black-tea was in black bloom and glow, and had a pleasant sweet aftertaste, showing the best comprehensive quality. Kinetic analysis of active ingredient contents in the fermentation process revealed that, as the fermentation time was prolonged, contents of free amino acids and 1-deoxynojirimycin （DNJ） were increased gradually while those of total flavonoids and polyphenolic compounds were reduced gradually. Moreover, the compatibility of various ingredients became more favorable.