Degradation of Cell Wall Polysaccharides during Traditional and Tank Fermentation of Chinese Liupao Tea

The
increase of polysaccharides in the dark tea pile process is
thought to be connected to the cell wall polysaccharides’ breakdown.
However, the relationship between tea polysaccharides (TPSs) and tea
cell wall polysaccharides has not been further explored. In this study,
the structural changes in the cell wall polysaccharides [e.g., cellulose,
hemicellulose (HC), and pectin] in Liupao tea were characterized before
and after traditional fermentation and tank fermentation. Additionally,
the degradation mechanism of tea cell wall polysaccharides during
fermentation was assessed. The results showed that cellulose crystallinity
decreased by 11.9–49.6% after fermentation. The molar ratio
of monosaccharides, such as arabinose, rhamnose, and glucose in HC,
was significantly reduced, and the molecular weight decreased. The
esterification degree and linearity of water-soluble pectin (WSP)
were reduced. TPS content increases during pile fermentation, which
may be due to HC degradation and the increase in WSP caused by cell
wall structure damage. Microorganisms were shown to be closely associated
with the degradation of cell wall polysaccharides during fermentation
according to correlation analyses. Traditional fermentation had a
greater effect on the cellulose structure, while tank fermentation
had a more noticeable impact on HC and WSP.

学界普遍认为，黑茶渥堆工序中多糖含量的提升，与细胞壁多糖的降解存在关联。然而，茶叶多糖（tea polysaccharides, TPSs）与茶叶细胞壁多糖之间的具体关联，尚未得到深入探究。本研究以六堡茶为对象，分别表征了传统发酵与罐式发酵前后，其细胞壁多糖（包括纤维素、半纤维素（hemicellulose, HC）及果胶）的结构变化；同时对发酵过程中茶叶细胞壁多糖的降解机制进行了评估。研究结果显示，发酵后纤维素的结晶度下降了11.9%~49.6%；半纤维素组分中阿拉伯糖、鼠李糖、葡萄糖等单糖的摩尔占比显著降低，且其分子量亦出现下降；水溶性果胶（water-soluble pectin, WSP）的酯化度与线性结构均有所降低。渥堆发酵过程中茶叶多糖含量升高，其成因可能为半纤维素降解，以及细胞壁结构受损所导致的水溶性果胶含量提升。相关性分析结果表明，发酵过程中的微生物与细胞壁多糖的降解存在紧密关联。传统发酵对纤维素结构的影响更为显著，而罐式发酵对半纤维素及水溶性果胶的作用效果更为突出。