添加PVPP对绿茶汤色的影响及作用机理的研究

Research of effect and mechanism of infusion color of green tea by adding PVPP

通过添加不同浓度的PVPP,研究儿茶素和黄酮醇类化合物的变化及其对绿茶汤色的影响。实验发现,添加高浓度PVPP(1.0%以上),绿茶汤色度(a*、b*值)下降,并表现为稳定的浅色泽体系;而添加低浓度PVPP(0.5%以下),茶汤的色度b*值出现少量下降,幅度较高浓度添加量的缓慢,而且加剧了储存过程中色泽的褐变。究其原因,PVPP可以吸附绿茶汤中的呈色物质黄酮醇类化合物,从而使绿茶汤色逐渐淡化;同时,PVPP对茶汤中的儿茶素类物质吸附能力更大,吸附效果由大到小依次为酯型儿茶素、非酯型儿茶素;对黄酮醇苷的吸附效果依次为黄酮醇单糖苷、黄酮醇双糖苷、黄酮醇三糖苷;在储存过程中,在缺失儿茶素的条件下,加快了黄酮醇类物质的转化速度,其中的杨梅素最易转化,槲皮素次之,山奈素相对稳定;黄酮醇三糖苷较单糖苷稳定。

The effect of catechins and flanonols compounds on green tea infusion color were investigated by adding different concentration of PVPP.As observed,the green tea infusion color was close to be colorless and the light color system was stable with adding high concentration of PVPP（1.0%）,but the chroma values a and b of the green tea infusion color were slightly reduced with adding low concentration of PVPP（0.5%）,which further increased the color deterioration during the green tea infusion storage.Based on these observation data,it was suggested that the PVPP could adsorb flavonols,which were color compounds,to attenuate the green tea infusion color.Further studies showed that the catechins＇ adsorbility was stronger than flavonols＇ and the adsorbilty of catechins was proved to be：ester catechinsnon-ester catechins.While the adsorblity of flavonols was：single indicantdiglucosidetriglucoside.Additionally,the transform ability of flavonol-like compounds was proved to be：myricetinquercetinkaempferol in the absence of catechins during the green tea infusion storage,while flavonol triglucoside was more stable than monoglycoside.