Abstract:
Abstract: Aiming to explore the effects of different fermentation temperatures on shape and liquor color index, theaflavins (TFs) and thearubigins (TRs), and the relationship among the indices, this article uses fresh Fuding Dabai tea leaves as raw materials, and sets 4 fermentation temperatures (25, 30, 35 and 40 ℃) to explore the dynamic change of shape brightness value (L value), shape redness value (a value), shape yellowness value (b value), and total color aberration value (△E value), total liquor color value (LC value), liquor brightness value (LL value), liquor redness value (La value) and liquor yellowness value (Lb value), as well as TFs, TRs and theabrownins (TBs), and the correlation among 3 kinds of indices is also discussed. The results show that, along with fermentation process, the shape color L value and b value decrease, and a value increases; liquor color LC value, La value and Lb value firstly increase, then decrease, and LL value decreases. The upheaval period of all the color properties occurs in the former 90 min, and the fluctuating or stable variation happens in the later 90 min. Comparison of different temperatures shows that, low temperature (20 or 30℃) is beneficial for the maintain of L, b, LC, Lb and La value, and meanwhile high temperature (35℃) is beneficial for the increase of a and LL value. The quality of the components TFs and TRs is increased firstly and then decreased, but TRs peak appears later than TFs, and the peak time and peak height are different due to different temperatures. On the whole, the formation and accumulation of TFs are the best at 25 ℃, TRs accumulation is the largest at 30℃, and 40℃ is the most suitable for formation of polymer TBs. The correlation analysis showed that there is significant positive correlation between TFs and TRs, and both TFs and TRs are extremely significantly positively correlated with TFRB (P<0.01), so the TFRB value is more effective than TFR value to represent the TFs and TRs contribution for tea quality. There is an extremely significant positive correlation among LC, La and Lb value (P<0.01), and the shape color attributes and liquor color attributes have a highly significant correlation: The shape color L and b values are negatively correlated with liquor color LC, La and Lb value (P<0.01), and positively correlated with the liquor color LL value. TFs is extremely significantly positively correlated (P<0.01) with L, b and Lb value, and has the strongest correlation with the b value, and is significantly positively correlated with the LC and La value. TRs is only significantly positively correlated (P<0.01) with a value and Lb value, and negatively correlated with L and b values. Through linear regression analysis, regression model of TFs is obtained using the LL, Lb and b value as variables, the R2 coefficient reaches 0.804, and regression model of TRs as the target value is not significant, so the model of TFRB value is established to explain the effects of TFs and TRs. Combined with the regression model of TFRB value, it can be seen that shape color b value is the most important among all the color indices, which is the key factor to judge suitability degree of fermentation and quality of TFs content.