温度对茶发酵叶色泽及茶色素含量的影响

Effect of temperature on color and tea pigment content of fermented tea leaves

为探究温度对发酵外形、汤色指标和品质成分的影响,并获得快速判别发酵适度的指标,该文以福鼎大白茶品种鲜叶为原料,设置25、30、35、40℃等4个发酵温度,首次检测在制品外形L值(亮度)、a值(红度)、b值(黄度)和△E值(总色差),汤色LC值(总汤色值)、LL值(汤色透亮度)、La值(汤色红度)和Lb值(汤色黄度)等色泽属性,以及TFs(茶黄素)、TRs(茶红素)和TBs(茶褐素)等品质成分的动态变化,建立3类指标的相关性。结果表明,发酵的进行会导致外形色泽L值、b值的下降,a值的增加,汤色LC值、La值和Lb值的先升后降,LL值的下降,各色泽属性的剧变期均发生在前90 min;不同温度比较,低温(25或30℃)有利于外形亮度L值、外形黄度b值、总汤色LC值、汤色黄度Lb值和汤色红度La的值的稳定,高温(35℃)有利于外形红度a值和汤色透亮度LL值的增加。品质成分TFs和TRs均呈先增后降的趋势,然茶红素峰值点出现时间晚于茶黄素,整体上以25℃发酵有利于TFs的形成和累积,而30℃发酵有利于TRs累积。相关性分析表明,TFs和TRs均与TFRB(茶黄素和茶红素之和与茶褐素的比值)呈极显著正相关,TFRB值较TFR值(茶红素与茶黄素的比值)更可有效代表茶黄素和茶红素在叶内的贡献表征;外形色泽属性与汤色色泽属性间呈极显著相关性,TFs与L值、b值、Lb值呈极显著正相关,与LC值、La值呈显著正相关,TRs仅与a值和Lb值呈显著正相关。通过线性回归分析获得了以LL值、Lb值和b值为变量的茶黄素回归模型,R2达到0.804,结合回归模型和相关性结果可以看出外形黄度b值最为关键,可作为判断发酵适度和衡量茶黄素含量的关键指标。

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 rawmaterials, and sets 4 fermentation temperatures （25, 30, 35 and 40 ℃） to explore the dynamic change of shape brightnessvalue （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 yellownessvalue （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 ofall 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, Lband La value, and meanwhile high temperature （35℃） is beneficial for the increase of a and LL value. The quality of thecomponents TFs and TRs is increased firstly and then decreased, but TRs peak appears later than TFs, and the peak time andpeak 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 correlationanalysis showed that there is significant positive correlation between TFs and TRs, and both TFs and TRs are extremelysignificantly positively correlated with TFRB （P〈0.01）, so the TFRB value is more effective than TFR value to represent theTFs 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 andb values are negatively correlated with liquor color LC, La and Lb value （P〈0.01）, and positively correlated with the liquorcolor LL value. TFs is extremely significantly positively correlated （P〈0.01） with L, b and Lb value, and has the strongestcorrelation with the b value, and is significantly positively correlated with the LC and La value. TRs is only significantlypositively correlated （P〈0.01） with a value and Lb value, and negatively correlated with L and b values. Through linearregression analysis, regression model of TFs is obtained using the LL, Lb and b value as variables, the R2 coefficient reaches0.804, and regression model of TRs as the target value is not significant, so the model of TFRB value is established to explainthe effects of TFs and TRs. Combined with the regression model of TFRB value, it can be seen that shape color b value is themost important among all the color indices, which is the key factor to judge suitability degree of fermentation and quality ofTFs content.