Objective Correlation between chlorophyll content of plucked leaves and fermentation in tea-making was analyzed to facilitate variety selection for processing black teas.

Method An SPAD-502 Plus chlorophyll meter was used to rapidly and non-destructively measure the relative chlorophyll contents of spring and summer new shoots on the tea bushes of 65 high-quality varieties (lines). One bud and two leaves plucked from the plants in the spring and summer were processed according to the standard fermentation procedure to make black tea samples. A regression analysis was conducted to examine the correlation between the SPAD measurements and fermentation performance of the leaves.

Result The durations required for optimal leaf fermentation significantly correlated with the SPAD readings on the first and second spring and summer new shoots on a tea plant with coefficients of 0.688, 0.665, 0.449, and 0.510, respectively (P＜0.01). The best-fit equation for the correlation on spring shoots was y = 0.1381x₁+ 0.0622 x₂+1.499, where x₁ refers to SPAD reading on the first spring shoots, and x₂, that on the second spring shoots. For summer shoots, it was y = 3.1913e^0.012x, where x is the measurement of second leaves. The spring shoot model carried low systematic errors, and the summer shoot model was accurate in predicting outcomes.

Conclusion In making black teas, fermentation performance closely related to the leaf SPAD measurements of the specific tea variety used as the raw material. The rapid, non-invasive method of using the chlorophyll meter employed by this study to obtain measurements on the leaves satisfactorily generated the data needed for selecting appropriate variety in breeding cultivars for producing quality black teas.