The overall Ab510 of SJ varied greatly with pH. This value slightly varied when the pH was 3.0 and below. As the pH increased from 5.0 to 7.0, Ab510 decreased rapidly and almost no absorbance was detected at pH 7.0. As the pH from 7.0 to over 8.0, Ab510 abruptly increased to 2.3 (Fig. 2). The sensory transparency of the samples seriously decreased as the pH increased to 5.0 and above (Table 1), which greatly increased the readings on the spectrophotometer. Therefore, the decreasing or dramatic rising of Ab510 should not influence anthocyanin concentration. In addition, Ab510 should not
be used to indicate or calculate anthocyanin concentration when the pH is not at a suitable acid condition.