3.3. Effects of sunlight exposure on SJ
Exposure to sunlight for 15 d caused the gradual fading of SJ color in glass bottles with or without BP. This result can be attributed to the strong penetrating power of sunlight at high temperatures. However, the fading rates of the samples without BP were more rapid than those of the samples with BP. The Ab510 of SJ with BP slightly decreased from 1.26 to 1.15 in 15 d, whereas that of SJ without BP decreased from 1.26 to 0.88. This result implies that sunlight can break down or transform the structures of anthocyanins.
Although the appearance of SJ without BP was worse than that of SJ with BP, L* slightly reduced in both types of samples without a significant difference ( Fig. 4). The results suggest that L* cannot reliably describe the fading of red color resulting from sunlight exposure.