The effects of hot water bath and steam pretreatments were investigated, considering color, anthocyanin profile and antioxidant activity of blueberry (Vaccinium ashei) juice. The juice maximum total phenolic content, anthocyanin, and antioxidant activity were observed using the steam pretreatment processing method. Eleven anthocyanins were isolated from the blueberry juice of steam treatment processing, while only 10 from the hot water bath and 8 from the control sample. After storage at 40°C for 10 days, the anthocyanin retention rate of the juice from steam treatment processing was higher than in that from hot water bath and control sample (30.71%, 23.77%, and 19.91%, respectively). The antioxidant capacity was also significantly higher and the hue angle (H°) was lower in the juice from steam pretreatment processing. Steam pretreatment process could prevent color deterioration, increase variety and content of anthocyanins, and improve antioxidant activity in the blueberry juice.

The aim of this study was to evaluate the influence of adding copigment gallic acid (GA) on the stability of anthocyanin and color in blueberry juice, and assays were carried out with different anthocyanin:GA molar ratios (1:0, 1:1, 1:3, 1:5) in accelerated experiments (40°C for 10 days). Results showed that the addition of GA made blueberry juice to appear more crimson color tonality, color saturation and anthocyanins stability. The most obvious hyperchromic effect appeared in juice with 1:5 of anthocyanin:GA molar ratios, and in this ratio, total anthocyanin content (137.67 mg/L) and main anthocyanin peonidin-3-glucoside content (51.68 mg/L) of the blueberry juice were higher than juice without copigment (total anthocyanin of 116.96 mg/L and peonidin-3-glucoside of 34.2 mg/L). Furthermore, anthocyanins in blueberry juice copigmented with molar ratios 1:5 of anthocyanin:GA were more stable at 4°C than that at 25°C and 40°C. Thus, the addition of gallic acid at appropriate levels might be a promising juice process technology to obtain juices with high color quality and anthocyanin stability.