Effects of blanching on extraction and stability of anthocyanins from blueberry peel

Blueberry is rich in anthocyanins, but accounting for 98.2% of the total anthocyanins are in blueberry peel and difficult to release, due to the barrier effect of the cell wall, and the oxidation of polyphenol oxidase also lead to anthocyanins loss. The blanching has a desired effect on the blueberry cell wall and polyphenol oxidase. Therefore, the influences of blanching were studied. The results indicated that the total anthocyanin content of the pulp from the whole blueberry blanching was 1.3 times higher than that of the crushed pulp blanching, and the anthocyanin content obtained from the steam blanching was 0.19 mg/100 g more than the boiling water; the maximum value of 125.35 mg/100 g was reached at 2 min of steam blanching, and the polyphenol oxidase activity was reduced to less than 10%, steam blanching showed a good effect on anthocyanins extraction. Based on the optimal blanching condition, the pulp from blanched blueberries was less red and more blue than the non-blanched, due to the more of malvidin-glycosides and the addition of delphinidin-glycosides and petunidin-glycosides; the retention rate remained at 82% and the degradation rate remained around 1.09 after 40 days. This study could be proposed to apply on the blueberry pulp production for improving the anthocyanins extraction rate and stability.