How to improve bayberry (Myrica rubra Sieb. et Zucc.) juice color quality:: Effect of juice processing on bayberry anthocyanins and polyphenolics

Fresh bayberries (Myrica rubra Sieb. et Zucc.) were processed into juice at an industrialized scale with four treatments: control, SO2 addition, pasteurization of the crushed pulp, and blanching before fruit crushing. Changes in anthocyanin pigments and polyphenolics (hydrobenzoic acids and flavonol glycosides) were monitored during processing. Centrifuged juice yield ranged from 73 to 78% (w/w), but only 12-27% of the anthocyanins and 20-32% of the polyphenolics were recovered in the ultrahigh-temperature (UHT) juices. Fifty-two to 58% of anthocyanins and 30-35% of polyphenolics were present in the centrifuged cakes. The initial processing steps of blanching, crushing, pasteurization, and depectinization caused a great loss of total and individual polyphenolics. Total monomeric anthocyanins were significantly higher (p < 0.05) in pasteurization- and blanching-treated samples than those in the SO2 treated samples, whereas those in the SO2-treated sample were significantly higher (p < 0.05) than those in the control juice. Overall polyphenolic levels were significantly higher (p < 0.05) in pasteurization- and blanching-treated samples than in the SO2-treated and control samples after each processing step. Important changes occurred in the polyphenolic profile with a 50-150% of hydroxybenzoic acids increase due to the free gallic acid from the flavonol glycoside-gallates during the initial processing steps. Flavonol deoxyhexosides were more stable than the flavonol hexosides during bayberry juice processing.