Impact of juice processing on blueberry anthocyanins and polyphenolics: Comparison of two pretreatments

Frozen blueberries (Vaccinium corymbosum L. cv. Rubel) were pilot-plant-processed into juice and concentrate: 2 treatments (heat and SO) and a control. Pressed juice yield ranged from 74 to 83% (w/w), but only 13 to 23% of the anthocyanins and 36 to 39% of the polyphenolics were recovered in the pasteurized juice. A substantial amount of anthocyanins and polyphenolics (> 42% and > 15%, respectively of the starting material) were present in the presscakes. Measurements of total and individual flavonoids showed a great loss after the initial processing steps (thawing, crushing, and depectinization). Overall anthocyanin levels were higher in treated samples after each processing step, but polyphenolic levels remained similar to those in the control.