Changes in anthocyanins and polyphenolics during juice processing of highbush blueberries (Vaccinium corymbosum L.)

Frozen blueberries (Vaccinium corymbosum L,) were processed into juice and concentrate, and the changes in anthocyanin pigments and polyphenolics (cin namates, procyanidins, flavonol glycosides) were monitored. While juice yie ld was 83%, only 32% of the anthocyanins were recovered in single-strength juice. Flavonol, procyanidin and chlorogenic acid recoveries in juice were 35%, 43%, and 53%, respectively. The proportion of polyphenolics remaining in the press-cake residue ranged from 1% (chlorogenic acid) to 18% (anthocy anins). Pronounced losses of anthocyanins and polyphenolics during milling and depectinization are believed to be due to native polyphenol oxidase. Lo sses during concentration ranged from 1.5% (anthocyanins) to 20% (procyanid ins). Striking changes occurred in the anthocyanin profile with malvidin gl ycosides being most stable and delphinidin glycosides the least.