β‐glucosidase Activity in Juice‐Processing Enzymes Based on Anthocyanin Analysis

A screening procedure utilizing boysenberry juice as a substrate, which combined HPLC and spectrophotometric analyses, was used to measure β‐glucosidase activity of enzyme preparations used for juice processing. Enzyme preparations (n = 26) were evaluated at two dosage rates. At the mean recommended dosage, one preparation produced a decrease in total monomeric anthocyanin and cyanidin‐3‐glucoside, relative to a control, indicating β‐glucosidase activity. At 0.1% dosage, 4 enzymes produced a significant decrease in cyanidin‐3‐sophoroside and 2 enzymes caused an increase in cyanidin‐3‐rutinoside, indicating β‐1,2‐glucosidase activity. Such activity in juice processing enzymes was much lower and less prevalent than found previously for β‐galactosidase. Botrytis cinerea also degraded anthocyanins in boysenberry juice.