Influence of Water Activity on the Nonenzymatic Browning of Apple Juice Concentrate during Storage

Highly concentrated clarified apple juice was kept in storage at 37°C over a period of 100 days. The soluble solids content ranged from 65–90.5°Brix. Color development was monitored as O.D. at 420 nm. A maximum nonenzymatic browning rate (NEB r ) was found to occur between water activities 0.53 and 0.55. It was assumed that (1) dilution of reactants was responsible for the browning rate reduction at high water contents white (2) viscosity inhibited the color formation at low water activities. Viscosity ranged from 48 to 1.3 × 10 6 cp and increased sharply when the commercial levels of concentration (70–72°Brix) were exceeded.