Rates of vitamin C loss and discoloration in clear orange juice concentrate during storage at temperatures of 4-24degree C.

摘要

The rate of vitamin C degradation in clear orange juice concentrate produced by the combined membrane-evaporation technique was studied at storage temperatures of 4, 14, and 24鳦 for 19 weeks. Absorption at 420 nm and CIE L*, a*, b* colour parameters were determined to evaluate colour changes due to non-enzymic browning during storage. Calculated values of reaction rate constants indicated that vitamin C degradation occurred slowly in clear orange juice concentrate at 4鳦. Rates of vitamin C degradation ranged from 4.79 X 10-4 to 3.13 X 10-2 per week. The activation energy for vitamin C degradation was 34.3 kcal/g. mol. Main colour changes in stored clear orange juice concentrate in amber glass vials were due to increases in b* value and chroma.