Degradation of ascorbic acid in dried guava during storage

Abstract

Retention of ascorbic acid (vitamin C) in dried guava during storage was studied. The effects of storage temperature: 30°C, 40°C, 50°C and water activity (aw): 0.43, 0.75, 0.84, 0.97 were investigated. The degradation of ascorbic acid follows a pseudo-first-order reaction. The rate constant increased about four to six fold when storage condition was changed from aw=0.43-0.97. The rate constants and corresponding water activities are related by a second-order polynomial equation. The effect of temperature on the rate constant followed the Arrhenius relationship. The activation energy of ascorbic acid degradation is found to be in the range 3.4-11.0 kcal/mol. An empirical equation, based on temperature, water activity and rate constant, is developed to predict shelf life of dried guava in respect of ascorbic acid retention. © 2001 Elsevier Science Ltd. All rights reserved.