An Investigation into the Degradation of Ascorbic Acid in Solutions

Accepted: 27/08/2014 Abstract The kinetics of the degradation of ascorbic acid (AA) in solution during heating at 30, 50, 70 and 90°C for 180 min and during 7 weeks of storage at 4°C and 20°C were investigated. The concentration of AA in solution was determined by the fluorimetric method before heating and storing the samples under different conditions. The retention of AA after heating at 30, 50, 70, and 90°C and storage at 4°C and 20°C was 87.6, 84.7, 73.8 and 43.6% (for heated samples) and 74.3 and 77.7% (for stored samples) respectively. Overall, there was a significant correlation (p<0.05) between the loss of AA as a result of heating of the samples or the storage of the samples at 4°C or 20°C. The degradation of AA in aqueous solution at each temperature was shown to follow a first-order kinetic model. The temperature-dependence of degradation was adequately modelled by the Arrhenius equation. The activation energy was 6.06 kcal/mole (for samples subjected to heat treatment) and 1.30 kcal/mole (for samples stored at 4°C and 20°C). The Q10 values were found to be 1.3 (for samples subjected to heat treatment) and 1.1 (for samples stored at 4°C and 20°C). The results from this study show that AA is a labile nutrient that can be easily lost during storage or processing. The results from this study contribute to the enhancement of the knowledge of the parameters that are of significance in the degradation of AA and thus provide an understanding of the conditions that can be used to optimize heat processing and storage of liquid foods that are rich in AA such as fruit juices.