Ascorbic acid destruction in sweet aqueous model systems

Abstract

The anaerobic destruction of L-ascorbic acid in sweet aqueous model systems (water activity = 0.94) of pH 3.5 was studied. Ascorbic acid degraded as a function of time and temperature with a behaviour that, in general, could be described by first order kinetics. The influence of the humectants tested (glucose, sucrose, sorbitol) on nutrient destruction depended on the temperature studied: at lower temperatures (24, 33 and 45 °C), humectants protected L-ascorbic acid from destruction, sugars being the most effective due to the structure-forming effect they have; at higher temperatures characteristic of processing (70, 80 and 90 °C), humectants with active carbonyls (glucose and sucrose) promoted ascorbic acid destruction, non-enzymic browning reactions probably being responsible for these results. The effect of sodium bisulphite presence was only significant at the lower temperature range producing inhibition of destruction; at higher temperatures the prevalence of nonenzymatic browning seemed to nullify the effect of this additive. It is concluded that not only water activity or additive effect but also solute-solvent interaction and other reactions taking place must be considered when analysing the effect of humectants and additives on ascorbic acid degradation. ©1997 Academic Press Limited.