STUDIES ON NONENZYMATIC BROWNING IN ORANGE JUICE USING A MODEL SYSTEM BASED ON FRESHLY SQUEEZED ORANGE JUICE

An orange juice based model system was set up wherein variables such as the addition of glucose, lysine, sorbitol and L‐ascorbic acid and changes in pH and storage temperature were introduced to study their effects on L‐ascorbic acid degradation and on browning. The addition of glucose, lysine and sorbitol did not have a significant effect on L‐ascorbic acid degradation, whereas added L‐ascorbic acid acted solely as a reserve material. In terms of browning, a change in pH and storage at elevated temperature produced a synergistic effect in the development of brown colour which was enhanced by the introduction of additives. Based on the results obtained, L‐ascorbic acid appears to be the precursor in the non‐enzymic browning occurring in this type of sample due to the formation of reactive carbonyl compounds produced upon its degradation which tend to polymerise, or to react with nitrogenous compounds, to give brown pigments. Copyright © 1990 John Wiley & Sons, Ltd