STUDY OF NONENZYMATIC BROWNING DEVELOPMENT OF LOCAL SOUR ORANGE JUICE BY USING MODEL SYSTEMS 2-KINETIC STUDY OF ASCORBIC ACID DEGRADATION IN MODEL SYSTEMS OF LOCAL SOUR ORANGE JUICE DURING STORAGE.

Synthetic model systems of local sour orange juice prepared of concentrations 10,30 and 50%, with different contents of some compounds (ascorbic acid, glucose and amino acids) that might play a role in brown pigments formation. Samples were stored at 20, 30 and 40C for 4 months. Results of kinetic parameters of ascorbic acid degradation showed that the reaction order was first order, and the value of reaction constant (k) and degradation rate increased with increasing concentration of model system. The highest value of activation energy for ascorbic degradation was found in model system contained all compounds mentioned above and decreased with increasing concentration. Temperature coefficient (Q10) increased with increasing storage temperature ,The shelf life of model systems increased with increasing concentration and decreased with increasing storage temperature.