Zero Order Degradation Rate of Vitamin C in Fresh Orange andStrawberry Juices without Any Preservatives during Storage

Fresh orange and strawberry are rich in vitamin C, which is an essensial nutrient to promote a healthy imunne system. Vitamin C is easily degraded through oxidation process into dehydroascorbic acid during storage. Therefore, it is important to study the factors influencing the degradation rate of vitamin C in fruit juices without any preservatives. The aims of this research were to study the kinetic degradation of vitamin C in fresh orange (concentrated and nonconcentrated) and strawberry juices during storage and how the temperature affects these kinetics. Fresh juices were stored at room, refrigerated and frozen temperature. The content of vitamin C in fresh juices were analyzed using direct iodometric titration. Kinetic study of vitamin C degradation for these juices were carried out under isothermal condition. The degradation rates of vitamin C in fresh fruit juices based on zero kinetic model were compared. At room temperature the degradation rates of vitamin C in strawberry juice were about ten times faster than those in the orange juice. At refrigerated temperature the degradation rates of vitamin C in orange and strawberry juices with sugar were twice lower than theirs without sugar addition.