Effect of heat treatment on yeast inactivation, vitamin C and physicochemical quality of fresh pineapple juice

The effect of pasteurization-range heat treatment on yeast inactivation, vitamin C and the physicochemical characteristics of fresh pineapple juice were assessed. Yeast inactivation could be described by the Weibull model. The desired 6 log reduction was achieved at 63 and 65°C for 8 and 2 min, respectively. The pH, degree brix and organic acids did not change from 55 to 95°C. A significant change in fructose and glucose contents started to occur at 85°C, while sucrose hydrolysis was observed from 95°C. Likewise, hydroxymethylfurfural, one of the intermediate products of the Maillard reaction, was detected at 95°C.  Little degradation of ascorbic acid, the most important nutrient in pineapple juice- was observed. Hence, a mild heat treatment of 2 min at 65°C was sufficient to inactivate yeast and to preserve the nutritional and physicochemical quality of the pineapple juice.   Key words: Pineapple juice, heat treatment, yeast inactivation, physicochemical and nutritional quality.