The Effect of Pasteurisation on the Microbiological and Nutritional Quality of Soursop (Annona muricata L.) Juice

The effect of pasteurisation on the nutritional and physicochemical quality of soursop juice was investigated. Soursop juice was prepared from soursop fruit pulp and pasteurised at different temperatures (63, 71, 78, 83 and 95°C) for different durations. The effect of pasteurisation on ascorbic acid level, total phenolic content and total antioxidant capacity of the juice was analysed. Additionally, the changes in pH, total soluble solids, titratable acidity and colour (L*a*b*) were determined. The pH, total soluble solids and titratable acidity were not significantly affected by pasteurisation. Pasteurisation affected the total phenolic content and total antioxidant capacity of the juice. For the same pasteurisation temperature, an increased duration of pasteurisation resulted in a reduction of total antioxidant capacity. Ascorbic acid levels in the juice decreased with increased duration and temperature of pasteurisation. A first-order kinetic model was developed to explain the effect of pasteurisation on the degradation of ascorbic acid in soursop juice. A degradation rate constant of 0.035 min-1 and an activation energy of 83 kJ/mol were obtained.