Optimization of heat treatment and pH of red and white pear cactus [Opuntia ficus-indica (l.) mill.] fruit juice using response surface methodology

Abstract

The objectives of the study were to determine the effect of heating time and temperature and pH level on the quality of cactus pear juice and to optimize the thermal treatment conditions and the pH for best results using two (red and white) varieties. Response surface methodology was used to optimize the heat treatment conditions and the pH. The heating time and temperature and pH significantly (p<0.05) affected the ascorbic acid content, sensory attributes and microbial load. Using graphical optimization, the best combinations for the red prickly juice were 5.5 to 14 mins and 62°C to 82°C with pH of 5.2 or pH 3.3 to 5.0 and temperature of 62°C to 92°C for 15 mins. For white prickly juice, the optimal ranges were 18.7 to 22.6 mins and 83.9°C to 93.4°C with pH of 5.2 or pH of 3.2 to 5.0 and temperature 93.5°C to 108°C for 15 mins. Using numerical optimization, the optimal conditions were 19.2 mins, 100°C and pH of 4 with a desirability value of 0.774 and 22 mins, 100°C and pH of 3.6 with the desirability value of 0.865 for red and white prickly pear juice, respectively.