RESPONSE SURFACE OPTIMIZATION OF CONDITIONS FOR THE CLARIFICATION OF GUAVA FRUIT JUICE USING COMMERCIAL ENZYME

Abstract

ABSTRACT Response surface methodology was employed to optimize the incubation temperature (36.6–53.40C), incubation time (0.95–11.05 h) and enzyme concentration (0.16–0.84 mg/100 g guava pulp) on ascorbic acid retention, clarity, viscosity and color (L value) of guava juice. A central composite rotatable design was used. Significant regression models describing the changes of ascorbic acid, clarity, viscosity and color with respect to the independent variables (enzyme concentration, temperature and incubation time) were established with the coefficient of determination, R2, greater than 0.8. The results indicated that incubation temperature was the most significant (P < 0.01) variable in ascorbic acid retention, changes in clarity and color, whereas the incubation time showed the most significant (P < 0.01) effect on the viscosity of juice. The compromised optimum condition obtained by numerical integration for clarifying guava juice were: incubation temperature 45.35C, incubation time 7.23 h and enzyme concentration 0.70 mg/100 g guava pulp with ascorbic acid 77.71 mg/100 g, clarity 34.54% transmittance, viscosity 1.24 cps and color (L value) 23.33.PRACTICAL APPLICATIONSConsumption of natural fruit juice as an alternative to the traditional caffeine‐containing beverages such as coffee, tea or carbonated soft drinks has increased in recent years in Asian countries. Guava juice when extracted are mostly cloudy due to colloidal suspension and is needed to be clarified as clear juice is preferred. For increased juice yield, the fungal enzymes (pectinases) assist in pectin hydrolysis, causing a significant increase in juice yield. However, the effect of enzyme treatment on guava juice clarification has not been systematically studied. If the enzyme treatment also helps in juice clarification, it will be advantageous to the guava juice process industries. Therefore, the present study was aimed to optimize the hydrolysis pretreatment parameters (incubation temperature, time of treatment and enzyme concentration) for the maximal retention of ascorbic acid, clarity and color with minimal viscosity for the development of clarified guava juice for better acceptability of the product.