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

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, R-2, 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.