Experimental design
Mixed level full factorial design (Montgomery, 2001 and Mason et al., 2003) was used in the experiments with four independent variables, viz. added sugar (X1), pressure (X2), temperature (X3) and treatment time (X4). Minimum of three levels of each factor was selected for obtaining second order polynomial equation. Three levels of sugar, pressure, temperature and four levels of treatment time ( Table 1) resulted in 108 (3 × 3 × 3 × 4) experiment combinations which were investigated for each enzyme. Levels of the independent variables were fixed according to the high pressure unit, literary information and operating conditions. Samples were treated in duplicate and analyzed in triplicates in all the cases (N = 2 × 3).