Optimization of the bioactive compounds content in raspberry during freeze-drying using response surface method

Abstract

The production of high-quality freeze-dried raspberry was studied by response surface method. Two independent variables, temperature (X1) and time (X2) were determined as the most important factors affecting the final product quality estimated by the responses: total phenol (Y1), total anthocyanin (Y2), vitamin C (Y3) and total bioactive compounds (Y4) content. A two-factor central composite design was used for freeze-drying experiments. The second order polynomial models obtained were found to be significant (p<0.05) for all responses. The statistical analysis of experimental data indicated that only quadratic time variable (X22) had significant (p<0.05) effect on all responses. The optimal conditions for all responses combined were found to be: -31 ?C and 35 h. The experimental values of all responses obtained under optimal conditions were in good agreement with predicted values which enables the use of the proposed mathematical models for optimization of investigated process.