Response Surface Modeling for Optimization of Textural and Color Characteristics of Dried Grapes

Abstract

Abstract This study presents the optimization of pre-drying treatment and storage conditions on textural and color properties of dried grapes using a response surface methodology – central composite rotatable design. Effects of three variables, potassium carbonate concentration (K2CO3, 5.98–11.02%), storage temperature (3.18–36.82°C), and relative humidity (RH, 6.96–91.04%), were evaluated. The response variables were defined as the rupture force, deformation, and Hunter L, a, and b values of dried grapes. Second-order empirical relationships with high R2 (>0.96) values between the responses and independent variables were derived. Results also showed that the K2CO3 concentration and temperature were the most significant factors influencing the studied textural and color characteristics, respectively. The overall optimum region resulted in the desirable characteristics was predicted at a combined level of 9.27% K2CO3 concentration, 4°C storage temperature, and 67.34% RH. Under these conditions, the corresponding predicted response values for the rupture force, deformation, and Hunter L, a, and b values of dried grapes were 2.15 N, 2.53 mm, 28.54, 3.25, and 9.74, respectively. The predicted values thus obtained were close to the actual values indicating suitability of the models.