Color and Ascorbic Acid Degradation Kinetics of Red Pepper (Capsicum annuum L.) Slices during Vacuum Drying

Abstract

Red pepper slices were dried in a vacuum dryer at three different temperatures (45, 55 and 65°C) and two absolute pressures (21.5 kPa and 48.0 kPa). Drying temperature and absolute pressure significantly influenced drying time. Degradation kinetics of ascorbic acid in red pepper slices during vacuum drying followed a first-order kinetic model. The highest ascorbic acid retention occurred in the samples dried the combination of 45°C and 21.5 kPa. In addition to the temperature effect, the drying absolute pressure was effective on the loss of ascorbic acid. The activation energy values for ascorbic acid under both absolute pressure of 48.0 kPa and 21.5 kPa were calculated as 70.85 kJ/mol and 81.43 kJ/mol, respectively. The sample surface color degradation after drying was also determined. The color values (Hunter L, a and b) decreased, while ΔE (The color difference) increased during drying. Mathematical modeling of color degradation kinetics indicated that both the zero-order and first-order kinetic model were found to describe the Hunter L, a and b values. However, ΔE followed zero-order kinetic model.