Effects of Hybrid Drying on Kinetics, Energy Analysis and Bioactive Properties of Sour Black Mulberry (Morus nigra L.)

Abstract

Due to the short harvest season and their sensitivity to storage, the preservation of fresh mulberry fruits is a very important process. Drying is a method used to preserve mulberry fruits in the long term. In this study, response surface methodology (RSM) was applied for the optimization of hybrid drying conditions of two different sour black mulberries. The linear and interaction effects of independent parameters such as temperature (50, 60 and 70°C) and microwave power (100, 200 and 300 W) variables were determined on mulberries. Bioactive properties and energy aspects were monitored as influenced by drying conditions. According to the results increase in microwave power provided a significant decrement in the specific energy consumption (SEC) and the total anthocyanin content (TAC), while increase in the energy efficiency (ηen) and total phenolic content (TPC) for both genotypes. In all cases, statistical values showed that all drying curves of black mulberry were best described by the Logistic model. Multiple response optimization was carried out for studied parameters and it was concluded that maximum antiradical activity (ARA), TPC, TAC, ηen and minimum drying time (DT) and SEC values would be at 300 W-50 ºC (desirability=0.842) and 300 W-66.5 ºC (desirability=0.744), for Morus nigra 1 (MN1) and Morus nigra 2 (MN2), respectively. According to the finding, the greatest TPC, ARA, TAC, DT, SEC and ηen were determined as 20.10 mg GAE/g, 86.00%, 456 mg/kg, 330 min, 18.59 kWh/kg and 9.04% for MN1, and 18.08 mg GAE/g, 83.92%, 835.81 mg/kg, 330 min, 16.16 kWh/kg and 10.40 % for MN2, respectively.