Effect of intermittent microwave vacuum concentration on quality parameters of apple juice and sour cherry nectar and mathematical modeling of concentration

Abstract

Abstract In this study, sour cherry nectar and apple juice were concentrated using thermal concentration (75, 80, and 85 °C), and intermittent microwave concentration (180, 300, and 450 W) under vacuum condition (at 250 mbar). Thirteen different mathematical models were used to describe the concentration kinetics of the samples. The Midilli model exhibited the best fit to all experimental data (R2 ≥ 0.9972; χ2 ≤ 1.6724; RMSE ≤ 1.2932). The concentration time was reduced with increasing microwave power (from 180 W to 450 W) and thermal vacuum concentration temperature (from 75 °C to 85 °C). In addition, the main quality parameters of the concentrates were comparatively investigated after reconstitution. Generally, major differences were not observed in the physicochemical properties of samples concentrated by thermal and microwave methods. Total phenolic content of the apple juice and sour cherry nectar samples were ranged between 209.87-216.67 mg/L and 571.00-588.57 mg/L, respectively. Fructose was the main sugar in both juices, followed by glucose and sucrose. The particle size of the juice samples increased with concentration processing.