Microwave-vacuum drying: Modeling validation of drying and rehydration kinetics, moisture diffusivity and physicochemical properties of dried dragon fruit slices

Abstract

This study investigated the drying of dragon fruit slices with varying samples (0.5 cm, 1 cm, and 1.5 cm) using a microwave-vacuum dryer at power levels of 400 W, 600 W, and 800 W, under a vacuum pressure of 600 mm Hg. The comprehensive assessment included drying kinetics, effective moisture diffusivity (Deff), rehydration behavior, color changes, and ascorbic acid content. Results indicated a substantial moisture content reduction from an initial 614.28% to an average of 7.14% (dry basis) post-microwave vacuum drying. The Wang and Singh model proved most suitable, exhibiting high R2 values and low RMSE values, providing accurate insights into the drying process. Dragon fruit samples showed Deff values from 4.381 × 10−3 to 4.084 × 10−2 cm2/min, increasing with microwave power level. Rehydration, modeled by the Peleg model, revealed that the highest power level had the highest R2 and lowest RMSE values. Notably, 1.5 cm slices at 400 W exhibited minimal color change (18.32) and retained the most ascorbic acid (6.94 mg/100 g). This study offers valuable insights into dragon fruit drying, highlighting its impact on moisture content, modeling, and product quality.