The Effect of Drying Temperature and Thickness on the Drying Kinetic, Antioxidant Activity, Phenolic Compounds, and Color Values of Apple Slices

Abstract

Dried fruit slices are important, healthy, and popular snacks and gain importance day by day due to their high nutritional content. In this context, this study mainly focused on the production of healthy apple chips snacks and the determination of degradation kinetics of antioxidant activity, total phenolic compounds, and color values of apple chip snacks during convective hot air drying at three different temperatures (45, 55, and 65°C) and sample thicknesses (1.5 and 5 ± 0.5 mm). The drying kinetics, desorption isotherms, activation energy, and half-life of the apple chip snack were also calculated. The Page and GAB models are the best models for the determination of the drying (>0.992) and desorption (>0.9979) behavior of apple snacks with the highest R2 values. The drying of all samples took place in the falling rate period. The Deff values increased depending on the increasing air temperature and slice thickness. The antioxidant activity, total phenolic compounds, and total color change of the 5 mm thick samples were degraded following the first-order reaction kinetics. The higher antioxidant activity, phenolic compounds, L∗ values, and lower half-life values were observed in conditions where the thickness (1.5 mm) and temperature (45°C) are low. The activation energy values calculated for the total phenolic compounds are higher than those calculated for the antioxidant activity. As a result, it can be concluded that apple chip snacks with high nutritional value can be produced by choosing low temperatures and slice thickness.