Wild Strawberry Fragaria vesca L.: Kinetics of Fruit Drying and Quality Characteristics of the Dried Fruits

Abstract

The aim of this study was to determine the effect of the temperature of convection and freeze–drying of wild strawberry Fragaria vesca L. fruits on the drying kinetics and on selected quality features of the dried fruits. The process of convection drying was carried out at the temperatures of 25 °C, 40 °C, and 60 °C, whereas freeze–drying was carried out at the temperatures of 20 °C, 40 °C, and 60 °C of the heating shelves and at the pressure of 63 Pa in the lyophilizer chamber. The drying kinetics were best described by the Midilli model for both drying methods. An increase of the drying temperature to 60 °C, for both convection drying and freeze–drying, resulted in a decrease of the total content of phenolic compounds and of the antioxidant activity of the dried fruits. An increase in the temperature of convection drying reduced the lightness of the dried fruits. However, during freeze–drying, these features changed little despite the increase in the drying temperature. The dried fruits with the highest brightness were obtained at a freeze–drying temperature of 60 °C. The method of freeze–drying is proposed as the best because of the resulting color, L-ascorbic acid retention, and antioxidant properties of the dried fruits.