Microwave-assisted drying of blueberry (Vaccinium corymbosum L.) fruits: Drying kinetics, polyphenols, anthocyanins, antioxidant capacity, colour and texture

Abstract

The aim of the study was to evaluate the effect of hot air convective drying (HACD), microwave vacuum drying (MWVD) and their combination (HACD+MWVD) on the drying kinetics, colour, total polyphenols, anthocyanins antioxidant capacity and texture of frozen/thawed blueberries. Drying resulted in reduction of total polyphenols content and antioxidant capacity (69 and 77%, respectively). The highest content of total polyphenols was noted after HACD at 90°C. Lower air temperature and prolonged exposure to oxygen resulted in greater degradation of polyphenols and antioxidant capacity. Drying processes caused a significant decrease (from 70 to 95%) in the content of anthocyanins. The highest content of anthocyanins and the strongest antioxidant capacity was found in blueberries dried using HACD at 90°C+MWVD. Among drying methods, HACD at 90°C+MWVD satisfied significant requirements for dried fruits i.e. short drying time and improved product quality.

Keywords: Antioxidant capacity; Colour; Microwave-assisted drying kinetics; Texture; Total monomeric anthocyanins; Total polyphenols; Vaccinium corymbosum.