Effect of Ultrasound-Assisted Convective Drying on the Content of Bioactive Compounds and Drying Rate of Strawberry Slices

The strawberry is the most widely consumed berry in Europe, with a high content of minerals and bioactive compounds. During drying, the bioactive compounds are concentrated, but also partially degraded due to the interaction of high temperature and oxygen, among other factors. In this study, the effect of ultrasound support during the drying of strawberry slices of two cultivars, ‘Florence’ and ‘Alba’, was investigated. The effect of ultrasound application on the rate of drying, the retention of phenolic compounds and ascorbic acid, as well as the total colour difference, was measured. The time of ultrasonic-assisted drying was shorter than unassisted drying for the ‘Florence’ and ‘Alba’ cultivars, respectively, 35.7% and 34.6%. In addition, the dried product obtained with ultrasound had comparable antioxidant activity and polyphenol content. It was also shown that ultrasound can be successfully used in convective dryers without major equipment modifications.