Effects of preconditioning on quality of dried blueberries

Abstract Blueberries are a rich source of phenolic compounds, especially anthocyanins, which contributes to their high level of antioxidant activity. However, these compounds of significant health benefit will be degraded after the blueberries undergo various air drying processes. Drying of blueberries can be difficult due to the wax layer surrounding the fruit. The health properties may be reduced to a large extent due to long exposure to high temperature. In this study, a mechanical wax abrasive pretreatment is used to carefully remove the wax layer and reduce drying time. The abrasive drum was lined with medium grain sand paper and attached to a constant speed rotator. The amount of blueberries and the rotating time were optimized to reduce the damage to the blueberries. Rabbiteye blueberries cv. Climax were used as the test fruit. A laboratory scale cabinet dryer was operated at temperatures between 50 and 90ºC with single stage and multistage drying strategies. The drying rates, colour and level of phenolic compounds and antioxidant activity were evaluated