Effects of oven and microwave drying on phenolic contents and antioxidant activities in four apple cultivars

Fresh fruits can be preserved for later consumption using methods such as drying. However, fruit quality can significantly decline during processing. This study investigates the effects of microwave and oven processing on the preserved quality of dried apple. Heating experiments were performed at two different microwave output powers of 180 and 540 W. Moisture contents of 'Starking' and 'Pink Lady' apple samples dried in a microwave at 180 W were substantially lower than those of other apple cultivars and control groups. Total phenolic contents, 325.94 mg/100 g (Pink Lady) to 475.63 mg/100 g (Starking), and antioxidant activity levels, 325.94 mg/100 g (Pink Lady) to 475.63 mg/100 g (Starking), of apples subjected to microwave heating at 540 W were higher than those in apples subjected to 180 W microwave heating and oven drying at 50 and 70 °C. The total phenolic contents of control apple cultivars ranged from 87.81 mg/100 g (Golden) to 136.25 mg/100 g (Pink Lady), whilst the total phenolic contents of apple cultivars dried in an oven at 70 °C ranged from 299.06 mg/100 g (Pink Lady) to 395.31 mg/100 g (Starking). The antioxidant activity values of control apple cultivars ranged from 11.55 (Pink Lady) to 21.78% (Starking), whilst the antioxidant activity values of apple cultivars dried in a 70 °C oven ranged from 38.87 (Pink Lady) to 52.49% (Granny Smith).