Influence of the drying methods on color, vitamin C, anthocyanin, phenolic compounds, antioxidant activity, and in vitro bioaccessibility of blueberry fruits

Abstract

In this study, blueberry fruit was dried using different thin-layer drying methods, namely, natural drying, microwave drying, convective drying, and combined microwave-convective drying. The moisture content of blueberries initially at 84.76 +/- 0.20% w. b. was reduced to 10.03 +/- 0.09% w. b. Although the drying time ranged from 340 to 3540 min in convective drying, this period was completed between 64 and 198 min in microwave drying. Also, the natural drying period continued for 22 days. It was determined that the convective drying, which was completed for the longest time, also caused the most energy consumption compared to other drying methods.The color parameters closest to fresh blueberries were obtained at 50 degrees C, 70 degrees C, 90 degrees C at convective drying, and 300 and 500 W in microwave drying. The study concludes that blueberries show a high antioxidant capacity and comprise various amounts of polyphenols compounds. Moreover, for the total antioxidant capacity, CUPRAC is the most suitable method. The anthocyanin and vitamin C content also showed high values for blueberries. In general, it was determined that the best drying method in terms of color parameters, antioxidant capacity, anthocyanin content, and ascorbic acid content was the microwave drying method at 300 W with drying time at 82 min and 500 W with drying time at 64 min.