Effects of variable-temperature drying on nutritional components, antioxidant capacity, and flavor (volatile and non-volatile compounds) of Xinjiang figs

Abstract

A two-stage variable-temperature drying (VTD) process was optimized to improve the drying efficiency and quality of Xinjiang figs. The optimal conditions were 55 °C followed by 80 °C at a loading capacity of 2.73 g/dm2. Compared with constant-temperature drying at 60 °C, VTD shortened the drying time by 44.8%, reduced specific energy consumption by 20.4%, and decreased the browning degree by 22.8%. VTD also increased the retention of total phenolics, total flavonoids, and ascorbic acid by 17.59%, 27.78%, and 43.29%, respectively, resulting in higher antioxidant capacity. The summed semi-quantitative volatile abundance was higher in VTD than in CTD (39.78 versus 7.01 μg/g DW), mainly due to benzaldehyde and selected alcohols. Overall, two-stage VTD improved drying efficiency, nutrient retention, antioxidant capacity, and the volatile profile of dried figs, indicating its potential for further development of dried-fig processing under the tested conditions.