Effects of Different Drying Methods on Nutritional Components, Antioxidant Activity and Volatile Components of Five Kinds of Dried Figs

Drying methods may cause changes in the color and texture of figs, accelerating the loss of nutrients. In this study, five fig varieties ('Boji red' 'Orphan' 'Zhongzi' 'Qingpi' and 'Xinjiang Zaohuang') were used as research subjects. The nutritional components, antioxidant activity, and volatile compounds of figs dried by hot air drying at 60 ℃ and vacuum freeze-drying were characterized using gas chromatography-mass spectrometry (GC-MS) combined with electronic nose technology. The results showed that the effects of drying methods on the nutritional components in five fig varieties were significantly different, with the 'Zhongzi' variety showing the least color change. Hot air drying increased the total acid content of the five fig varieties, with 'Boji red' and 'Orphan' showing the largest increase. The freeze-dried 'Xinjiang Zaohuang' exhibited superior antioxidant activity compared to its hot air-dried counterpart, with a 47.83% higher retention rate of total flavonoids and a significantly increased reducing power (P<0.05). The total phenolic content reached 44.82 mg GAE/g. The electronic nose results suggested a good overall discrimination. A total of 85 volatile compounds were detected across the five fig varieties, with 'Boji red' figs being the least affected by drying, predominantly containing aldehydes. After hot air drying treatment, the ketones in control figs (in fresh, without any treatment) of 'Orphan' and 'Zhongzi' were converted into aldehydes (mainly benzaldehyde and hexanal). The ketones in hot air drying-treated figs of 'Qingpi' and 'Xinjiang Zaohuang' were converted into alcohols (primarily benzyl alcohol), which imparted a jasmine-like fragrance. In summary, vacuum freeze-drying-treated figs of 'Xinjiang Zaohuang' had the best retention of nutritional components and antioxidant activity, while volatile compounds of 'Boji red' figs were the least affected by drying methods. This study provides a scientific basis and reference for selecting appropriate drying methods and fig varieties for fig drying production.