Effect of temperature and drying method on the phenolic profile of four varieties of figs (Ficus carica)
摘要
This work explores the impact of different drying techniques and temperature on the phenolic profiles of four fig varieties (Aberkane, Ghoudani, Taamrioute, and Tahiounte). Fresh figs and figs subjected to sun drying and oven drying at 50, 60, and 70 °C were analyzed for their phenolic compound composition using HPLC-(DAD)-MS. The analysis showed that fresh figs are rich in phenolic content and exhibit wide variation in composition, with twenty-three identified compounds, including four phenolic acids, five flavonols, and fourteen anthocyanin-derived compounds. Fresh figs exhibited the highest levels of most phenolics, particularly cyanidin 3-rutinoside (20.87–55.12 mg/100 g) and cinnamic acid (18.90–45.90 mg/100 g). The study of drying effects on major phenolic compounds revealed that sun drying and low-temperature oven drying (50 °C) were more effective at preserving these compounds, showing relatively low mean degradation rates (8–23%). In contrast, higher temperatures (60 and 70 °C) led to pronounced degradation, with total reductions ranging from 25% for the Aberkane variety to 36% for Taamrioute variety. Compounds such as trans-ρ-coumaric acid and quercetin 3-Ο-rutinoside were better preserved under sun drying and low-temperature conditions than at higher temperatures. Notably, anthocyanins were particularly heat-sensitive; for instance, cyanidin 3-glucoside declined from 12.01 (fresh) to 4.96 mg/100 g at 70 °C in Taamrioute, while cyanidin 3-rutinoside decreased from 53.82 to 30.54 mg/100 g in Aberkane. Oven drying at 70 °C resulted in consistent degradation across nearly all compounds and varieties. Multivariate analysis revealed varietal differences in phenolic stability, with dark-skinned varieties Aberkane and Ghoudani exhibiting greater retention of phenolic compounds compared to the lighter-skinned Taamrioute and Tahiounte. Thus, these results clearly demonstrate the need of choosing suitable drying methods and temperatures to preserve phenolic compounds of figs, with sun drying and low-temperature oven drying emerging as the most favorable options.