Assessment of the effect of conventional and contemporary drying methods on the phenolic profile modulation and antioxidant retention of Trabzon persimmon (Diospyros kaki L.)

This study investigated the effects of conventional and modern drying methods on the total phenolic content, antioxidant activity, and phenolic compound composition of Trabzon persimmons (Diospyros kaki L.) fruits harvested from the same tree and at comparable maturity stages were subjected to sun drying, shade drying, oven drying, air-fryer drying, and microwave drying techniques, with raw samples serving as the control group. The total phenolic content was assessed via the Folin–Ciocalteu method, and the antioxidant capacity was evaluated using the ferric reducing antioxidant power (FRAP) and DPPH radical scavenging activity assays. The identification and quantification of phenolic compounds were conducted using the HPLC technique. The results indicated that the drying process produced statistically significant variations in the phenolic content and antioxidant capacity of Trabzon persimmons. The microwave drying technique resulted in highest total phenolic content and antioxidant activity, whereas both sun and shade drying procedures showed higher values than raw samples. The total phenolic content and antioxidant capacity of samples dried in an air fryer were found to be comparable to those of raw samples. The profile of phenolic compounds varied according to the drying process employed; certain compounds exhibited an increase with specific methods, while others were identified solely under particular conditions. Thus, it has been shown that drying techniques can have a significant impact on preserving and improving the functional properties of persimmons. Furthermore, we believe that microwave drying could be an effective alternative, particularly in terms of preserving bioactive compounds.