Comparative evaluation of the phenolic content and antioxidant capacity of sun-dried raisins

Raisins are one of the favorite dried fruit because of their high healthful and nutrimental values. Three white (Besni beyazi-BBR, Hatun parmagi-HPR and Sultaniye-SR) and two red (Antep karasi-AKR and Besni karasi-BKR) grape varieties were used in the present study. The aim of this study was to determine and compare the phenolic composition and antioxidant properties of Turkish raisins.

Four flavan-3-ols, six phenolic acids, four flavonols and 13 anthocyanins were identified and quantified in raisins. (+)-Catechin (range, 56.3-419 mg kg⁻¹) was the mosst abundant flavanol, trans-caftaric acid (range, 20.48-114 mg kg⁻¹) was the abundant dominannt phenol acid, quercetin-3-O-glucoside (range, 2.79-12.83 mg kg⁻¹) was the dominant flavonoll and malvidin-3-O-(6-O-p-coumaroyl)-glucoside (range, 16.75-22.59 mg kg⁻¹) wass the major anthocyanin in all raisins. Antioxidant capacity were 22.69-63.66, 5.07-40.47, 7.00-17.69 and 40.d 40.74-77.41 mmol Trolox kg⁻¹ as determined bby the ABTS, DPPH, FRAP and ORAC assays, respectively.

27 phenolic compounds from four phenolic families (i.e. flavan-3-ols, phenolic acids, flavonols and anthocyanins) have been characterised in the raisins of three white and two red grapes. The total phenolic and anthocyanins content vary widely among different raisins. Strong correlations between antioxidative capacity and phenolic content and between antioxidative capacity and flavonol content were noticed.