Phenolic Profile and Antioxidant Capacity of Skin-contact White Wines

Abstract

Background: Skin-contact white wines (also known as amber, orange, or macerated white wines) go through extended maceration during fermentation, giving the wine a characteristic amber- or orange-like color and a unique flavor. Objective: This study aimed to compare the polyphenolic profile and antioxidant capacity of selected skin-contact white wines from three different regions including the ones prepared with the traditional Kakhetian method. Methods: Samples consisted of nine commercially available skin-contact white wines from Greece, United States and Georgia. Wines from Georgia were prepared with the traditional Kakhetian method. Several physicochemical properties, total phenolic content (TPC), ß-carotene, and mineral content were determined. Results: TPC ranged from 447 to 2211 mg GAE/L, antioxidant capacity measured using ABTS and DPPH ranged from 643 – 2088 μmol TE/L, and 584 – 4421 μmol TE/L, respectively. Mn, Ca, Mg and P content ranged from 3.6 – 18.2 mg/L, 406 - 772 mg/L, 1530 – 2770 mg/L, and 530 – 2200 mg/L, respectively. A Principal Component Analysis (PCA) of the eight phenolic compounds that were present in more than one wine (gallic acid, vanillic acid, caffeic acid, caftaric acid, 4-CQA=4-Caffeoylquinic acid, p-coumaric acid, catechin, and epicatechin) identified two groups of skin-contact wines. Group one included the three amber wines from Georgia (samples 1 to 3) made following the Kakhetian method and one orange wine from the USA (sample 9). Group two included the remaining samples from the USA (samples 7,8) and the three samples from Greece (samples 4-6). Conclusion: Skin-contact white wines, despite having an extended maceration during fermentation in common, can be quite different in polyphenol content and antioxidant capacity, perhaps due to differences in the processing conditions.