Effect of processing on phenolics of wines.

ABSTRACT

Phenolics of grapes are the main compounds responsible for color, taste, mouth feel, oxidation and other chemical reactions in wine and juice. Phenolic levels in wine and juice are affected by numerous processing conditions (crushing, pressing, sulfite addition, skin contact, oak aging). Studies were conducted to better understand the effect of processing on phenolic composition of three varieties of grapes. Three different processing steps: immediate press, hot press, and hull treatment (skin contact) for 7 and 14 days were applied to three different grape varieties, Vitis rotundifolia cv. Noble, Vitis vinifer cv. Cabernet Sauvignon, and the French-American hybrid Chambourcin. Phenolic compounds were identified and quantified by High Performance Liquid Chromatography (HPLC) and bitterness/astringency were assessed using a trained sensory panel. V. rotundifolia wines had higher levels of epicatechin and gallic acid but lower caftaric acid and procyanidins compared to the other varieties and were more astringent and bitter. Processing treatment affected phenolics and color differently among the three varieties.