Dominik Durner,* Pascal Wegmann-Herr, Elena Diana Padureanu, and Ulrich Fischer
*DLR Rheinpfalz, Breitenweg 71, 67435 Neustadt, Germany (dominik.durner@dlr.rlp.de)

Much of the art of red winemaking is in controlling the extraction and development of grape phenolics. The objective of this study was to investigate the influence of berry ripeness on extraction of seed and skin polyphenols during fermentation/maceration of Pinot noir. Grapes with high and low ripeness were pressed gently and the pomaces of both ripeness stages were sorted into two fractions: skins and seeds. The obtained fractions were re-constituted in the juice in original and changed proportions. Analytical discrimination of seed and skin polyphenols was by LC-MS fingerprinting. During 14 days fermentation/maceration on low-ripe skins and low-ripe seeds, a disproportionate increase in seed polyphenols was observed. The wines were characterized by high content of gallic acid, procyanidin, procyanidin gallate, catechin, and epicatechin. Descriptive analysis of this wine revealed high bitterness, green tannin perception and low color intensity. Interestingly, the addition of high-ripe skins to the ferment could compensate for the negative impact of low-ripe seeds. Anthocyanin and prodelphinidin concentrations increased; procyanidins, catechin, and epicatechin concentrations were significantly lower when low-ripe seeds were combined with high-ripe skins. Wines from this artificial crossover were described as having high color intensity, low bitterness, and full-bodied, almost like wines made from high-ripe seeds. These observations suggest that higher berry ripeness particularly increases the extractability of skin polyphenols, and that skin polyphenols react with seed phenols. Similarly, the effect of 50% removal of low-ripe seeds was independent of skin ripeness; these wines generally showed poor color stability and green tannin impression, even in wines made from high-ripe skins. It is suggested that reactions between seed and skin polyphenols are crucial for color and mouthfeel of a Pinot noir and seeds are essential in red winemaking, even if berries are fully ripe.

Funding Support: Research Association of the German Food Industry (FEI)