Effect of Vine Age, Dry Farming and Supplemental Irrigation on Color and Phenolic Extraction of cv. Zinfandel Wines from California

A dry-farmed vineyard block with vines of varying ages including young vines (5 to 12 years old), control vines (2:1 ratio of old to young vines), and old vines (40 to 60 years old) was either submitted to irrigation or dry-farmed. The experimental design yielded six treatments, namely, Irrigated Control, Irrigated Young, Irrigated Old, Dry-farmed Control, Dry-farmed Young, and Dry-farmed Old. Irrigated Young wines were lower in alcohol, anthocyanins, and tannins, as well as higher in pH and hue angle values (H*), than the remaining treatments. Dry-farmed Young wines were higher in anthocyanins and small polymeric pigments, and showed higher color saturation and red hue. However, the magnitude of these differences was small. At pressing, the anthocyanin composition of these Zinfandel wines was largely dominated by malvidin-3-glucoside (60 to 65%), but after 15 months of bottle aging their anthocyanin profile shifted to 60% of anthocyanin derivatives, with small polymeric pigments accounting for more than 70% of the total polymeric pigment content of the wines. Irrigated Old wines and Dry-farmed Old wines did not differ to any significant extent in their basic chemistry, phenolic chemistry (including detailed anthocyanin composition), and chromatic composition.