Merlot, Cabernet franc, and Cabernet Sauvignon vines in Niagara-on-the-Lake, Ontario, were subjected to four treatments in a randomized complete block experiment: hedged control, cluster thinning at veraison (CT), basal leaf removal (BLR), and CT+BLR. Musts from each treatment replicate (CT+BLR excepted) were thereafter either left untreated or treated with either ColorPro or Color X enzymes. CT and CT+BLR treatments reduced yield per vine and crop load but had inconsistent effects on cluster weight, berries per cluster, and berry weight. BLR alone had few effects on yield components. CT and CT+BLR treatments generally had the highest soluble solids (Brix) in berries and musts and in most cases had the highest berry and must anthocyanin and phenol concentrations and color intensities (A420 + A520). Leaf removal resulted in slight increases in berry and must color intensity, anthocyanin and phenol concentrations, and little or no increase in Brix. CT and BLR both reduced titratable acidity (TA) and increased pH relative to the control, but BLR tended to be more effective than CT. BLR and CT+BLR treatments usually resulted in the lowest berry and must TA and the highest pH. Enzyme treatments increased must TA and reduced pH and typically increased color intensity, total anthocyanins, and phenols, but viticultural treatments generally had a greater magnitude of effect. The CT+BLR treatment has the potential to substantially improve fruit composition; negatively, excessive leaf removal could result in lowered Brix and TA and undesirable increases in pH. Enzyme treatment has the potential for increased color intensity, but with occasional increases in TA.
- © 2011 by the American Society for Enology and Viticulture