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In 2003 and 2004 vigor zones were delineated in two commercial vineyard
sites based on vine growth variation to assess fruit and wine phenolic chemistry. In
2004, the effects of shading on the accumulation of phenolic compounds were also
investigated. Model extractions were done from the shading experiment and the
vigor zones in 2004. Wine and extracts were analyzed by HPLC and
spectrophotometry.
Berry weight, dry skin weight, °Brix, pH and anthocyanin content were
higher and titratable acidity and the proportion of malvidin-3-O-glucoside was lower
in 2003 compared to 2004. High vigor zones had lower °Brix and higher titratable
acidity and a trend for lower anthocyanin content per berry in both years. Site A had
proportionally higher peonidin and lower malvidin than site B. While there were
minimal differences in seed proanthocyanidin, large increases were found in low
vigor zones for skin proanthocyanidin, proportion of (-)-epigallocatechin, and
pigmented polymer content in fruit. In 2004, the shade treatment had lower
accumulation of flavonols, lower skin proanthocyanidin, minimal differences in
anthocyanins, a large proportional increase in peonidin glucosides, and
proanthocyanidin compositional differences. The model extractions from the shade
experiment paralleled treatment differences in the fruit except that skin
proanthocyanidin percent extraction was found to be ~ 17% higher in the exposed
treatment.
For the vigor zone model extractions, there were no differences in pomace
weight. Site A model extracts tended to have a higher anthocyanin concentration and
a lower proportion of malvidin-3-O-glucoside than those from site B. The 2003
wines had a higher anthocyanin concentration and a lower proportion of malvidin-3-
O-glucoside than in 2004. The same response was seen in the fruit. The medium
vigor zone wines had higher anthocyanin concentrations than either high or low
vigor zones. In both years, there were higher proportions of delphinidin and
petunidin glucosides in wines made from low vigor zone fruit. Low vigor zone wines
had ~ a two-fold increase in pigmented polymer concentration, a large increase in the
proportion of skin proanthocyanidin, greater sulfite resistant pigments, higher color
density and lower flavan-3-ol monomer concentration. Differences found in the
wines magnified variation in the fruit. |
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