FIELD OXIDATION

Post ripening and climate permitting, winegrowers will often hang their fruit on the vine to improve mouthfeel and concentrate flavors. When employed well, this technique can help achieve a phenolic balance in the vineyard that softens tannins, lowers reductive strength, and requires less “intervention” in the cellar. On the other hand, this technique decreases extractable anthocyanins, reduces a wine’s aging potential, and can oxidize fruit flavors. Grape quality during field oxidation is particularly fragile because the fruit is no longer safeguarded by the vine’s active metabolism. In a changing climate, this technique is best employed with caution and careful consideration.

From their peak, extractable anthocyanin concentrations steadily begin to fall. The amount they fall is subject to each vineyard, but it is common to see as much as 50% loss within three weeks post peak extractable anthocyanin accumulation. The rate of decay increases with temperature making the harvest decision a strong stylistic determiner. From a phenolic perspective, field oxidation lowers color potential, decreases tannin activity, and decreases phenolic reactivity. Bound anthocyanins do form in the vineyard (<50 ppm), but little in proportion to the amount formed during the first 100 days post-crush. Great wines of the world tend to have flavor ripeness that coincides with phenolic ripeness. These grapes tend to be abundant in flavor which integrates into structure as colloids form via bound anthocyanin polymerization.