Wine Quality Prediction from Juice Brix/Acid Ratio and Associated Compositional Changes for `White Riesling' and `Cabernet Sauvignon'

Abstract

General changes in the mineral and organic composition of must are shown. Total nitrogen, proline, phosphorus, and potassium increased with maturity. Ammonia and total acidity decreased, as expected. In the wine, phosphorus, potassium, proline, total nitrogen 2,3-butanediols, biotin, and alcohol increased. Total acids decreased (although not as much as in the musts), as did the tartrates and the extract for White Riesling. Generally, extract, tannin and color increased in the Cabernet Sauvignon with maturity. Amyl alcohol and total volatile ester changes were variable. Proline accounted for 70-80% of the total nitrogen in Cabernet Sauvignon wines. The quality of wine made from the Davis-grown grapes (when related to Brix/acid of the must) was highest at an intermediate maturity. The quality of wine from the Oakville grapes increased with maturity, with no significant decline for grapes of rather high Brix/acid ratio.