Oenological practices can affect the rate of extraction and final content of phenolic compounds in wine, e.g. by adding SO2.The moment of addition of SO2 can be very important for the final quality of the wine. In this paper the Authors investigated the effect of a delay SO2 addition during the early stages of vinification and after one year of storage on phenolic compounds. Grapes from Vitis vinifera var. Monastrell cultivated in Spain were harvested at optimum maturity. Two different lots (200 Kg each) were prepared. The first lot (W1) was crushed, destemmed and 5g/100 Kg of sodium metabisulfite was immediately added. The grapes of the second lot (W2) were treated the same way but sodium metabisulfite was added after 8 hours. Selected yeasts were added to both thanks of fermentation. Malolactic fermentation occurred in both wines. After cold stabilization the wines were bottled and samples were taken at the moment of bottling, and again, after 12 month of storage. Extraction, identification and quantification of phenolic compounds were made in triplicate. W2 showed more procyanidins, less hydroxycinnamic acid derivatives and less anthocyanins than W1. After 12 month of storage, in both wines the concentration of anthocyanins decreased. Flavan-3-ols also diminished with time, probably due to oxidation and polymerization. Total polyphenol level and ionized anthocyanins were higher in W1. The results show that the differences that already existed between both wines at the moment of bottling still exist after 12 months of storage. Delayed addition of SO2 does not remove the oxidation product that will enter coupled oxidation and condensation reactions, thereby changing the phenolic profile of wine.

Related sheets: