Changes in phenolics during storage of wine.

Red wine was prepared from Bangalore blue grapes (Vitis labrusca), and (i) 6 month old red wine and (ii) fresh red wine stored at 7 degree and 37 degree C for up to 10 wk. Samples were drawn from bottles every 2 wk, and analysed for phenolics and classified on the basis of their solubility in n-butanol or as non-soluble fractions. In (i) stored at 7 degree C, the ratio of total phenolics in aqueous fraction to butanol-soluble fraction increased from 1:0.4 to 1:0.58 whereas at 37 degree C over the 10 wk period there was an increase from 1:0.49 to 1:1.46. In (ii) stored at 7 degree C the ratio varied from 1:0.41 to 1:0.45, at 37 degree C the ratio increased from 1:0.45 to 1:3.20. Reduction and oxidation changes also proceeded at a faster rate at 37 degree C than at 7 degree C, resulting in degradation of wine colour from pink to brown.