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Polyphenol content and browning of Canadian icewines

Kilmartin, P.A., Reynolds, A.G., Pagay, V., Nurgel, C., Johnson, R.
Journal of food, agriculture & environment 2007 v.5 no.3-4 pp. 52-257
wines, oxidation, polyphenols, chemical composition, chemical concentration, coumaric acids, harvest date, absorbance, pH, freezing, air temperature, Ontario
The polyphenol composition of a range of Ontario icewines and late harvest wines was quantified. For 1999-2000 experimental wines, the FAUX icewines (harvested above -8°C and before 18 December) had high concentrations of hydroxycinnamates (10 to 37 mg/L in Riesling; 53 to 82 mg/ L in Vidal) which dropped to concentrations below 10 mg/L for the REAL icewines (harvested at temperatures -8°C or below and after 28 December). However, in 2002 experimental icewines, high concentrations of hydroxycinnamates were seen in both REAL and FAUX wines (40 to 84 mg/L in Riesling; 106 to 129 mg/L in Vidal), but all of the grapes were harvested before 11 December. Low to moderate concentrations of total hydroxycinnamates were observed in commercial icewines (10 to 40 mg/L) and late harvest wines (5 to 60 mg/L). Freeze concentration during icewine making appears to have substantial impact upon polyphenol composition and concentration, but time of harvest and growing season appear to be equally important.