The impact of different factors (must protein treatment: bentonite and heat; pomace: fermented with and without; tannin addition: 0-9 g/L; and time of maceration: 0-11 days) on tannin, pigment, and protein extraction/retention in Frontenac wines was investigated. Wine tannin concentration and composition were determined by HPLC-fluorescence. Protein and pigment parameters were analysed by BCA assay and Boulton's method, respectively, using UV-spectrophotometry. Results: Bentonite and heat significantly reduced wine protein concentration at the end of alcoholic fermentation but heat was less efficient than bentonite (1.8-5.0 times less). Removing wine proteins did not improve tannin retention in wines (p > 0.1032) but fermenting without pomace significantly improved their retention (up to 2.4 times), especially that of polymeric flavan-3-ols (up to 27.8%). An addition of 3 g/L of enological tannins in wines, fermented with or without pomace, was necessary to increase wine tannin concentration significantly.
Keywords: Bentonite; Cold climate; Interspecific hybrid grape; Polyphenol; Pomace; Protein; Red winemaking; Thermovinification.
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