Effects Of Strains And Physicochemical Conditions On Icewine Fermentation

This paper researched the effects of assimilable nitrogen concentration, yeast activator and yeast strains on Vidal icewine fermentation.A commercial nitrogen source(Thiazote? 250 ppm) was supplemented into ice grape juice to increase the initial assimilable nitrogen concentration.Then the ice grape juice was inoculated with a commercial Saccharomyces cerevisiae ST. The results showed that,supplement of nitrogen source promoted yeast growth, sugar consumption and the production of ethanol, acetic acid and aroma.The assimilable nitrogen concentration of synthetic ice grape juice was adjusted by adding diammonium phosphate(DAP) to 150, 250, 350 and 450 mg/L. The yeast growth,sugar consumption and metabolites were slightly affected by assimilable nitrogen concentration in the fermentation of the synthetic grape juice inoculated with ST yeast.For the fermentation of ice grape juice inoculated ST yeast activated by adding commercial yeast activator(Superstart? 300 ppm), the yeast growth could be significantly promoted at the beginning, and the formation of ethanol, glycerol and higher alcohols(over300mg/L) was increased, whereas acetic acid and esters were decreasedFive commercial wine strains Saccharomyces cerevisiae ST, VC, LV, RV and R were used in icewine fermentation respectively. The strains LV and RV showed greater cell growth and sugar consumption, more production of ethanol, glycerol and higher alcohols, low acetic acid. The strain VC consumed the least amount of sugar, produced lower contents of ethanol,glycerol and acetic acid, whereas more production of higher alcohols. The strains ST and R seemed to be close each other in some fermentation characteristics, consumed lesser sugar,produced the highest contents of acetic acid and moderate levels of ethanol and glycerol. In addition, the strain ST produced lower contents of higher alcohols and esters, the strain R produced lower contents of higher alcohols but higher contents of esters. The suitable yeast strain for Vidal icewine fermentation in this experiment was strain R, ST, VC, LV and RV in turn.During the ageing of Vidal icewine at 8-10 o C in sealed glass bottle, the contents of ethylacetate, diethyl succinate and 2-phenethyl alcohol increased gradually, however, the contents of acetic acid and other aroma reduced continually.