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South African
Wine Lab Association:

Influence of Different Yeast Strains on Metabolism of Tryptophan and Indole-3-Acetic Acid during Fermentation

M. Mihaljevic Zulj*, I. Tomaz, L. Maslov Bandic, I. Puhelek, A.M. Jagatic Korenika, A. Heromel

The effect of supplementation of Riesling (Vitis vinifera L.) must with ammonium sulphate (AS) on
tryptophan (Trp) and indole-3-acetic acid (IAA) metabolism during alcoholic fermentation with four
commercial yeast strains (Uvaferm CEG, Lalvin Cross Evolution, Anchor VIN 13 and Anchor exotic
SPH) were examined.  AS addition reduced Trp uptake by yeasts from 1% to 15%. Wines produced by
Anchor VIN 13 and Uvaferm CEG yeasts with AS addition had the highest concentrations of Trp (0.60
and 0.59 mg/L respectively). Concentrations of total and bound IAA decreased during all treatments. At
the end of fermentation the highest concentration of free IAA was measured in the control must inoculated
with Anchor VIN 13 yeast (35.83 μg/L) and the lowest in the sample inoculated with Uvaferm CEG yeast
(13.08 μg/L). Anchor VIN 13 yeast showed the strongest change in metabolism due to AS addition during
fermentation. 2-Aminoacetophenone (2-AAP) formation was not observed in all the studied wines.

Ammonium sulphate, indole-3-acetic acid, tryptophan, untypical ageing off-flavour (UTA), yeast strain, 2-aminoacetophenone

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