Authors: M Vilanova M Ugliano C Varela T Siebert I S Pretorius P A Henschke
Publish Date: 2007/09/11
Volume: 77, Issue: 1, Pages: 145-157
Abstract
Surveys conducted worldwide have shown that a significant proportion of grape musts are suboptimal for yeast nutrients especially assimilable nitrogen Nitrogen deficiencies are linked to slow and stuck fermentations and sulphidic offflavour formation Nitrogen supplementation of grape musts has become common practice however almost no information is available on the effects of nitrogen supplementation on wine flavour In this study the effect of ammonium supplementation of a synthetic medium over a wide range of nitrogen values on the production of volatile and nonvolatile compounds by two highnitrogendemand wine fermentation strains of Saccharomyces cerevisiae was determined To facilitate this investigation a simplified chemically defined medium that resembles the nutrient composition of grape juice was used Analysis of variance revealed that ammonium supplementation had significant effects on the concentration of residual sugar Lmalic acid acetic acid and glycerol but not the ethanol concentration While choice of yeast strain significantly affected half of the aroma compounds measured nitrogen concentrations affected 23 compounds including mediumchain alcohols and fatty acids and their esters Principal component analysis showed that branchedchain fatty acids and their esters were associated with low nitrogen concentrations whereas mediumchain fatty esters and acetic acid were associated with high nitrogen concentrationsWe thank Dr Paul Chambers for reviewing this manuscript This work was financially supported by grant from Galicia Government Xunta de Galicia Spain and by Australia’s grapegrowers and winemakers through their investment body the Grape and Wine Research and Development Corporation with matching funds from the Australian Government
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