Browsing by Author "Swiegers, Jan H."

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    Differential synthesis of fermentative aroma compounds of two related commercial wine yeast strains
    (ELSEVIER SCI LTD, 2009) Molina, Ana M.; Guadalupe, Victor; Varela, Cristian; Swiegers, Jan H.; Pretorius, Isak S.; Agosin, Eduardo
    The specific impact of the yeast strain on the wine flavour and aroma has not been well characterised yet because this effect is usually combined with other variables during the winemaking. In this study, the contribution to wine flavour of two Saccharomyces cerevisiae strains widely used in wine production, VIN13 and EC1118, was evaluated after fermentation at 15 degrees C. Chemical defined grape juice media fermented with the EC1118 strain showed higher solvent, fatty and pineapple aroma attributes, while that fermented with the VIN13 strain exhibited higher banana, fruity, yeasty and green attributes. Sensorial and chemical analyses evidenced that the production of flavour-active compounds is significantly affected by the yeast strain, as well as by the temperature of fermentation, as shown by comparing the former data with those from fermentations carried out at 28 degrees C under identical culture conditions. (C) 2009 Elsevier Ltd. All rights reserved.
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    Influence of wine fermentation temperature on the synthesis of yeast-derived volatile aroma compounds
    (2007) Molina, Ana M.; Swiegers, Jan H.; Varela, Cristian; Pretorius, Isak S.; Agosin, Eduardo
    The yeast Saccharomyces cerevisiae synthesises a variety of volatile aroma compounds during wine fermentation. In this study, the influence of fermentation temperature on (1) the production of yeast-derived aroma compounds and ( 2) the expression of genes involved in aroma compounds' metabolism (ADH1, PDC1, BAT1, BAT2, LEU2, ILV2, ATF1, ATF2, EHT1 and IAH1) was assessed, during the fermentation of a defined must at 15 and 28 C. Higher concentrations of compounds related to fresh and fruity aromas were found at 15 C, while higher concentrations of flowery related aroma compounds were found at 28 C. The formation rates of volatile aroma compounds varied according to growth stage. In addition, linear correlations between the increases in concentration of higher alcohol and their corresponding acetates were obtained. Genes presented different expression profiles at both temperatures, except ILV2, and those involved in common pathways were co-expressed (ADH1, PDC1 and BAT2; and ATF1, EHT1 and IAH1). These results demonstrate that the fermentation temperature plays an important role in the wine final aroma profile, and is therefore an important control parameter to fine-tune wine quality during winemaking.