Several factors like vineyard site, climate, grape variety, ripeness, physical health of the grapes and pest management influence the populations of indigenous yeasts on grapes and later on in spontaneous fermentations. During spontaneous fermentations, so called “wild yeasts” could significantly influence the wine aroma. Some authors certify more complexity and an increase of wine quality to these fermentations. A widespread opinion is that spontaneous fermentation can help to emphasize the characteristics of a specific geographical area or even of one vineyard site.
This was checked in a three years experimental period testing different pest management strategies to replace or reduce copper and sulphur and comparing integrated, organic and biodynamic strategies. Alternatives to copper or sulphur treatments could however have an impact on the aroma profiles, as they alter the composition of natural yeast populations in the vineyard or lead to changes in yeast metabolism. This was tested with several alternative strategies compared to organic-standard and integrated variants. Effects on spontaneous flora, fermentation course and aroma profiles were analysed.
Yeast populations on grapes and at different stages of grape and must processing were isolated and determined using RFLP analysis of the ITS-region.
Hanseniaspora uvarum and Metschnikowia pulcherrima were the dominating species on the grapes in all variants. There was no correlation between the population dynamics of yeast during the processing and fermentation and the different pest management strategies.
In this survey the processing and the ecosystem winery seem to have a more important influence on yeast diversity than the microflora composition on grapes.
Authors: STÖLBEN T (1,2), RÜCK C (1,2), HERRBRUCK T (1,2), KAUER R (1), VON WALLBRUNN C (2)
(1) Fachbereich Geisenheim, Fachhochschule Wiesbaden, Von-Lade-Str. 1, 65366 Geisenheim
(2) Fachgebiet Mikrobiologie u. Biochemie, Forschungsanstalt Geisenheim, Von-Lade-Str. 1, 65366 Geisenheim
Keywords: yeast, spontaneous fermentation, organic pest management, RFLP, sensory analysis