Volatile and sensory profile of organic red wines produced by different selected autochthonous and commercial Saccharomyces cerevisiae strains
Introduction
Growing concern among consumers in developed countries regarding the health and the protection of the environment has increased the demand for organic food over the last decade (especially in Germany, the United Kingdom, Switzerland, New Zealand, Japan, and the United States). Among organic products, EU consumers have shown an increasing interest in organic wines. More and more new organically based wineries are being established and old traditional wineries are adding organic wine to their product lines [1].
Wine quality is influenced, in part, by the composition of the grape juice and by the microbial communities present during the fermentation process. Aroma is one of the main characteristics that determine a wine's quality and value. The aroma of wine is a unique mixture of volatile compounds originating from grapes (varietal aromas), secondary products formed during the wine fermentation (fermentative aromas) and aging (post-fermentative aromas) [2]. The volatile fraction of wine can be made up of more than 800 different compounds [3] with a wide concentration range varying from hundreds of mg L−1 to μg L−1 or ng L−1 levels [4]. This great variety of volatile compounds, with different polarities, volatilities and a wide range of concentrations, is responsible for the complexity of the wine's bouquet and ensures its specificity and character [5].
The particular importance of each compound to the final aroma is related to its odour perception threshold [4]. General approaches to identifying “important” or high impact odorants are based on odour activity values (OAVs) and the concentration/threshold ratio. Odorants with low OAVs, or low impact odorants (i.e. with typical values <1) are generally considered to be unimportant to the overall sensory perception [6].
However, Ryan et al. [6] hypothesise that compounds with low OAVs could play a critical role in characterizing the overall odour of a sample. Furthermore, other authors think that OAVs provide only a rough evaluation of the real contribution of each compound to the overall aroma. In fact, the volatility and the perception of aroma compounds are significantly affected by the basic chemical composition of the wine, which can both mask the odour impact of certain compounds present in concentrations above their detection thresholds and favour the detection of other molecules present in concentrations below theirs [7].
A vast number of volatile compounds are formed and modulated by yeast during alcoholic fermentation and significantly impact the flavour and overall quality of wines [8]. The volatile compounds synthesized by wine yeast include higher alcohols, medium- and long-chain volatile acids, acetate esters, ethyl esters and aldehydes among others [9], [10]. The capacity to form aroma depends not only on yeast species but also on the particular strain of the individual species [11]. Different strains of S. cerevisiae can produce significantly different flavour profiles when fermenting the same must. This is a consequence of both the differential ability of wine yeast strains to release varietal volatile compounds from grape precursors and the differential ability to synthesise de novo yeast-derived volatile compounds [12], [13], [14], [15]. Therefore, selecting the proper yeast strain can be critical for the development of the desired wine style [7]. For this reason, modern wine makers prefer to employ selected yeast strains. For the production of young wine, the wineries select yeast strains that produce both the high levels of the esters and acetates needed for the desirable fruity taste and the low levels of higher alcohols that contribute negatively to aroma [11]. Moreover, employing selected starter yeast cultures provides technological advantages such as guaranteeing that the must ferments in the correct way. On the other hand, the use of autochthonous yeast strains, besides promoting biodiversity, is rather preferable since they are better acclimated to the environmental conditions and assure the maintenance of the typical sensory properties of the wines of any given region.
The aim of this work is to select the best yeast strains among autochthonous and commercial to obtain organic wines with high organoleptic qualities.
Section snippets
Yeast strains and yeast implantation control
Five different strains of S. cerevisiae were tested; four autochthonous strains were compared with a commercial yeast strain frequently employed by the winery for the vinification of red wines. The commercial yeast was Excellence XR (XR) (Lamothe-Abiet, Bordeaux, France) and the autochthonous yeasts were coded as MY, NY, OY and AGY. The commercial yeast was selected in accordance with the winery's preferences and the autochthonous strains were isolated from the same cellar and the neighbouring
Yeast analysis and fermentation kinetics
Forty yeast strains were isolated from the fresh juice before yeast inoculation. According to PCR-RFLP of the 5.8S rDNA gene, 38 isolates corresponded to non-Saccharomyces strains, and the remainder to the Saccharomyces genus. Further analysis characterised the last strains as the commercial yeast Excellence XR, frequently used by the winery.
To determine the implantation of the inoculated yeast in each vat, samples at different fermentation stages were analyzed by mitochondrial DNA RFLP. Fig. 1
Conclusions
The concentrations of most of the volatile compounds were significantly influenced by the yeast strain. Furthermore, because the implantation percentage of the strain sown in each vat was 100%, we can say that each strain tested is responsible for the volatile profile of the resulting wine. The differences observed in the volatile composition of wines obtained from different yeast strains appear to be quantitative rather than qualitative.
The results obtained in the sensory analysis suggest that
Acknowledgement
The authors are grateful for the financial assistance of the Andalusian Government.
References (34)
- et al.
SPME-GC method as a tool to differentiate VOC profiles in Saccharomyces cerevisiae wine yeasts
Food Microbiol.
(2009) - et al.
The significance of low impact odorants in global odour perception
Trends Food Sci. Technol.
(2008) - et al.
Differential synthesis of fermentative aroma compounds of two related comercial wine yeast strains
Food Chem.
(2009) - et al.
Different commercial yeast strains affecting the volatile and sensory profile of cava base wine
Int. J. Food Microbiol.
(2008) - et al.
Amplification and direct sequencing of fungi ribosomal RNA genes for phylogenetics
- et al.
Optimization and validation of headspace sorptive extraction (HSSE) for the analysis of volatile compounds in vinegars
J. Chromatogr. A
(2008) - et al.
Yeast starter cultures affecting wine fermentation and volatile
Food Res. Int.
(2001) - et al.
Funtion of yeast species and strains in wine flavour
Int. J. Food Microbiol.
(2003) - et al.
Characteristics of wines fermented with different Saccharomyces cerevisiae strains isolated from the La Mancha region
Food Microbiol.
(1999) - et al.
The demand for organic wines and organic wine marketing
J. Environ. Prot. Ecol.
(2007)
Yeast and bacterial modulation of wine aroma and flavour
Aust. J. Grape Wine Res.
Volatile flavour of wine: correlation between instrumental analysis and sensory perception
Nahrung
Comparative study of the volatile composition in wines obtained from traditional vinification and from the Ganimede method
J. Sci. Food Agric.
Coinoculated fermentations using Saccharomyces yeasts affect the volatile composition and sensory properties of Vitis vinifera L. cv. Sauvignon Blanc wines
J. Agric. Food Chem.
Definitive evidence for the actual contribution of yeast in the transformation of neutral precursors of grape aromas
J. Agric. Food Chem.
Yeast and its importance to wine aroma—a review
S. Afr. J. Enol. Vitic.
Analyses of aroma components of Chardonnay wine fermented by different yeast strains
Food Technol. Biotechnol.
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