Impact of Yeast Strain on Ester Levels and Fruity Aroma Persistence during Aging of Bordeaux Red Wines

The impact of yeast and lactic acid bacteria strains on the fruity aroma of red wines was investigated by sensory and analytical strategies. The ester composition of four different Bordeaux red wines was quantified by HS-SPME-GC/MS. These wines, made with selected yeast and bacteria strains, were investigated at the end of alcoholic fermentation and regularly until 12 months of aging, during 2011 and 2012 vintages. Sensory analyses of wines after 3 and 12 months of aging revealed significant differences with regard to yeast strains. Bacteria seemed to have only a slight impact on changes in aromatic profile. Ester levels were strongly influenced by yeast strain and very little affected by malolactic fermentation and aging. Differences and similarities between sensory data and ester profile are discussed. This study highlights the importance of yeast strains in red winemaking. Their sensory impact remains despite the other vinification steps after alcoholic fermentation

Control of plasmid-free strains.

<p>A. Comparison of NotI-PFGE patterns of plasmid containing strains (C9+, C10+) and isogenic plasmid-less derivatives (C9− and C10−). Red arrows indicate bands corresponding to plasmids in strains C9+ and C10+. B. Absence of plasmids in strains C9− and C10− was confirmed by multiplex PCR targeting a plasmid gene (ORF 20, 821-bp PCR product) and a chromosomal gene (<i>mleA</i>, 430-bp PCR product).</p

Comparison of growth in wine of isogenic strains with/without plasmids.

<p>Kinetics of alcoholic fermentation (CO₂ released, dark line), MLF (colored solid lines) and bacterial populations (colored dotted lines) were monitored in a sterile grape must inoculated with industrial wine yeasts and 10³.ml⁻¹ bacteria carrying pOENI-1 or pOENI-1v2 (red lines), bacteria without plasmids (blue lines) or a mixture of both (green lines). Kinetics of AF (dark symbols) is the mean of the three experiments.</p

<i>O. oeni</i> strains used in this study.

a<p>IOEB: Institute of oenology of Bordeaux, S: SARCO, ATCC: American type culture collection.</p

Genetic organization of pOENI-1 and comparison with related sequences.

<p>A. Genetic organization of plasmid pOENI-1. ORFs are represented by numbered arrows and identified by corresponding protein tags (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049082#pone-0049082-t003" target="_blank">Table 3</a>). B. Sequence comparison of pOENI-1 and related plasmids p1 (CP000424) and pH10 (CP002430). ORFs “c, d” (purple arrows) share 99% similarity with ORFs of pOENI-1v2. C. Portions of chromosomes in <i>O. oeni</i> ATCC BAA 1163 and <i>O. oeni</i> PSU1. The gene OEOE_0812 in <i>O. oeni</i> PSU1 (green arrow) is disrupted in <i>O. oeni</i> ATCC BAA 1163 by an 10 genes insert comprising four genes conserved in pOENI-1 (red arrows) and six genes unrelated to pOENI-1 (pink arrows). The insert is bordered by an 8-bp repeated sequence (dark triangles). D. Genetic organization of pOENI-1v2. ORFs numbered from 1 to 20 share more than 99% nucleotide sequence similarity with corresponding ORFs in pOENI-1. ORFs shaded in purple are not detected in pOENI-1 and code for transposases (a, e, f,), hypothetical proteins (b, c) and a recombinase (d). Pseudogenes are symbolized by arrowheads containing the symbol ψ. Regions of sequence similarity are indicated in percentages and shaded in blue. ori: putative origin of replication.</p

Distribution of pOENI-1 genes in 44 <i>O. oeni</i> strains.

<p>The dendrogram was constructed from DNA banding patterns obtained by NotI-PFGE analysis of 44 <i>O. oeni</i> strains. <i>Oenococcus kitaharae</i> was used as outgroup. Strain S11 was positioned on the basis of MLST data since no NotI-PFGE pattern was obtained for this strain. The presence (filled square) or absence (empty squares) of plasmid genes <i>repA</i>, <i>tauE</i>, <i>oye</i> and of the chromosomal gene OEOE_0812 were determined by PCR. The presence/absence of a region encompassing the <i>oye</i> and <i>parB</i> genes was also investigated. IOEB: Institute of oenology of Bordeaux, S: SARCO, ATCC: American type culture collection. Indutrial strains are marked with asterisks. Letters A and B in the dendrogram represent two phylogenetic groups of strains <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049082#pone.0049082-Bilhere1" target="_blank">[36]</a>.</p

Percentage of plasmid-carrying/plasmid-free cells at different times of winemaking.

a<p>strains inoculated in must.</p

Primers list.

a<p>Primers used in qPCR assays.</p>b<p>Product sizes obtained for pOENI-1 and pOENI-1v2.</p

Comparison of MLF kinetics of isogenic strains with/without plasmids.

<p>Kinetics of L-malate conversion (solid lines) and monitoring of cell population (dotted lines) were monitored following inoculation of bacteria to 10⁷ cells ml⁻¹ in a red wine containing 3 g l⁻¹ L-malate. A control was performed without added bacteria. Values are means of two biological replicates.</p

PCR detection of pOENI-1 and related plasmids in wines.

<p>PCR assays were performed using DNA templates from <i>O. oeni</i> C9 (pOENI-1), <i>O. oeni</i> S11 (pOENI-1v2) and 30 samples of wine collected during MLF (A–E). The number of samples sharing the same PCR product is indicated in parentheses. The primers allowed detection of pOENI-1 <i>repA</i> (panel A), <i>tauE</i> (panel B) and a region extending from ORF11 (<i>oye</i>) to ORF 13 (<i>parB</i>) (panel C). M: DNA size markers.</p