Isolation, characterisation, and selection of wine yeast strains in Etyek-Buda wine district, Hungary

Initiated by the Association “Wine Route of Etyek Wine District”, the objectives of this study were to isolate and identify autochthonous yeast strains from local wines and to determine their oenologically important properties. The first aim of this work was to characterize the taxonomic and phenotypic diversity of the representative Saccharomyces yeast strains that dominate the spontaneous fermentations in this wine district. The results obtained by molecular ribotyping (ARDRA) revealed a strong dominance of S. cerevisiae, but S. bayanus var. uvarum was also present sporadically. Some of the natural isolates exhibited high volatile acid production or poor fermentation capacity, which imply a quality risk in spontaneous fermentations. Most of the isolates, however, displayed good oenological features during lab scale fermentations. As the second aim of this work, the most promising, selected strains were further tested for oenological properties in microvinification scale and, finally, in large scale fermentations. The analytical and sensory analysis proved that selected strains, including S. bayanus var. uvarum, can be used as local starter cultures, which may contribute to the typicality of the local wines in comparison with commercial starters

On the complexity of the Saccharomyces bayanus taxon: hybridization and potential hybrid speciation

Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99¿100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains

Effect of three Saccharomyces cerevisiae strains on the volatile composition of albariño wines

Must obtained from Vitis vinifera L. cv Albariño grapes was inoculated with three strains of Saccharomyces cerevisiae (Asln1, Asln2 and Asln20) and fermented under identical conditions. Standard chemical analyses were carried out on the final wines and volatile compounds were analysed by gas chromatography. Statistical analysis of the data obtained by the latter technique showed that the wines produced differed depending on the yeast strain used. The formation of alcohols,esters and isoamyl acetate by Asln1, Asln2 and Asln20 differed significantly (P<0.05). The probability associated with the differences for isobutanol and isoamyl alcohol was 99.9%.Peer reviewe

Influence of Saccharomyces cerevisiae strains on general composition and sensorial properties of white wines made from Vitis vinifera cv. albariño

[EN] Yeast strains contribute to the oenological and sensorial characteristics of the wines they produce. The present study was performed to determine the influence of Saccharomyces cerevisiae strains on the composition and sensorial properties of Albariño wine. The must obtained from Albariño grapes was inoculated with 12 different yeast strains isolated from a single winery in Galicia, Spain. Chemical and sensorial analyses were performed on the final wines, which differed depending on the yeast strain used.[HR]Sojevi kvasca pridonose enolo{kim i senzorskim svojstvima vina. Istra`ivanje je provedeno da bi se odredio utjecaj sojeva S. cerevisiae na sastav i senzorska svojstva vina Albariño. Mo{t dobiven od gro`|a Albariño inokuliran je s 12 razli~itih sojeva kvasca izoliranih iz jedne {panjolske vinarije u Galiciji. Kemijska i senzorska analiza provedene su na dobivenim vinima, a rezultati su ovisili o upotrijebljenom soju kvasca.Peer Reviewe

Characterization of yeast strains from Rías Baixas (NW Spain) and their contribution to the fermentation of Albariño wine

The influence of different strains of Saccharomyces cerevisiae on the fermentation and sensory characteristics of wine was studied. Five strains were isolated from fermenting musts in the Rías Baixas region (NW Spain), and characterized by pulsed field gel electrophoresis. Each strain was assessed for pectinolytic and killer activity as well as for flocculation capacity. The strains were then used to ferment Albariño must on a laboratory scale. The wines produced, which showed significantly different (P<0.001) physicochemical parameters, were evaluated for aromatic quality by sensorial analyses. The wine obtained using one of the strains was given the highest rating by wine tasters, as its aroma was the most typical of the Rías Baixas wines.Peer Reviewe

Identificación genética de cepas de levadura del "Valle del Salnés" responsables de la fermentación espontánea del vino "Albariño"

5 páginas y 1 tabla.- Comunicación oral presentada en el Congreso celebrado en A Toxa (Pontevedra) entre los días 15 al 19 de mayo de 1994.El objetivo de este trabajo es precisar la heterogeneidad genética de cepas de Saccharomyces cerevisiae al curso de la fermentación espontánea de los vinos albariños de una bodega del "Valle del Salnés".Fundación Caixa GaliciaPeer reviewe

Hybrids <em>Saccharomyces cerevisiae</em> X <em>Saccharomyces bayanus</em> var. <em>uvarum</em> having a high liberating ability of some sulfur varietal aromas of <em>Vitis vinifera</em> Sauvignon blanc wines

We measured ability of some indigenous Saccharomyces bayanus var. uvarum wine yeasts to release volatile thiols from their S-cysteine conjugate precursors, odorous compounds responsible for the characteristic aroma of Sauvignon blanc wines. We also made interspecific hybrids between Saccharomyces cerevisiae and Saccharomyces bayanus var. uvarum strains and verified their hybrid origin with karyotypes and MET2 PCR-RFLP analysis. As compared to the parents, some hybrids could release high amounts of volatile thiols from the S-cysteine conjugate precursor without producing excessive amounts of β-phenylethyl alcohol and its acetate. One hybrid was retained for industrial production under a dry form and successfully compared with Saccharomyces cerevisiae strains in experimental tests in different cellars

Thiol precursors in Vitis mould-tolerant hybrid varieties

Background Over recent years, a new wave of disease‐tolerant to mildew varieties has flooded the viticulture sector, for reasons of human safety and economic expediency. These hybrid grape cultivars are selected mainly on the basis of their intrinsic capability to counter the attack of the main fungal diseases that affect grape production, such as downy mildew and powdery mildew. However, their organoleptic and enological characteristics have not yet been studied in depth for purposes of both juice and wine production, due to the high number of newly proposed germplasm and the lack of information about their adaptability to different environments. This work examines the thiol aroma precursors concentration in 64 red and white disease‐tolerant hybrid varieties in the vine germplasm collections of CREA‐VE and FEM, both from the north‐east of Italy. Results All cultivars showed the presence of 3‐mercaptohexan‐1‐ol (3MH) precursors, ranging from 4.4 to 1141 μg/kg for S‐glutathion‐3‐mercaptohexan‐1‐ol (GSH‐3MH), and 0.3 to 136 μg/kg for S‐cysteine‐3‐mercaptohexan‐1‐ol (Cys‐3MH). The concentration of GSH‐3MH exceeded 600 μg/kg in eight varieties, with values comparable with those of the richest V. vinifera reported so far. Red grapes showed, on average, higher concentrations of 3‐mercaptohexan‐1‐ol precursors than white ones. Only two hybrids had 4‐mercapto‐4‐methylpentan‐2‐one (4MMP) precursors over the limit of quantification, albeit with a much higher concentration than those normally reported in Sauvignon Blanc. Conclusion This is the first detailed survey of 3MH and 4MMP precursors carried out taking into account a considerable number of hybrid grape varieties. The results show that some of these varieties could be interesting for the production of tropical juices or tropical‐aromatic wines and soft drinks, through the enzymatic liberation of thiol aromas, as well as for the production of aromatizing tannins to be used in the food industr