Biodiversity of <em>Saccharomyces cerevisiae</em> Yeasts in Spontaneous Alcoholic Fermentations: Typical Cellar or Zone Strains?

Spontaneous fermentation is the most traditional way and a low-intervention method for conducting alcoholic fermentation in wineries, giving rise to the most complex wine profiles. However, inoculation with single culture inocula of Saccharomyces cerevisiae strains has become widespread in the modern wine industry. Nevertheless, some authors have pointed out that the use of the same yeasts in all the winegrowing regions of the world can cause a loss of typicity and have a standardizing effect on the wines. For this reason, many wineries and regions are carrying out programs of isolation and selection of yeasts that are typical of their vineyards/wineries. The aim of this work was to study the ecology of spontaneous fermentations in 11 wineries from all over the Rioja qualified designation of origin (Spain) during 3–4 consecutive years in order to establish the existence of typical strains belonging to wineries, sub-zones, or regional ecosystems. The results obtained showed a great diversity of strains of Saccharomyces cerevisiae in each fermentation studied. These strains were different each year in each winery, and hardly any common strains were detected between neighboring wineries, which would indicate that there are no representative strains from the winery or the area

Effect of the Sequential Inoculation of Non-Saccharomyces/Saccharomyces on the Anthocyans and Stilbenes Composition of Tempranillo Wines

The phenolic compounds of red wines are responsible for their color, astringency, and antioxidant properties. The fermentative yeasts might be used to modulate wines in terms of their color, aroma and probably healthy properties. In this study, six non-Saccharomyces species were tested because they might enhance the properties of red Tempranillo wines from Rioja. The results confirmed that the anthocyanins and stilbenes composition of wine can be modulated with the use of a specific fermentation starter. Metschnikowia pulcherrima, Zygosaccharomyces bailii, Candida zeylanoides, and Torulaspora delbrueckii achieved the greatest improvements of the monomeric anthocyanin composition, and the latter three yeast species achieved the best results of stilbene composition when compared to S. cerevisiae and the other non-Saccharomyces yeasts. Overall, results suggested that the use of M. pulcherrima, Z. bailii, C. zeylanoides and T. delbrueckii as fermentation starters could be of great interest to achieve wines with better color and likely healthy properties

Organoleptic characterization of wines in contact with oak wood fragments immersed in plasma activated water (PAW)

Oak barrels are a valuable material for wine ageing, although their difficult cleaning and disinfection favours microbiological contamination causing wine quality depreciation. Atmospheric pressure cold plasma is a suitable technique to reduce microbiota, but there is little research on its impact on the nutritional and sensory characteristics of foods. The aim of this study was to analyse the organoleptic characteristics of red wines in contact with plasma-activated waters (PAW) treated wood, of different origins and toasting levels. These red wines were compared with others that had been in contact with two types of control wood; some immersed in distilled water and others subjected to sulphur dioxide combustion. The results showed that oak wood treated with PAW did not cause defects at the olfactory and gustatory level of the red wines, which presented good harmony, sufficient body and balanced fruity and spicy notes, sometimes even superior to those described for red wines in contact with control wood (sulphited or submerged in distilled water). Therefore, the treatment of the wood with PAW did not have a negative impact on the sensory quality of the wines, regardless of the origin and toasting of the wood

Estudio del aire como vía de diseminación de microorganismos enológicos

El objetivo de esta tesis fue estudiar el efecto del aire como vía de diseminación de microorganismos enológicos, tanto en el viñedo como en la bodega, centrándose tanto en los agentes de las fermentaciones alcohólica y maloláctica, levaduras y bacterias lácticas, como en los mohos. Derivados de este estudio se publicaron tres artículos científicos. En el primero se estudió la presencia de mohos, levaduras y bacterias lácticas en el aire de una bodega durante la vinificación, y se compararon los clones de Saccharomyces cerevisiae aislados en el aire con los del mosto/vino de los depósitos en fermentación. Este artículo se completó con los resultados obtenidos acerca del estudio de las levaduras aisladas en diferentes zonas de las instalaciones de la misma bodega. En el segundo artículo se estudió el aire como vía de diseminación de las bacterias lácticas responsables de la fermentación maloláctica, comparando asimismo los clones de Oenococcus oeni presentes en el aire y en los vinos. Por último, en el tercer artículo se presentan los resultados del estudio realizado sobre la presencia y evolución de los microorganismos de interés enológico en las uvas y en el aire del viñedo durante el periodo de maduración en dos campañas consecutivas. Los resultados obtenidos indican que la presencia en el aire de los distintos tipos de microorganismos asociados a la uva y a la vinificación está directamente relacionada con los procesos enológicos que se desarrollan en la bodega. Además se observó que los microorganismos cuantitativamente más abundantes en el aire tanto en bodega como en viñedo fueron los mohos, y que dentro de las levaduras, las No-Saccharomyces son las mayoritarias en el aire del viñedo, la superficie de las bayas, las instalaciones de la bodega y también en el ambiente de la bodega antes de iniciarse los procesos fermentativos. Sin embargo, durante el desarrollo de las fermentaciones alcohólicas las levaduras encontradas en el aire de las bodegas pertenecen a la especie S. cerevisiae, debido a su proyección desde los depósitos, como lo prueba el hecho de que se encontraran clones comunes en ambos medios. Por su parte, la mayor proporción de bacterias lácticas en el aire de la bodega se produce cuando se están llevando a cabo las fermentaciones malolácticas. Además, en los momentos del proceso productivo en los que la uva o el vino se manipulan, los microorganismos que contienen pasan al aire y permanecen durante un tiempo en el ambiente para posteriormente depositarse, contaminando las superficies o el líquido sobre el que caen. Como conclusión del trabajo, se puede afirmar que la carga microbiológica del aire de la bodega es indicativa de los procesos que tienen lugar en ella y que existe un intercambio de microorganismos entre los tres medios: líquido (mosto/vino), sólido (instalaciones) y gaseoso (aire). Asimismo las manipulaciones del líquido son una fuente importante de proyección de microorganismos al ambiente. En el viñedo estas conclusiones no son tan claras. La técnica de análisis de la calidad microbiológica del aire que se ha utilizado en estos trabajos podría contribuir al control de procesos y desviaciones microbiológicas desde la maduración de la uva, pasando por la elaboración y conservación de los vinos

Yeast hulls: effect on spontaneous fermentation in different vinification conditions

The effect of the addition of yeast hulls in vinification was investigated during three consecutive years. The study was carried out in the experimental winery of C.I.D.A in La Rioja (Spain) with free running white grape juice of the Viura variety. Four different vinifications were studied. In two of these vinifications, stuck fermentations were detected. In all the studies, the addition of yeast hulls (yeast ghosts) improved the fermentation kinetics, increasing the number of viable yeasts at the end of the exponential stage and decreasing the final content of reducing sugars. This work revealed a new effect of yeast hull addition which had not been identified previously; their selection effect on the wild yeast strain in spontaneous fermentation

Selection process of a mixed inoculum of non-saccharomyces yeasts isolated in the D.O.Ca. Rioja

The use of non-Saccharomyces yeasts in sequential fermentations with S. cerevisiae has been proposed to improve the organoleptic characteristics involved in the quality of wine. The present study set out to select a non-Saccharomyces inoculum from the D.O.Ca. Rioja for use in winemaking. Strains included in the study belonged to Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, Zygosaccharomyces bailii, Williopsis pratensis, Debaryomyces hansenii, Pichia kluyveri, Sporidiobolus salmonicolor, Candida spp., Cryptococcus spp. and two mixed inocula of Lachancea thermotolerans-Torulaspora delbrueckii in a 30/70 ratio. In the first stage of the process, SO2 resistance and presence of enzymatic activities related to wine aroma and wine color and fining (esterase, esterase-lipase, lipase, leucine arylamidase, valine arylamidase, cystine arylamidase, β-glucosidase, pectinase, cellulose, xylanase and glucanase) were studied. In the later stages, selection criteria such as fermentative behavior, aroma compound production or influence on phenolic compounds were studied in laboratory scale vinifications. Taking into account the results obtained in the different stages of the process, a mixed inoculum of Lachancea thermotolerans-Torulaspora delbrueckii in a 30/70 ratio was finally selected. This inoculum stood out for its high implantation capacity, the production of compounds of interest such as glycerol and lactic acid and the consequent modulation of wine acidity. Given these characteristics, the selected inoculum is suitable for the production of quality wines