Reduction of 4-ethylphenol contents in red wines using HCDC+ yeasts and cinnamyl esterases

In this work we have studied the combined effect of using cinnamyl esterases (CE) and HCDC+ yeast strains of S. cerevisiae to transform TE-HCAs into vinylphenols to condense them with grape anthocyanins forming VPAs. These VPAs improve the color stability of the wine and at the same time remove EP precursors of the wine.

Influence of sequential and mixed fermentations with non-Saccharomyces yeasts on the sensory profile of red wine

The aim of this work is to evaluate the influence of S. pombe and T. delbrueckii species on the sensory quality of red wine when used in sequential and mixed fermentations with S. cerevisiae.

Identifying yeats belonging to the Brettanomyces/Dekkera genera through the use of selective-differential media

The purpose of this work was to compare and optimise different selective and differential media to aid in isolating spoilage yeasts belonging to the Brettanomyces/Dekkera genera. Growth media containing selective and differential factors were employed. These were inoculated with strains of yeast representing Spanish oenological microbiota. Lastly, some of these isolation media were successfully applied in 24 types of wine with a high ethylphenol content, all of which were from the Haro Oenological Station (La Rioja, Spain). p-coumaric acid was determined using High performance liquid chromatography-photodiode-array detection-electrospray ionization mass spectrometry (HPLC-DAD-ESI/MS); 4-ethylphenol by using Solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS); and the rest of the analysis was carried out using official OIV methodology. Actidione is the most effective selective factor for isolating Brettanomyces/Dekkera yeast genera. Other secondary selective factors (selective carbon sources, sorbic acid and ethanol as a microbicide agent) may be used successfully to eliminate potential false positivities; however, they slow growth and delay the time to obtain results.

Schizosaccharomyces selective differential media

This study discusses the optimisation of a selectiv e and differential medium which would facilitate the isolation of Schizosaccharomyces (a genus with a low incidence compared to other microorganisms) to select individuals from this genus for industrial purposes, especially in light of the recent approval of the use of yeasts from this genus in the wine industry by the International Organisation of Vine and Wine, or to detect the presence of such yeasts, for those many authors who consider them food spoilers. To this end, we studied various selective differential agents based on the main thephysiological characteristics of this species, such as its high resistance to high concentrations of sugar, sulfur dioxide, sorbic acid, benzoic acid, acetic acid or malo ethanolic fermentation. This selective medium is based on the resistance of the genus to the antibiotic actidione and its high resistance to inhibitory agents such as benzoic acid compared to possible microorganisms which can give rise to false positive results. Malic acid was used as a differential fact or due to the ability of this genus to metabolise it to ethanol, which allows detecting of the degradation of this compound. Lastly, the medium was successfully used to isolate strains of Schizosaccharomyces pombe from honey.

Hyperspectral images and polymerase chain reaction (PCR) for the detection of allergen (peanuts traces) in powder foods.

The addition of preservatives to some kind of foods may be a potential risk of spoilage, as it is the transformation of sorbate into the off-odour 1-3-pentadiene by certain microbial species. This is the case of the capacity of some strains of moulds and yeasts that are able to decarboxylate sorbic acid and transform it into 1-3 pentadiene, a volatile compound with an unpleasant petroleum odour. (Casas et al. 2004).

New Schizosaccharomyces applications in red wines alcoholic fermentation

The Schizosaccharomyces strains consumed less primary amino nitrogen and produced less urea and more pyruvic acid than other Saccharomyces species. Further, three of the four Schizosaccharomyces strains completed the breakdown of malic acid by day 4 of fermentation. The main negative effect of the use of Schizosaccharomyces was strong acetic acid production. The Schizosaccharomyces strains that produced most pyruvic acid (938 and 936) were associated with better ?wine? colour than the remaining yeasts. The studied Schizosaccharomyces could therefore be of oenological interest.

Optimización de parámetros fermentativos de calidad en vinos tintos de zonas cálidas

El aumento progresivo de la temperatura media anual y el déficit hídrico están provocando importantes cambios en la composición y la maduración de la uva, que repercuten directamente sobre el proceso fermentativo y, por ende, sobre la calidad del vino elaborado. En este trabajo se evalúan diferentes estrategias para la reducción del grado alcohólico, la mejora del color del vino y su estabilidad, y el incremento y la persistencia aromática. Mediante el empleo de levaduras con ineficiencia glicolítica se lograron reducciones medias en el grado alcohólico de entre 0.3 y 1.7 % v/v, mientras que con las fermentaciones secuenciales la máxima reducción lograda fue de 3.3 y 3.4 % v/v al combinar las cepas 938 (Schizosaccharomyces pombe) y 7013 (Torulaspora delbrueckii) con la 7VA (Saccharomyces cerevisiae). Al aplicar un tratamiento térmico sobre el inóculo, la TP2A(16) mostró una reducción media significativa en el grado alcohólico de 1 % v/v. El principal inconveniente en todas las técnicas empleadas para reducir el grado alcohólico fue la falta de repetibilidad en los resultados obtenidos. Por otra parte, la aplicación de altas presiones sobre uva despalillada resultó efectiva como tratamiento de pasteurización y como potenciador de la extracción de polifenoles, logrando un incremento en el contenido medio de antocianos totales del 12.4-18.5 %. La adición de flavonoides al mosto estimuló la formación de pigmentos estables como resultado de su condensación con antocianos mediada por acetaldehído. Con el empleo de Torulaspora delbrueckii en fermentación secuencial fue posible incrementar la producción de diacetilo y acetato de 2-feniletilo, además de la síntesis de un nuevo compuesto, el 3-etoxi-1-propanol. Sin embargo, su aportación sobre el color fue nula, así que debería combinarse con una cepa de Saccharomyces cerevisiae con buena formación de pigmentos piranoantociánicos. El empleo de Schizosaccharomyces pombe (938, V1) y Torulaspora delbrueckii (1880) en fermentaciones secuenciales y mixtas con Saccharomyces cerevisiae permitió mejorar el perfil sensorial del vino tinto mediante la mayor síntesis de polioles y la potenciación de aromas frutales, florales y herbáceos, e incrementar la estabilidad de la materia colorante al favorecer la formación de vitisinas y piranoantocianos vinilfenólicos. La crianza sobre lías en barrica a partir de levaduras seleccionadas, puede mejorar la complejidad y persistencia aromática del vino tinto, aunque sin grandes cambios en el color. ABSTRACT The progressive increase in annual average temperature, along with water deficit, is causing significant changes in grape composition and in its maturation, which directly affects the fermentative process and hence alters wine quality. In this work, different strategies for reducing the alcoholic strength, improve wine color and its stability, and increase aromatic complexity and its persistence, are evaluated. By using yeasts with glycolytic inefficiency, it was possible to achieve mean reductions between 0.3 and 1.7 % v/v in the alcoholic strength, while sequential fermentations allowed a maximum reduction of 3.3 and 3.4 % v/v by combining strains 938 (Schizosaccharomyces pombe) and 7013 (Torulaspora delbrueckii) with 7VA (Saccharomyces cerevisiae). When applying a heat shock treatment on the inoculum, only TP2A(16) strain showed a significant mean reduction of 1 % v/v in the alcohol content, compared with the control. The main drawback in all the techniques used to reduce the alcohol content was the lack of repeatability in the results. Moreover, the application of high pressures on destemmed grapes was effective as pasteurization treatment and also as enhancer of polyphenol extraction, achieving an increase of 12.4-18.5% in the average content of total anthocyanins. As expected, addition of flavonoids to the must, stimulated the formation of stable pigments, mainly as a result of condensation reactions between anthocyanins and flavanols mediated by acetaldehyde. With the use of Torulaspora delbrueckii strains in sequential fermentation with Saccharomyces cerevisiae, it was possible to increase the production of diacetyl and 2-phenylethyl acetate, besides the synthesis of a new compound: 3-ethoxy-1-propanol. The use of Schizosaccharomyces pombe (938, V1) and Torulaspora delbrueckii (1880) strains in sequential and mixed fermentations with Saccharomyces cerevisiae improved the sensory profile of red wine by increasing polyols synthesis and enhancing fruity, floral and herbaceous aromas, and it also increased the stability of the coloring matter by favouring vitisins and vinylphenolic pyranoanthocyanins formation. Ageing on lees in barrels from selected yeasts can improve the complexity and aromatic persistence of red wine, without major changes in the color.

A simple mathematical model that describes the growth of the area and the number of total and viable cells in yeast colonies

We propose a model, based on the Gompertz equation, to describe the growth of yeasts colonies on agar medium. This model presents several advantages: (i) one equation describes the colony growth, which previously needed two separate ones (linear increase of radius and of the squared radius); (ii) a similar equation can be applied to total and viable cells, colony area or colony radius, because the number of total cells in mature colonies is proportional to their area; and (iii) its parameters estimate the cell yield, the cell concentration that triggers growth limitation and the effect of this limitation on the specific growth rate. To elaborate the model, area, total and viable cells of 600 colonies of Saccharomyces cerevisiae, Debaryomyces fabryi, Zygosaccharomyces rouxii and Rhodotorula glutinis have been measured. With low inocula, viable cells showed an initial short exponential phase when colonies were not visible. This phase was shortened with higher inocula. In visible or mature colonies, cell growth displayed Gompertz-type kinetics. It was concluded that the cells growth in colonies is similar to liquid cultures only during the first hours, the rest of the time they grow, with near-zero specific growth rates, at least for 3 weeks.