A comparative study of Lachancea thermotolerans fermentative performance under standardized wine production conditions

The study explores diverse strains of Lachancea thermotolerans in single-inoculum wine fermentation conditions using synthetic grape must. It aims to analyze the role of the species without external influences like other microorganisms or natural grape must variability. Commercial strains and selected vineyard isolates, untested together previously, are assessed. The research evaluates volatile and non-volatile chemical compounds in final wine, revealing significant strain-based variations. L. thermotolerans notably produces lactic acid and consumes malic acid, exhibiting moderate ethanol levels. The volatile profile displays strain-specific impacts, affecting higher alcohol and ester concentrations compared to S. cerevisiae. These effects vary based on the specific compounds. Using a uniform synthetic must enables direct strain comparisons, eliminating grape-related, environmental, or timing variables in the experiment, facilitating clearer insights into the behavior of L. thermotolerans in wine fermentation. The study compares for the first time all available commercial strains of L. thermotolerans.

Improvement of Must Fermentation from Late Harvest cv. Tempranillo Grapes Treated with Pulsed Light

Pulsed light irradiation is a nonthermal technology currently used for the elimination of pathogens from a diverse range of food products. In the last two decades, the results obtained using PL at laboratory scale are encouraging wine experts to use it in the winemaking industry. PL can reduce native yeast counts significantly, which facilitates the use of starter cultures, reducing SO2 requirements at the same time. In this experimental set up, Tempranillo grapes were subjected to pulsed light treatment, and the fermentative performance of non-Saccharomyces yeasts belonging to the species Schizosaccharomyces pombe, Lachancea thermotolerans, Torulaspora delbrueckii, Metschnikowia pulcherrima and Hanseniaspora vineae was monitored in sequential fermentations against spontaneous fermentation and pure culture fermentation with the species Saccharomyces cerevisiae. The experimental analyses comprised the determination of anthocyanin (High performance liquid chromatography with photodiode array detector-HPLC-DAD), polyphenol index and colour (Ultraviolet-visible spectroscopy-UV-Vis spectrophotometer), fermentation-derived volatiles (Gas chromatography with flame ionization detector-GC-FID), oenological parameters (Fourier transform Infrared spectroscopy-FT-IR) and structural damage of the skin (atomic force microscopy-AFM). The results showed a decrease of 1.2 log CFU/mL yeast counts after pulsed light treatment and more rapid and controlled fermentation kinetics in musts from treated grapes than in untreated samples. The fermentations done with treated grapes allowed starter cultures to better implant in the must, although a larger anthocyanin loss (up to 93%) and an increase in hue values (1 unit) towards more yellow hues were observed for treated grapes. The development of biomass was larger in musts from treated grapes. The profile of volatile compounds and oenological parameters reveals that fermentations carried out with untreated grapes are prone to deviations from native microbiota (e.g., production of lactic acid). Finally, no severe damage on the skin was observed with the AFM on treated grapes.

Formation of polymeric pigments in red wines through sequential fermentation of flavanol-enriched musts with non-Saccharomyces yeasts

Non-Saccharomyces yeasts may contribute to enrich wine aroma while promoting the formation of stable pigments. Yeast metabolites such as acetaldehyde and pyruvate participate in the formation of stable pigments during fermentation and wine aging. This work evaluated the formation of polymeric pigments in red musts added with (+)-Catechin, ProcyanidinB2 and ProcyanidinC1. The non-Saccharomyces yeasts used were Lachancea thermotolerans, Metschnikowia pulcherrima and Torulaspora delbrueckii in sequential fermentation with Saccharomyces cerevisiae and Schizosaccharomyces pombe. Use of Lachancea thermotolerans led to larger amounts of polymeric pigments in sequential fermentation. (+)-Catechin is the flavanol prone to forming such pigments. The species Metschnikowia pulcherrima produced higher concentration of esters and total volatile compounds. The sensory analysis pointed out differences in fruitiness and aroma quality. The results obtained strengthen the fact that metabolites from non-Saccharomyces yeasts may contribute to form stable polymeric pigments while also influencing wine complexity.

The Effects of Pre-Fermentative Addition of Oenological Tannins on Wine Components and Sensorial Qualities of Red Wine

Today in the wine industry, oenological tannins are widely used to improve wine quality and prevent oxidation in wine aging. With the development of tannin products, new oenological tannins are developed with many specific functions, such as modifying antioxidant effect, colour stabilization and aroma modifications. The aim of this work is to investigate effects of pre-fermentative addition of oenological tannins on wine colour, anthocyanins, volatile compounds and sensorial properties. In this case, Syrah juice was extracted with classic flash thermovinification from fresh must in order to release more colour and tannins. Three types of oenological tannins, which are, respectively, derived from grape skin, seed (Vitis vinifera) and French oak (Quercus robur and Querrus petraea), were selected to carry out the experiments with seven treatments. Results indicated that tannin treatments significantly improved wine aroma complexity and sensorial properties. However, the concentration of some stable pigments such as Vitisin A, Vitisin A-Ac and Vitisin B was negatively affected by tannin additions. Nevertheless, by means of cluster analysis and principal component analysis, it was observed that higher alcohols were significantly promoted by grape seed tannin while most anthocyanins can be improved by addition of grape tannins. In conclusion, low amount of oenological tannin derived from grape seed is a promising method to be applied especially for young red wine making.

Characterization of polymeric pigments and pyranoanthocyanins formed in microfermentations of non-Saccharomyces yeasts

AIMS

To assess the influence of non-Saccharomyces yeasts on the pyranoanthocyanins and polymeric pigments formation after the addition of (+)-catechin and procyanidin B2 to fresh red grape must.

METHODS AND RESULTS

The fermentation of red grape musts was done with non-Saccharomyces yeasts either alone or in sequential fermentations with the Saccharomyces cerevisiae species. The characterization of both pyranoanthocyanin and polymeric pigments has been carried out with liquid chromatography coupled to mass spectroscopy (HPLC-DAD-ESI/MS). Red wines were also characterized by infrared spectroscopy (FTIR), gas chromatography (GC-FID) and spectrophotometry (UV-Vis). It has been observed that fermentation with the species Schizosaccharomyces pombe led to higher concentrations of pigments of all types: anthocyanins, polymeric pigments and pyranoanthocyanins, particularly vitisin A.

CONCLUSIONS

The use of non-Saccharomyces yeasts improve the formation of stable pigments in red wines thanks to the differences in the microbial metabolism from among the yeasts studied.

SIGNIFICANCE AND IMPACT OF THE STUDY

Colour stability as one of the main organoleptic properties in red wines, may be improved by the controlled use of selected non-Saccharomyces yeasts during red must fermentation.

Yeast influence on the formation of stable pigments in red winemaking

The anthocyanin profile of a wine greatly varies over time depending on many factors. In addition to color modifications due to changes in the chemical composition of wine, there may be some influence of the yeast strain used in fermentation. The main aim of this study is to identify and quantify the different ways in which yeast may influence on wine color and its stability, during red winemaking. Hydroxycinnamate decarboxylase activity was measured by the ability to transform the p-coumaric acid (HPLC-DAD). Acetaldehyde (GC-FID) and pyruvic acid (Y15 enzymatic autoanalyser) contents were monitored along fermentation. Stable pigments formation, including vitisins, vinylphenolic pyranoanthocyanins and flavanols-anthocyanins adducts, were analyzed by HPLC-DAD/ESI-MS. Moreover, the ability of adsorbing color molecules by yeasts' cell walls was assessed. It could be concluded that the strain used has substantial influence on the formation of stable pigments, and therefore, proper yeast selection is important to ensure the stability of the wine coloring matter.

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

Hydroxycinnamate decarboxylase (HCDC) activity has been evaluated in several commercial yeast strains. The combined effect of using cinnamyl esterases (CE) and HCDC+ Saccharomyces cerevisiae strains has been studied in the formation of vinylphenolic pyranoanthocyanins (VPAs) during fermentation, analysing the kind and concentration of pigments formed according to the yeast strain used. Wines fermented with yeasts HCDC+ were contaminated with Dekkera bruxellensis and afterwards analysed to evaluate the formation of ethylphenols (EPs). The musts treated with CE and later fermented with HCDC+ yeast strains showed lower contents of 4-ethylphenol than those fermented with HCDC- strains. This reduction in the EP content is due to the transformation of hydroxycinnamic acids in stable VPAs pigments. The associated use of CEs and HCDC+ Saccharomyces strains is a natural strategy to reduce the formation of EPs in wines contaminated by Dekkera/Brettanomyces.

Evolution of phenolic compounds during an experimental aging in wood of Sherry vinegar

Changes in the physicochemical composition of wine vinegars produced by submerged culture system and aged in wood were followed. Five Sherry wine vinegars and a model vinegar solution were aged in six new American oak butts of 16.6 L capacity. A total of 24 phenolic compounds were monitored during the maturation study (24 months), along with other physicochemical parameters (total extract, acidity, residual alcohol and total phenolic index). Multivariate statistical analysis was applied to the data. From the sixth month on, significant changes were produced in most of the phenolic compounds, mainly aromatic aldehydes and 5-(hydroxymethyl)-2-furaldehyde. When all the phenolic compounds were considered as variables, cluster analysis grouped samples according to the wine substrate employed in the elaboration of vinegars under study. Within each subcluster, samples are arranged according to their aging status when phenolic compounds accounting significative changes at 180 days of aging are considered. Discriminant functions were constructed from the phenolic compounds data set. The validity of these functions was tested using 13 samples of aged commercial Sherry wine vinegars and 25 unaged vinegars. A total of 97.4% of the test samples was correctly classified within its respective group.

Evolution of the aroma profile of sherry wine vinegars during an experimental aging in wood

Changes in the aroma profile of five Sherry wine vinegars submitted to an experimental static aging in wood were followed along 24 months. Eighteen volatile compounds were determined by GC-FID. The results were subjected to multivariate analyses: principal component analysis and linear discriminant analysis. The aroma profile of vinegar can be useful to discriminate vinegars produced from different substrates or with different aging times. During the experimental aging, volatile compounds such as methyl acetate, methanol, diacetyl, and gamma-butyrolactone underwent significant concentration increases. Moreover, the initial ethanol content of vinegars is a factor in the final aromatic richness. The formation of ethyl acetate stood out in samples with an initial ethanol content of approximately 2 alcoholic degrees.