Improving an Industrial Sherry Base Wine by Yeast Enhancement Strategies.

There is growing interest in yeast selection for industrial fermentation applications since it is a factor that protects a wine's identity. Although it is strenuous evaluating the oenological characteristics of yeasts in selection processes, in many cases the most riveting yeasts produce some undesirable organoleptic characteristics in wine. The aim of the present work is to improve an industrial yeast strain by reducing its hydrogen sulfide (H2S) production. To accomplish this, two different improvement approaches were used on said yeast: hybridization by mass mating and adaptive laboratory evolution, both performed through spore generation and conjugation, thus increasing genetic variability. Three evolved variants with lower H2S production were obtained and used as starters to carry out fermentation at an industrial level. Wine quality was analyzed by its principal oenological parameters and volatile aroma compounds, which were both corroborated by sensory evaluations. Significant differences between the produced wines have been obtained and a substantial improvement in aromatic quality has been achieved. Both hybrids were the most different to the control due to terpenes and esters production, while the evolved strain was very similar to the parental strain. Not only have organoleptic defects been reduced at an industrial level, more floral and fruitier wines have been produced.

Comprehensive Chemical and Sensory Assessment of Wines Made from White Grapes of Vitis vinifera Cultivars Albillo Dorado and Montonera del Casar: A Comparative Study with Airén.

The ability to obtain different wines with a singular organoleptic profile is one of the main factors for the wine industry's growth, in order to appeal to a broad cross section of consumers. Due to this, white wines made from the novel grape genotypes Albillo Dorado and Montonera del Casar (Vitis vinifera L.) were studied and compared to the well-known Airén at two consecutive years. Wines were evaluated by physicochemical, spectrophotometric, high-performance liquid chromatography-diode array detection-mass spectrometry, gas chromatography-mass spectrometry and sensory analyses. The chromatic characteristics of the new wines were defined by more color purity than Airén, with greenish highlights. In general, the phenolic profile of the Albillo Dorado wines showed a higher flavonol and hydroxycinnamic acid derivative content. Several volatile compounds were determined, and their odor activity values were calculated to determine their impact on wine aroma. A fruity series dominated the wine aromatic composition, but spicier and greener notes characterized the aroma profile of Airén wines. Albillo Dorado and Montonera del Casar were sensory evaluated as wines with a less fresh taste compared to Airén. Unique chemical and sensory profiles were determined for wines made from these novel grape genotypes, providing alternative monovarietal wines to encourage the wine market growth and extend the offer to consumers.

Potential of Different Natural Antioxidant Substances to Inhibit the 1-Hydroxyethyl Radical in SO2-Free Wines.

The potential of different natural antioxidants to inhibit the 1-hydroxyethyl radical formation in SO2-free wines was analyzed by electron paramagnetic resonance (EPR). Chitosan, glutathione, inactive dry yeast, oak and grape seed extracts, and ascorbic acid were tested in white and red wines. The ability of these substances to prevent the formation of acetaldehyde after the Fenton reaction and the oxygen consumption capacity were measured. Ascorbic acid was the antioxidant substance that offered higher percentages of 1-hydroxyethyl radical inhibition at 30 min of reaction. However, wines with ascorbic acid showed higher concentrations of acetaldehyde after the Fenton reaction. Grape seed extract and chitosan provided higher percentages of radical inhibition in red wine than those in white wine, in contrast to the inactive dry yeast that only produced radical inhibition in white wine. Although oak extract did not produce changes in the 1-hydroxyethyl radical, wines with that extract had lower concentrations of acetaldehyde.

Flavanol Glycoside Content of Grape Seeds and Skins of Vitis vinifera Varieties Grown in Castilla-La Mancha, Spain.

Glycosylated flavanols (monoglycosides and diglycosides) in skin and seed extracts of Vitis vinifera grapes grown in Castilla-La Mancha (Spain) were investigated using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-ESI-QQQ-MS/MS). Six grape varieties (Airén, Tempranillo, the recently identified Albillo Dorado, Montonera del Casar, Moribel, and Tinto Fragoso) were studied over two consecutive years (2016 and 2017). A total of twenty monomeric flavanol monoglycosides, four diglycosylated monomers, and three dimeric flavanol monoglycosides were detected in all grape samples. The diversity observed in the composition of glycosylated flavanol in the grape berries suggests a strong influence of variety and grape tissue (skin or seed). Monomeric flavanol glycosides were more abundant in grape seed extracts, in contrast with monoglycosylated dimeric forms. In addition, the glycosylated flavanol content was related to berry color in grape skins, with higher concentrations measured in black grape varieties.

LC-MS/MS analysis of free fatty acid composition and other lipids in skins and seeds of Vitis vinifera grape cultivars.

Lipids are important constituents of plant and animal cells, being essential due to their biological functions. Despite the significant role of these compounds in grape berries, knowledge of grape lipid composition is still limited. This study addresses the free fatty acid composition and other lipids in skins and seeds of several Vitis vinifera grape cultivars using LC-MS/MS. A different profile of free fatty acids was determined in the grape tissues, showing a higher proportion of unsaturated fatty acids in seeds (ca. 60%). Lignoceric acid was one of the main free saturated fatty acids found in grape skins, together with palmitic and stearic acids. Berry skins showed similar ranges of C18-unsaturated fatty acids, whereas linoleic acid was predominant in the seed fatty acid composition. Higher content of glycerophospholipids was determined in grape seeds. Uvaol and oleanolic acid were only quantified in skins (1.5-3.9 and 38.6-57.6 mg/kg fresh weight, respectively). These preliminary results suggest a certain diversity in grape lipids according to their location in the berry tissues and cultivar, providing useful information for the fermentation process due to their role in wine sensory profile and yeast growth.

Phenolic compounds profile of different berry parts from novel Vitis vinifera L. red grape genotypes and Tempranillo using HPLC-DAD-ESI-MS/MS: A varietal differentiation tool.

The detailed phenolic composition of different berry parts from two novel V. vinifera L. red grape genotypes (Moribel and Tinto Fragoso), together the well-known Tempranillo, was established using high performance liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) over two consecutive vintages (2016 and 2017). More than 50 phenolic compounds were identified and quantified: 25 anthocyanins, 17 flavonols, 7 hydroxycinnamic acid derivatives, 2 stilbenes, and several flavan-3-ols. As far as we know, some anthocyanin and flavonol dihexosides were reported for the first time in V. vinifera L. grapes. Application of Principal Component Analysis (PCA) to experimental data showed a good separation of the novel grape genotypes and Tempranillo according to the phenolic profile of skins and seeds, mainly based on the proportion of trisubstituted anthocyanin derivatives, flavonols and flavan-3-ols, being a useful tool to differentiate these grape varieties.

Influence of inoculation time of an autochthonous selected malolactic bacterium on volatile and sensory profile of Tempranillo and Merlot wines.

A study was carried out to determine the effect of the inoculation time of the lactic acid bacteria (LAB) on the kinetic of vinification and on chemical and sensory characteristics of Tempranillo and Merlot wines. Traditional vinifications, with LAB inoculated after completion of AF, were compared with vinifications where yeast and bacteria were co-inoculated. Two commercial yeast strains and an autochthonous Oenococcus oeni strain (C22L9) previously identified and selected at our laboratory were used. Monitoring of alcoholic and malolactic fermentations was carried out by yeast and lactic acid bacteria counts and by measuring contents of glucose+fructose, malic acid and lactic acid. The implantation rate of O. oeni C22L9 was calculated by typing isolates obtained from count plates using the RAPD-PCR (Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction) technique. Wines were chemically characterised and analysed for biogenic amine and volatile compound contents. A sensory analysis, consisting in a descriptive and a triangular test was also carried out. Results from this study showed that for both grape varieties, the concurrent yeast/bacteria inoculation of musts produced a significant reduction in duration of the process, without a pronounced degradation of malic acid during AF, nor an excessive increase in volatile acidity. Biogenic amine content was also lower in wines produced by co-inoculation. Important differences in volatile compound contents were observed, although there was little impact on the sensorial profile of wines. These results suggest that co-inoculation using O. oeni C22L9 is a worthwhile alternative compared to traditional post AF inoculation for Tempranillo and Merlot winemaking.