The Role of Yeasts and Lactic Acid Bacteria on the Metabolism of Organic Acids during Winemaking.

The main role of acidity and pH is to confer microbial stability to wines. No less relevant, they also preserve the color and sensory properties of wines. Tartaric and malic acids are generally the most prominent acids in wines, while others such as succinic, citric, lactic, and pyruvic can exist in minor concentrations.

Effect of Controlled Microbial Fermentation on Nutritional and Functional Characteristics of Cowpea Bean Flours.

This study aimed to optimize bean flours fermentation through the use of appropriate technological procedure and, thereby, to obtain a high quality and safe product. In this line, cowpea bean flours with different moisture conditions (10, 20 and 30%) were incubated with (1) a single culture of , or (2) a consortium of lactic acid and acetic acid bacteria, together with one strain of . Effects of inoculation of cowpea beans flours on stability (i.

Characterizing the Potential of the Non-Conventional Yeast UTAD17 in Winemaking.

Non- yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, is one of the less studied species. In the present study, a native strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits.

Volatile Composition and Sensory Properties of Mead.

Mead is a traditional beverage that results from the alcoholic fermentation of diluted honey performed by yeasts. Although the process of mead production has been optimized in recent years, studies focused on its sensory properties are still scarce. Therefore, the aim of this work was to analyse the sensory attributes of mead produced with free or immobilized cells of the strains QA23 and ICV D47, and to establish potential correlations with its volatile composition.

Production of blueberry wine and volatile characterization of young and bottle-aging beverages.

The aim of this study was the production of blueberry wine and the characterization of the volatile compounds of fermented and aging in bottle products. Multivariate data analysis indicated similarity of volatile compounds released when fermentations were conducted at laboratory-scale and midscale, with the exception of one replicate creating a distinctive group characterized by low concentrations of acetaldehyde, methanol, 1-hexanol, and ethyl hexanoate, and the production of polyalcohols such as 2,3-butanediols. This experiment was the only one where no adjustments of were performed.

Genome Sequence of the Wine Yeast UTAD17.

This work describes, for the first time, the genome sequence of a Saccharomycodes ludwigii strain. Although usually seen as a wine spoilage yeast, S. ludwigii has been of interest for the production of fermented beverages because it harbors several interesting properties, including the production of beneficial aroma compounds.

Genome sequence of the non-conventional wine yeast Hanseniaspora guilliermondii UTAD222 unveils relevant traits of this species and of the Hanseniaspora genus in the context of wine fermentation.

Hanseanispora species, including H. guilliermondii, are long known to be abundant in wine grape-musts and to play a critical role in vinification by modulating, among other aspects, the wine sensory profile. Despite this, the genetics and physiology of Hanseniaspora species remains poorly understood.

Genome Sequence of the Nonconventional Wine Yeast Hanseniaspora guilliermondii UTAD222.

In this work, we disclose the genome sequence and a corresponding manually curated annotation of the non-Saccharomyces yeast Hanseniaspora guilliermondii UTAD222, a strain shown to have interesting oenological traits for the production of wines with improved aromatic properties.

Characterization of neural network generalization in the determination of pH and anthocyanin content of wine grape in new vintages and varieties.

The generalization ability of hyperspectral imaging combined with neural networks (NN) in estimating pH and anthocyanin content during ripening was evaluated for vintages and varieties not employed in the NN creation. A NN, from a previously published work, trained with grape samples of Touriga Franca (TF) variety harvested in 2012 was tested with TF from 2013 and two new varieties, Touriga Nacional (TN) and Tinta Barroca (TB) from 2013. Each sample contained a small number of whole berries.

Genomic expression program of Saccharomyces cerevisiae along a mixed-culture wine fermentation with Hanseniaspora guilliermondii.

Background: The introduction of yeast starter cultures consisting in a blend of Saccharomyces cerevisiae and non-Saccharomyces yeast strains is emerging for production of wines with improved complexity of flavor. The rational use of this approach is, however, dependent on knowing the impact that co-inoculation has in the physiology of S. cerevisiae.

Biodegradation of ochratoxin A by Pediococcus parvulus isolated from Douro wines.

Lactic acid bacteria (LAB) are a promising solution to reduce exposure to dietary mycotoxins because of the unique mycotoxin decontaminating characteristic of some LAB. Ochratoxin A (OTA) is one of the most prominent mycotoxins found in agricultural commodities. The present work reports on the ability of Pediococcus parvulus strains that were isolated from Douro wines that spontaneously underwent malolactic fermentation to detoxify OTA.

Phenotypic and metabolic traits of commercial Saccharomyces cerevisiae yeasts.

Currently, pursuing yeast strains that display both a high potential fitness for alcoholic fermentation and a favorable impact on quality is a major goal in the alcoholic beverage industry. This considerable industrial interest has led to many studies characterizing the phenotypic and metabolic traits of commercial yeast populations. In this study, 20 Saccharomyces cerevisiae strains from different geographical origins exhibited high phenotypic diversity when their response to nine biotechnologically relevant conditions was examined.

H. guilliermondii impacts growth kinetics and metabolic activity of S. cerevisiae: the role of initial nitrogen concentration.

Non-Saccharomyces yeasts include different species which comprise an ecologically and biochemically diverse group capable of altering fermentation dynamics and wine composition and flavour. In this study, single- and mixed-culture of Hanseniaspora guilliermondii and Saccharomyces cerevisiae were used to ferment natural grape-juice, under two nitrogen regimes. In single-culture the strain H.

Reduction of volatile acidity of acidic wines by immobilized Saccharomyces cerevisiae cells.

Excessive volatile acidity in wines is a major problem and is still prevalent because available solutions are nevertheless unsatisfactory, namely, blending the filter-sterilized acidic wine with other wines of lower volatile acidity or using reverse osmosis. We have previously explored the use of an empirical biological deacidification procedure to lower the acetic acid content of wines. This winemaker's enological practice, which consists in refermentation associated with acetic acid consumption by yeasts, is performed by mixing the acidic wine with freshly crushed grapes, musts, or marc from a finished wine fermentation.

The nitrogen source impacts major volatile compounds released by Saccharomyces cerevisiae during alcoholic fermentation.

Sulphur-containing amino acids, cysteine and methionine, are generally found in very low concentrations in grape-juice. The objective of this study was to identify the effects of methionine on aroma compounds formation. Nitrogen source effects on growth, fermentative behaviour and aroma compounds formation were evaluated in three strains of Saccharomyces cerevisiae cultivated in batch under moderate nitrogen concentration, 267mg YAN/L, supplied as di-ammonium phosphate (DAP), a mixture of amino acids with (AA) or without methionine (AA(wMet)), and a mixture of AA plus DAP.

High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production.

Mead is a traditional drink that contains 8%-18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles.

Accumulation of non-superoxide anion reactive oxygen species mediates nitrogen-limited alcoholic fermentation by Saccharomyces cerevisiae.

Throughout alcoholic fermentation, nitrogen depletion is one of the most important environmental stresses that can negatively affect the yeast metabolic activity and ultimately leads to fermentation arrest. Thus, the identification of the underlying effects and biomarkers of nitrogen limitation is valuable for controlling, and therefore optimizing, alcoholic fermentation. In this study, reactive oxygen species (ROS), plasma membrane integrity, and cell cycle were evaluated in a wine strain of Saccharomyces cerevisiae during alcoholic fermentation in nitrogen-limiting medium under anaerobic conditions.

Optimization of honey-must preparation and alcoholic fermentation by Saccharomyces cerevisiae for mead production.

Mead fermentation is a time-consuming process, often taking several months to complete. Despite of the use of starter cultures several problems still persist such as lack of uniformity of the final products, slow or premature fermentation arrest and the production of off-flavors by yeast. Thus the aim of this study was to optimize mead production through the use of an appropriate honey-must formulation to improve yeast performance alcoholic fermentation and thereby obtain a high quality product.

The impact of acetate metabolism on yeast fermentative performance and wine quality: reduction of volatile acidity of grape musts and wines.

Acetic acid is the main component of the volatile acidity of grape musts and wines. It can be formed as a by-product of alcoholic fermentation or as a product of the metabolism of acetic and lactic acid bacteria, which can metabolize residual sugars to increase volatile acidity. Acetic acid has a negative impact on yeast fermentative performance and affects the quality of certain types of wine when present above a given concentration.

The wine yeast strain-dependent expression of genes implicated in sulfide production in response to nitrogen availability.

Sulfur metabolism in S. cerevisiae is well established, but the mechanisms underlying the formation of sulfide remain obscure. Here we investigated by real time RT-PCR the dependence of expression levels of MET3, MET5/ECM17, MET10, MET16 and MET17 along with SSU1 on nitrogen availability in two wine yeast strains that produce divergent sulfide profiles.

Effect of refermentation conditions and micro-oxygenation on the reduction of volatile acidity by commercial S. cerevisiae strains and their impact on the aromatic profile of wines.

Herein, we evaluate the applicability of previously characterized commercial and indigenous Saccharomyces cerevisiae strains and non-S. cerevisiae species for the deacidification of white and red wines at a pilot scale. The effect of the refermentation process (mixture of acidic wine with musts from freshly crushed grapes or with residual marc) as well as micro-oxygenation (MO) on acetic acid removal efficiency and wine aromatic composition was also assessed in a red wine.

Effects of acetic acid, ethanol, and SO(2) on the removal of volatile acidity from acidic wines by two Saccharomyces cerevisiae commercial strains.

Herein, we report the influence of different combinations of initial concentration of acetic acid and ethanol on the removal of acetic acid from acidic wines by two commercial Saccharomyces cerevisiae strains S26 and S29. Both strains reduced the volatile acidity of an acidic wine (1.0 gl(-1) acetic acid and 11% (v/v) ethanol) by 78% and 48%, respectively.

Characterisation of free and glycosidically bound odourant compounds of Aragonez clonal musts by GC-O.

To evaluate the potential aroma of Aragonez clonal red musts, several free and glycosidically bound odourant compounds were extracted. Then, the gas chromatography-olfactometry (GC-O) posterior intensity method was used to evaluate their odour intensity and the compounds were identified by gas chromatography-mass spectrometry (GC-MS). A group of eight sniffers evaluated free and bound fractions of Aragonez musts and perceived forty-three and twenty-two odourant peaks respectively.

The timing of diammonium phosphate supplementation of wine must affects subsequent H2S release during fermentation.

Aims: The aim of this study was to evaluate the impact of supplementation by diammonium phosphate (DAP) on hydrogen sulfide (H(2)S) production, when DAP given either prior to fermentation or during the early stationary growth phase of yeast.

Methods And Results: Three contrasting Saccharomyces cerevisiae wine strains were used to ferment synthetic grape juice (GJ) containing 67 mg l(-1) of initial yeast assimilable nitrogen (YAN), supplied either as DAP or as mixture of amino acids. Sufficient DAP was added either prior to or 72 h after the initiation of fermentation to achieve a final YAN concentration of 267 mg l(-1).