The effect of nitrogen addition on the fermentative performance during sparkling wine production

Influence of different stress factors during the elaboration of grape must's pieddecuve on the dynamics of yeast populations during alcoholic fermentation

The pieddecuve (PdC) technique involves using a portion of grape must to undergo spontaneous fermentation, which is then used to inoculate a larger volume of must. This allows for promoting autochthonous yeasts present in the must, which can respect the typicality of the resulting wine. However, the real impact of this practice on the yeast population has not been properly evaluated. In this study, we examined the effects of sulphur dioxide (SO2), temperature, ethanol supplementation, and time on the dynamics and selection of yeasts during spontaneous fermentation to be used as PdC. The experimentation was conducted in a synthetic medium and sterile must using a multi-species yeast consortium and in un-inoculated natural grape must. Saccharomyces cerevisiae dominated both the PdC and fermentations inoculated with commercial wine yeast, displaying similar population growth regardless of the tested conditions. However, using 40 mg/L of SO2 and 1% (v/v) ethanol during spontaneous fermentation of Muscat of Alexandria must allowed the non-Saccharomyces to be dominant during the first stages, regardless of the temperature tested. These findings suggest that it is possible to apply the studied parameters to modulate the yeast population during spontaneous fermentation while confirming the effectiveness of the PdC methodology in controlling alcoholic fermentation.

Influence of the Dry Yeast Preparation Method on Final Sparkling Wine Characteristics

The effect of preparing the commercial yeast prise de mousse S. cerevisiae IOC 18-2007 on the second fermentation kinetics of a Macabeo white base wine was evaluated. The influence of yeast preparation on the final “Cava” sparkling wines was determined. The medium glucose, peptone, yeast extract (GPY medium), and the characteristic classic pied de cuve procedure were used to prepare the inoculum, which was placed besides a tirage liqueur inside bottles in which a second fermentation took place by the “traditional method”. The fermentation kinetics were similar for the first 60 days regardless of the employed yeast inoculum preparation. In both cases, glucose was exhausted and a few grams of fructose remained on day 30. The ethanol concentration after 60 days was the same in all of the wines. The sparkling wines inoculated with the GPY-grown yeasts showed higher titratable acidity, lower total polysaccharide and protein contents, and greater foamability (HM) and foam stability (HS). Regarding volatile compounds, these wines contained higher esters, fatty acids, higher alcohols, and γ-butyrolactone. Differences in the wine’s visual and flavor attributes were not significant no matter what inoculum was used. However, the aroma score was significantly higher in the wines inoculated with the pied de cuve-prepared yeasts.

Impact of Nitrogen Addition on Wine Fermentation by S. cerevisiae Strains with Different Nitrogen Requirements

In modern oenology, supplementation of nitrogen sources is an important strategy to prevent sluggish or stuck fermentation. The present study thoroughly determined the effect of nitrogen addition timing and nitrogen source type on fermentation kinetics and aroma production, carried out by yeast strains with low and high nitrogen requirements. The results revealed that yeast strains with different nitrogen requirements have divergent reactions to nitrogen addition. Nitrogen addition clearly shortened the fermentation duration, especially for the high-nitrogen-demanding yeast strain. Nitrogen addition at 1/3 fermentation was the most effective in terms of fermentation activity, nitrogen assimilation, and production of acetate esters. Interestingly enough, yeast cells preferentially took up amino acids related to fermentative aroma synthesis with the addition at 2/3 fermentation. The addition of nitrogen sources also largely affected the production of important metabolites. Generally speaking, acetic acid, glycerol, and succinic acid reduced with the supplementation of nitrogen sources. The results revealed significant application importance for the winemaking industry.

Impact of CO2 overpressure on yeast mitochondrial associated proteome during the "prise de mousse" of sparkling wine production

The "prise de mousse" stage during sparkling wine elaboration by the traditional method (Champenoise) involves a second fermentation in a sealed bottle followed by a prolonged aging period, known to contribute significantly to the unique organoleptic properties of these wines. During this stage, CO₂ overpressure, nutrient starvation and high ethanol concentrations are stress factors that affect yeast cells viability and metabolism. Since mitochondria are responsible for energy generation and are required for cell aging and response to numerous stresses, we hypothesized that these organelles may play an essential role during the prise de mousse. The objective of this study is to characterize the mitochondrial response of a Saccharomyces cerevisiae strain traditionally used in sparkling wine production along the "prise de mousse" and study the effect of CO₂ overpressure through a proteomic analysis. We observed that pressure negatively affects the content of mitochondrion-related proteome, especially to those proteins involved in tricarboxylic acid cycle. However, proteins required for the branched-amino acid synthesis, implied in wine aromas, and respiratory chain, also previously reported by transcriptomic analyses, were found over-represented in the sealed bottles. Multivariate analysis of proteins required for tricarboxylic cycle, respiratory chain and amino acid metabolism revealed differences in concentrations, allowing the wine samples to group depending on the time and CO₂ overpressure parameters. Ethanol content along the second fermentation could be the main reason for this changing behavior observed at proteomic level. Further research including genetic studies, determination of ROS, characterization of mitochondrial activity and targeted metabolomics analyses is required. The list of mitochondrial proteins provided in this work will lead to a better understanding of the yeast behavior under these conditions of special interest in the wine industry.

Influence of fermentation conditions on the secretion of seripauperin 5 (PAU5) by industrial sparkling wine strains of Saccharomyces cerevisiae

The yeast mannoprotein seripauperin 5 (PAU5) from Saccharomyces cerevisiae is a negative gushing biomarker in sparkling wine with a direct gushing-reducing effect. The knowledge about the influence of the yeast strain and the fermentation conditions on the PAU5 content in the final product could reduce the gushing potential of sparkling wines and avoid economic losses for sparkling wine producers. The potential of 30 different commercially used (sparkling) wine S. cerevisiae strains to produce PAU5 was analyzed by RP-HPLC. The experiments revealed great differences between strains and identified three high-PAU5-producing yeast strains. The influence of different fermentation conditions was analyzed in two selected strains. Cultivation conditions of elevated temperature and lower inoculation density, as well as cultivation under diffuse daylight significantly enhanced PAU5 production by the tested S. cerevisiae strains as compared to standard conditions. However, cultivation as agitated cultures and co-cultivation with Metchnikowia pulcherrima or Torulaspora delbrueckii led to a reduction of PAU5 production as compared to standard conditions.

Using an electronic nose and volatilome analysis to differentiate sparkling wines obtained under different conditions of temperature, ageing time and yeast formats

Effect of yeast inoculation format (F), temperature (T), and "on lees" ageing time (t) factors were evaluated on the composition of sparkling wines by a quantitative fingerprint obtained from volatile metabolites and the response of an electronic nose (E-nose). Wines elaborated according the traditional method at 10 and 14 °C, free cells and yeast biocapsules formats were monitored at 15 and 24 months of ageing time. Sixty-six volatiles identified and quantified in the eight sampling lots were subjected to a pattern recognition technique. A dual criterion based on univariate (ANOVA) and multivariate analysis (PLS-DA) through the variable importance projection (VIP) values, allowed to identify ten volatiles as potential markers for T factor, eleven for t and twelve for F factors. The discriminant models based on E-nose dataset enable a 100% correct classification of samples, in relation with t and F factors and the 83% for T factor.

Nutrient Addition to Low pH Base Wines (L. cv. Riesling) during Yeast Acclimatization for Sparkling Wine: Its Influence on Yeast Cell Growth, Sugar Consumption and Nitrogen Usage

In traditional method sparkling wine production, to carry out a successful second alcoholic fermentation, yeast are acclimatized to stressful base wine conditions. Base wines typically have low pH, low nutrient concentrations, high acid concentrations, contain sulfur dioxide (SO2), and high ethanol concentrations. Supplementing yeast during the acclimatization stages prior to second alcoholic fermentation with different nutrient sources was assessed to determine the impact on yeast growth, sugar consumption and nitrogen usage. Four treatments were tested with Saccharomyces cerevisiae strain EC1118: the control (T1) with no additives; addition of diammonium phosphate (DAP) during acclimatization, (T2); Go-Ferm® inclusion during yeast rehydration (GF), (T3); and DAP + GF (T4). Results (n = 4) indicated that supplementing with DAP, GF or DAP + GF increased both the rate of sugar consumption and the concentration of viable cells during the yeast acclimatization phase in comparison to the control. Treatments supplemented with DAP + GF or DAP alone resulted in yeast consuming 228 and 220 mg N/L during the acclimatization phase, respectively. Yeast treated only with GF consumed 94 mg N/L in comparison to the control, which consumed 23 mg N/L. The time required to reach the target specific gravity (1.010) during acclimatization was significantly reduced to 57 h for yeast treated with DAP and GF, 69 h for yeast treated with DAP only and 81 h for yeast rehydrated with GF in comparison to 105 h for the control. Our results suggest that nutrients used during yeast acclimatization could have an important impact on the kinetics of second alcoholic fermentation.

Effect of sulfite addition and pied de cuve inoculation on the microbial communities and sensory profiles of Chardonnay wines: dominance of indigenous Saccharomyces uvarum at a commercial winery

The microbial consortium of wine fermentations is highly dependent upon winemaking decisions made at crush, including the decision to inoculate and the decision to add sulfur dioxide (SO2) to the must. To investigate this, Chardonnay grape juice was subjected to two inoculation treatments (uninoculated and pied de cuve inoculation) as well as two SO2 addition concentrations (0 and 40 mg/L). The bacterial communities, fungal communities and Saccharomyces populations were monitored throughout fermentation using culture-dependent and culture-independent techniques. After fermentation, the wines were evaluated by a panel of experts. When no SO2 was added, the wines underwent alcoholic fermentation and malolactic fermentation simultaneously. Tatumella bacteria were present in significant numbers, but only in the fermentations to which no SO2 was added, and were likely responsible for the malolactic fermentation observed in these treatments. All fermentations were dominated by a genetically diverse indigenous population of Saccharomyces uvarum, the highest diversity of S. uvarum strains to be identified to date; 150 unique strains were identified, with differences in strain composition as a result of SO2 addition. This is the first report of indigenous S. uvarum strains dominating and completing fermentations at a commercial winery in North America.

Quantitative Trait Nucleotides Impacting the Technological Performances of Industrial Saccharomyces cerevisiae Strains

The budding yeast Saccharomyces cerevisiae is certainly the prime industrial microorganism and is related to many biotechnological applications including food fermentations, biofuel production, green chemistry, and drug production. A noteworthy characteristic of this species is the existence of subgroups well adapted to specific processes with some individuals showing optimal technological traits. In the last 20 years, many studies have established a link between quantitative traits and single-nucleotide polymorphisms found in hundreds of genes. These natural variations constitute a pool of QTNs (quantitative trait nucleotides) that modulate yeast traits of economic interest for industry. By selecting a subset of genes functionally validated, a total of 284 QTNs were inventoried. Their distribution across pan and core genome and their frequency within the 1,011 Saccharomyces cerevisiae genomes were analyzed. We found that 150 of the 284 QTNs have a frequency lower than 5%, meaning that these variants would be undetectable by genome-wide association studies (GWAS). This analysis also suggests that most of the functional variants are private to a subpopulation, possibly due to their adaptive role to specific industrial environment. In this review, we provide a literature survey of their phenotypic impact and discuss the opportunities and the limits of their use for industrial strain selection.

The Impact of Non-Saccharomyces Yeast on Traditional Method Sparkling Wine

The interest in non-Saccharomyces yeast for use in sparkling wine production has increased in recent years. Studies have reported differences in amino acids and ammonia, volatile aroma compounds (VOCs), glycerol, organic acids, proteins and polysaccharides. The aim of this review is to report on our current knowledge concerning the influence of non-Saccharomyces yeast on sparkling wine chemical composition and sensory profiles. Further information regarding the nutritional requirements of each of these yeasts and nutrient supplementation products specifically for non-Saccharomyces yeasts are likely to be produced in the future. Further studies that focus on the long-term aging ability of sparkling wines made from non-Saccharomyces yeast and mixed inoculations including their foam ability and persistence, organic acid levels and mouthfeel properties are recommended as future research topics.

Balsamic type varietal vinegar from cv. Xinomavro (Northen Greece). Optimization and scale-up of the alcoholic fermentation step using indigenous multistarters

Taguchi design was used to examine the effect of parameters that should be optimized in order to control the alcoholic fermentation of the concentrated grape must (CGM) from cv. Xinomavro using the best-performing indigenous Hanseniaspora uvarum and Saccharomyces cerevisiae strains as multistarters. The "optimum" combination of conditions (cell ratio of H. uvarum/S. cerevisiae; inoculum size and inoculation time of S. cerevisiae; fermentation time and temperature) resulted in an alcoholic product that meets ethanol (79 g/kg) and residual sugar (164 g/kg) content requirements for further use in the production of balsamic type vinegar. Multistarter fermentation affected positively the varietal organoleptic traits of the fermented CGM. 5-(Hydroxymethyl)-furfural content emerged as a critical factor for the standardization of this process. Scaling up experiments in 12 L barrels verified findings from small scale in 100 mL flasks. The results of this work can be used as a prototype in further similar efforts.

Genetic Causes of Phenotypic Adaptation to the Second Fermentation of Sparkling Wines in Saccharomyces cerevisiae

Hybridization is known to improve complex traits due to heterosis and phenotypic robustness. However, these phenomena have been rarely explained at the molecular level. Here, the genetic determinism of Saccharomyces cerevisiae fermentation performance was investigated using a QTL mapping approach on an F1-progeny population. Three main QTL were detected, with positive alleles coming from both parental strains. The heterosis effect found in the hybrid was partially explained by three loci showing pseudooverdominance and dominance effects. The molecular dissection of those QTL revealed that the adaptation to second fermentation is related to pH, lipid, or osmotic regulation. Our results suggest that the stressful conditions of second fermentation have driven the selection of rare genetic variants adapted to maintain yeast cell homeostasis and, in particular, to low pH conditions.

Contribution of yeast and base wine supplementation to sparkling wine composition

BACKGROUND

The differential characteristic of sparkling wine is the formation of foam, which is dependent, among other factors, on yeast autolysis, aging and oenological practices. In this study, we analyzed the effects of yeast strain, nutrient supplementation to the base wine and aging process on the sparkling wine composition and its foamability.

RESULTS

We determined that the addition of inorganic nitrogen promoted nitrogen liberation to the extracellular medium, while the addition of inactive dry yeast to the base wine caused an increase in the polysaccharide concentration and foaming properties of the sparkling wine. The use of synthetic and natural base wines allowed us to discriminate that the differences in high-molecular-weight polysaccharides and oligosaccharides could be attributed to the yeast cells and that the higher nitrogen content in the natural wine could be due to external proteolysis.

CONCLUSION

The practices of nitrogen addition and supplementation of inactive dry yeast could modulate the main characteristics of the sparkling wine and be a critical element for the design of this kind of wine. © 2016 Society of Chemical Industry.

Characterization of Active Dry Wine Yeast During Starter Culture (Pied de Cuve) Preparation for Sparkling Wine Production

The preparation of yeast starter culture (Pied de Cuve) for producing sparkling wine with the traditional method is a key factor for manufacturing a good Prise de mousse. In this paper, the evolution of total yeast population, its viability during Pied de Cuve preparation, and the pressure profile during the 2nd fermentation in 2 different base wines made from Bombino bianco and Chardonnay grapes were investigated using 4 different commercial active dried yeasts. The study proves that despite the initial differences observed throughout the acclimatization phase, all the tested strains showed similar results on either the total population (from 8.2 × 10(7) cells/mL to 1.3 × 10(8) cells/mL) or cellular viability (from 70% to 84%). Independently from the base wine tested, the kinetic of sugar consumption was faster during the gradual acclimatization to the alcoholic medium (phase II) and slower during the preparation of starter culture in active growth phase (phase III). During both of these phases Saccharomyces cerevisiae bayanus Vitilevure DV10(®) (Station œnotechnique de Champagne) proved to have a higher sugar consumption rate than the other strains. During the Prise de mousse, S. cerevisiae bayanus Lalvin EC-1118(®) (Lallemand) reached the maximum pressure increase within time in both base wines.