Influence of different Lachancea thermotolerans strains in the wine profile in the era of climate challenge.

The study performed sequential fermentations of red grape juice using several strains of Lachancea thermotolerans and one strain of Saccharomyces cerevisiae. Due to the new conditions imposed by climate change, wine acidity must be affected as well as the volatile profile. Non-Saccharomyces yeasts such as L. thermotolerans are real alternatives to soften the impact of climate change in winemaking. The L. thermotolerans strains included three commercially available strains and two wine-related natural isolates. L. thermotolerans showed significant statistical differences in basic chemical parameters such as lactic acid, malic acid, or ethanol concentrations as well as in the volatile profile. S. cerevisiae clearly produced some volatile compounds in higher amounts than the studied L. thermotolerans strains while others showed the opposite effect. Sequential fermentations involving any of the studied strains of L. thermotolerans with S. cerevisiae showed an increased volatile profile compared to the S. ceresisiae single fermentation, highlighting the synergic effect between the studied species.

High Potential of Pichia kluyveri and Other Pichia Species in Wine Technology.

The surfaces of grapes are covered by different yeast species that are important in the first stages of the fermentation process. In recent years, non-Saccharomyces yeasts such as Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, and Pichia kluyveri have become popular with regard to winemaking and improved wine quality. For that reason, several manufacturers started to offer commercially available strains of these non-Saccharomyces species. P. kluyveri stands out, mainly due to its contribution to wine aroma, glycerol, ethanol yield, and killer factor. The metabolism of the yeast allows it to increase volatile molecules such as esters and varietal thiols (aroma-active compounds), which increase the quality of specific varietal wines or neutral ones. It is considered a low- or non-fermentative yeast, so subsequent inoculation of a more fermentative yeast such as Saccharomyces cerevisiae is indispensable to achieve a proper fermented alcohol. The impact of P. kluyveri is not limited to the grape wine industry; it has also been successfully employed in beer, cider, durian, and tequila fermentation, among others, acting as a promising tool in those fermentation processes. Although no Pichia species other than P. kluyveri is available in the regular market, several recent scientific studies show interesting improvements in some wine quality parameters such as aroma, polysaccharides, acid management, and color stability. This could motivate yeast manufacturers to develop products based on those species in the near future.

Effect of alcoholic and acetous fermentations on the phenolic acids of Kei-apple (Dovyalis caffra L.) fruit.

BACKGROUND: The Kei apple is a tree found on the African continent. Limited information exists on the effect of alcoholic and acetous fermentation on the phytochemicals of Kei apple. The fruit has increased concentrations of l-malic, ascorbic, and phenolic acids among other compounds. Juice was co-inoculated with Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc) to induce alcoholic fermentation (AF). Acetous fermentation followed AF, using an acetic acid bacteria (AAB) consortium. RESULTS: Saccharomyces cerevisiae + Sp wines and vinegars had the highest pH. Total acidity, soluble solids and l-malic acid decreased during AF and acetous fermentation, and was highest in Sc wines and vinegars. Volatile acidity (VA) concentration was highest in Sp vinegars but was not significantly different from Sc and Sc + Sp vinegars. Gallic acid was highest in Sp wines and vinegars, whereas syringic acid was highest in Sc wines and vinegars. The Sc + Sp wines were highest in caffeic, p-coumaric, and protocatechuic acids. Schizosaccharomyces pombe vinegars were highest in caffeic and p-coumaric acids. Highest concentrations of ferulic and sinapic acids were found in Sp and Sc wines, respectively. Chlorogenic acid was most abundant phenolic acid in both wines and vinegars. CONCLUSION: Saccharomyces cerevisiae + Sp and Sc fermentation had a positive effect on most phenolic acids; Sc + AAB had an increased effect on syringic and chlorogenic acids, whereas Sp + AAB resulted in an increase in gallic, caffeic, and p-coumaric acids. The AAB selected had minimal performance with respect to VA production in comparison to commercial vinegars. Acetic acid bacteria selection for acetous fermentation should therefore be reconsidered and the decrease of certain phenolic acids during acetous fermentation needs to be investigated. © 2021 Society of Chemical Industry.

The impacts of Schizosaccharomyces on winemaking.

In the past century, yeasts from the genus Saccharomyces represented the only option in fermentation industries, such as winemaking, to produce wine, beer, and other fermented products. However, other genera are currently emerging to solve challenges in modern enology. Schizosaccharomyces pombe is showing promising results in solving specific challenges in northern, cool viticulture regions with highly acidic wines by deacidifying these wines through its malic acid metabolism. In addition, this microorganism is considered beneficial in warm growing regions with challenges such as the control of wine food safety problems such as the presence of biogenic amines, ochratoxin A, or ethyl carbamate. Indeed, the genus Schizosaccharomyces positively influences other important wine quality parameters, such as color and polysaccharide content. However, the main challenge of using this genus remains the selection of proper strains that alleviate problems such as the production of high acetate concentrations. Industries other than wine production such as ginger fermentation, apple wine, Kei-apple fermentation, plum wine, sparkling wine, and bilberry fermentation industries have also started to study Schizosaccharomyces species as an alternative tool for solving specific related problems. The review discusses the influence of Schizosaccharomyces on different fermentation quality parameters and its main applications in different industries.

Effects on varietal aromas during wine making: a review of the impact of varietal aromas on the flavor of wine.

Although there are many chemical compounds present in wines, only a few of these compounds contribute to the sensory perception of wine flavor. This review focuses on the knowledge regarding varietal aroma compounds, which are among the compounds that are the greatest contributors to the overall aroma. These aroma compounds are found in grapes in the form of nonodorant precursors that, due to the metabolic activity of yeasts during fermentation, are transformed to aromas that are of great relevance in the sensory perception of wines. Due to the multiple interactions of varietal aromas with other types of aromas and other nonodorant components of the complex wine matrix, knowledge regarding the varietal aroma composition alone cannot adequately explain the contribution of these compounds to the overall wine flavor. These interactions and the associated effects on aroma volatility are currently being investigated. This review also provides an overview of recent developments in analytical techniques for varietal aroma identification, including methods used to identify the precursor compounds of varietal aromas, which are the greatest contributors to the overall aroma after the aforementioned yeast-mediated odor release.

The impact of Torulaspora delbrueckii yeast in winemaking.

Commercial Saccharomyces strains are usually inoculated to ferment alcoholic beverages due to their ability to convert all fermentable sugars into ethanol. However, modern trends in winemaking have turned toward less known, non-Saccharomyces yeast species. These species perform the first stages of natural spontaneous fermentation and play important roles in wine variety. New alcoholic fermentation trends have begun to consider objectives other than alcohol production to improve flavor diversity. This review explores the influence of the most used and commercialized non-Saccharomyces yeast, Torulaspora delbrueckii, on fermentation quality parameters, such as ethanol, glycerol, volatile acidity, volatile profile, succinic acid, mannoproteins, polysaccharides, color, anthocyanins, amino acids, and sensory perception.

The impacts of Lachancea thermotolerans yeast strains on winemaking.

At one time, Saccharomyces spp. yeasts were the only option for use in winemaking due to their unique abilities to metabolize all grape juice sugars to ethanol. However, during the previous decade, several commercial non-Saccharomyces yeast products appeared in the biotechnology market. Some of them have slowly begun to establish new enological resources to solve modern winemaking challenges in the new century. Among these challenges, acidification in the warm-growing regions is of great concern for improving wine quality from those areas, particularly in light of the predictions of serious climate change. This review explores one of the most popular commercialized non-Saccharomyces yeast options in warm viticultural regions, Lachancea thermotolerans, and its influences on wine quality parameters, such as lactic acid, ethanol, glycerol, volatile acidity, volatile profiles, isovaleric acid, mannoproteins, polysaccharides, color, anthocyanins, amino acids, and sensory perception.

Analytical impact of Metschnikowia pulcherrima in the volatile profile of Verdejo white wines.

Most wine aroma compounds, including the varietal fraction, are produced or released during wine production and derived from microbial activity. Varietal aromas, typically defined as terpenes and thiols, have been described as derived from their non-volatile precursors, released during wine fermentation by different yeast hydrolytic enzymes. The perception of these minority aroma compounds depends on the chemical matrix of the wine, especially on the presence of majority aroma compounds, such as esters or higher alcohols. Strategies aiming to reduce the production of these masking flavors are on the spotlight of enology research as a way to better define varietal standard profiles for the global market. Using a natural white must from Verdejo variety (defined as a thiol grape variety), here we describe the analytical and sensorial impact of using, in sequential inoculations, a selected strain of Metschnikowia pulcherrima, in combination with two different Saccharomyces cerevisiae strains. An increase in the levels of the thiol 4-MSP (4-methyl-4-sulfanylpentan-2-one) over its sensory threshold, together with a decrease in higher alcohol production, was observed when M. pulcherrima was used. This has an important impact on these wines, making them fruitier and fresher, always preferred by the sensory panel.

Use of non-Saccharomyces yeasts and oenological tannin in red winemaking: Influence on colour, aroma and sensorial properties of young wines.

Today, many non-Saccharomyces strains have been verified can be positive for the development of wine anthocyanin and aroma in different fermentation scenarios. Moreover, oenological tannins are widely used in wine industry to improve the colour profile and aroma complexity. The aim of this work is to analyze the fermentation characters of non-Saccharomyces strains and investigate the effects of pre-fermentative addition of oenological tannins on the wine components as well as sensory properties. For this purpose, five selected non-Saccharomyces strains and grape seed tannin were used to carry out the different fermentation trials. As a result, the grape seed tannin were less likely to influence growth kinetics of non-Saccharomyces strains. Schizosaccharomyces pombe has been proved can be effective to reduce the malic acid content while increase the level of vinylphenolic pyranoanthocyanin, which is positive for wine colour stability. Pre-fermentative use of oenological tannin was verified could be beneficial for the wines fermented with non-Saccharomyces regarding the improvement of wine colour, anthocyanin composition and the complexity of volatile compounds. Nevertheless, sensory analysis showed that oenological tannin could be less effective to modify the aroma impression of non-Saccharomyces wines.

The Combined Use of Schizosaccharomyces pombe and Lachancea thermotolerans-Effect on the Anthocyanin Wine Composition.

The most popular methodology to make red wine is through the combined use of Saccharomyces cerevisiae yeast and lactic acid bacteria, for alcoholic fermentation and malolactic fermentation respectively. This classic winemaking practice produces stable red wines from a microbiological point of view. This study aims to investigate a recent red winemaking biotechnology, which through the combined use of Lachancea thermotolerans and Schizosaccharomyces pombe is used as an alternative to the classic malolactic fermentation. In this new methodology, Schizosaccharomycespombe totally consumes malic acid, while Lachancea thermotolerans produces lactic acid, avoiding excessive deacidification of musts with low acidity in warm viticulture areas such as Spain. This new methodology has been reported to be a positive alternative to malolactic fermentation in low acidity wines, since it has the advantage to produce wines with a more fruity flavor, less acetic acid, less ethyl carbamate originators and less biogenic amines than the traditional wines produced via conventional fermentation techniques. The study focuses on unexplored facts related to this novel biotechnology such as color and anthocyanin profile.

Outlining the influence of non-conventional yeasts in wine ageing over lees.

During the last decade, the use of innovative yeast cultures of both Saccharomyces cerevisiae and non-Saccharomyces yeasts as alternative tools to manage the winemaking process have turned the oenology industry. Although the contribution of different yeast species to wine quality during fermentation is increasingly understood, information about their role in wine ageing over lees is really scarce. This work aims to analyse the incidence of three non-Saccharomyces yeast species of oenological interest (Torulaspora delbrueckii, Lachancea thermotolerans and Metschnikowia pulcherrima) and of a commercial mannoprotein-overproducer S. cerevisiae strain compared with a conventional industrial yeast strain during wine ageing over lees. To evaluate their incidence in mouthfeel properties of wine after 4 months of ageing, the mannoprotein content of wines was evaluated, together with other wine analytic parameters, such as colour and aroma, biogenic amines and amino acids profile. Some differences among the studied parameters were observed during the study, especially regarding the mannoprotein concentration of wines. Our results suggest that the use of T. delbrueckii lees in wine ageing is a useful tool for the improvement of overall wine quality by notably increasing mannoproteins, reaching values higher than obtained using a S. cerevisiae overproducer strain. Copyright © 2016 John Wiley & Sons, Ltd.

Combined Use of S. pombe and L. thermotolerans in Winemaking. Beneficial Effects Determined Through the Study of Wines' Analytical Characteristics.

The most common way to produce red wine is through the use of Saccharomyces cerevisiae strains for alcoholic fermentation and lactic acid bacteria for malolactic fermentation. This traditional winemaking methodology produces microbiologically stable red wines. However, under specific conditions off-flavours can occur, wine quality can suffer and human health problems are possible, especially after the second fermentation by the lactic acid bacteria. In warm countries, problems during the malolactic fermentation arise because of the high pH of the must, which makes it very difficult to properly control the process. Under such conditions, wines with high acetic acid and histamine concentrations are commonly produced. This study investigates a recent red wine-making technology that uses a combination of Lachancea thermotolerans and Schizosaccharomyces pombe as an alternative to the conventional malolactic fermentation. This work studies new parameters such as aroma compounds, amino acids, ethanol index and sensory evaluation. Schizosaccharomyces pombe totally consumes malic acid while Lachancea thermotolerans produces lactic acid, avoiding excessive deacidification of musts with low acidity in warm viticulture areas. This methodology also reduces the malolactic fermentation hazards in wines with low acidity. The main products are wines that contain less acetic acid, less biogenic amines and precursors and less ethyl carbamate precursors than the traditional wines produced via conventional fermentation techniques.

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.

Quality and Composition of Airén Wines Fermented by Sequential Inoculation of Lachancea thermotolerans and Saccharomyces cerevisiae.

This study evaluates the influence of Lachancea thermotolerans on low-acidity Airén grape must from the south of Spain. For this purpose, combined fermentations with Lachancea thermotolerans and Saccharomyces cerevisiae were compared to a single fermentation by S. cerevisiae. Results of all developed analyses showed significant differences in several parameters including acidity, population growth kinetics, concentration of amino acids, volatile and non-volatile compounds, and sensorial parameters. The Airén wine quality increased mainly due to the acidification by L. thermotolerans. The acidification process caused a lactic acid increment of 3.18 g/L and a reduction of 0.22 in pH compared to the control fermentation, performed by S. cerevisiae.

Dynamic analysis of physiological properties of Torulaspora delbrueckii in wine fermentations and its incidence on wine quality.

This work examines the physiology of a new commercial strain of Torulaspora delbrueckii in the production of red wine following different combined fermentation strategies. For a detailed comparison, several yeast metabolites and the strains implantation were measured over the entire fermentation period. In all fermentations in which T. delbrueckii was involved, the ethanol concentration was reduced; some malic acid was consumed; more pyruvic acid was released, and fewer amounts of higher alcohols were produced. The sensorial properties of final wines varied widely, emphasising the structure of wine in sequential fermentations with T. delbrueckii. These wines presented the maximum overall impression and were preferred by tasters. Semi-industrial assays were carried out confirming these differences at a higher scale. No important differences were observed in volatile aroma composition between fermentations. However, differences in mouthfeel properties were observed in semi-industrial fermentations, which were correlated with an increase in the mannoprotein content of red wines fermented sequentially with T. delbrueckii.

Combine Use of Selected Schizosaccharomyces pombe and Lachancea thermotolerans Yeast Strains as an Alternative to the Traditional Malolactic Fermentation in Red Wine Production.

Most red wines commercialized in the market use the malolactic fermentation process in order to ensure stability from a microbiological point of view. In this second fermentation, malic acid is converted into L-lactic acid under controlled setups. However this process is not free from possible collateral effects that on some occasions produce off-flavors, wine quality loss and human health problems. In warm viticulture regions such as the south of Spain, the risk of suffering a deviation during the malolactic fermentation process increases due to the high must pH. This contributes to produce wines with high volatile acidity and biogenic amine values. This manuscript develops a new red wine making methodology that consists of combining the use of two non-Saccharomyces yeast strains as an alternative to the traditional malolactic fermentation. In this method, malic acid is totally consumed by Schizosaccharomyces pombe, thus achieving the microbiological stabilization objective, while Lachancea thermotolerans produces lactic acid in order not to reduce and even increase the acidity of wines produced from low acidity musts. This technique reduces the risks inherent to the malolactic fermentation process when performed in warm regions.The result is more fruity wines that contain less acetic acid and biogenic amines than the traditional controls that have undergone the classical malolactic fermentation.

The Influence of Chitosan on the Chemical Composition of Wines Fermented with Lachancea thermotolerans.

Chitosan exerts a significant influence on various chemical parameters affecting the quality of wine produced using multiple strains of Lachancea thermotolerans. The impact of chitosan on these parameters varies depending on the specific strain studied. We observed that, under the influence of chitosan, the fermentation kinetics accelerated for all examined strains. The formation of lactic acid increased by 41% to 97% across the studied L. thermotolerans strains, depending on the specific strain. This effect also influenced acidity-related parameters such as total acidity, which increased by 28% to 60%, and pH, which experienced a decrease of over 0.5 units. The consumption of malic acid increased by 9% to 20% depending on the specific strain of L. thermotolerans. Nitrogen consumption also rose, as evidenced by all L. thermotolerans strains exhibiting a residual value of Primary Amino Nitrogen (PAN) of below the detection limit, and ammonia consumption increased by 90% to 100%, depending on the strain studied. However, certain parameters such as acetic acid, succinic acid, and glycerol showed contradictory results depending on the strain under investigation. In terms of volatile composition, chitosan supplementation led to increased production of i-butanol by 32% to 65%, 3-methylbutanol by 33% to 63%, and lactic acid ethyl ester by 58% to 91% across all studied strains of L. thermotolerans. Other analyzed aroma compounds exhibited varying changes depending on the specific strain of L. thermotolerans.

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.

Microsatellite typing of Lachancea thermotolerans for wine fermentation monitoring.

Climate change is causing a lack of acidity during winemaking and oenologists use several solutions to cope with such a problem. Lachancea thermotolerans, which has the potential to tolerate the harsh physicochemical conditions of wine, has emerged as a promising alternative for pH management during winemaking and, currently, it is the most valuable yeast used for acidity control in wine. In this work a manageable method for L. thermotolerans genotyping based on a multiplexed microsatellite amplification in 6 different loci was developed. The proposed method was used to distinguish between 103 collection strains obtained from different geographical and isolation sources, and then challenged against a 429 L. thermotolerans isolates from several wineries and harvests. The procedure was also tested for fermentation monitoring and strain implantation. This approach was conceived to simplify the methodology available for L. thermotolerans genotyping, making it easy for applying in wine-related laboratories. This method can be applied to distinguish between L. thermotolerans strains in selection programs and to follow implantation of inoculated strains during winemaking with optimal results.

Impact of Thermophysical Properties of High-Alloy Tool Steels on Their Performance in Re-Purposing Applications.

Resource efficiency and circularity in the context of sustainability are rapidly gaining importance in the steel industry. One concept regarding circular economy is "repurposing". In the context of this work, worn-out machine circular knives are used to produce new chisels for woodturning. The chisels can be extracted parallel or perpendicular to the rolling direction of the primary production process, resulting in an associated carbide orientation of the repurposed tool. The rolling direction, and therefore carbide alignment, will influence the wear resistance and the thermophysical properties, whereby the thermal conductivity will determine the temperatures at the tip of the chisel. Therefore, the thermal conductivity was investigated with the dynamic measurement method, where the specific heat capacity, density and thermal diffusivity of the extracted chisels and industrial reference chisels were measured separately. Moreover, the electrical resistivity was measured in order to calculate the electronic thermal conductivity according to the Wiedemann-Franz-Lorenz law. It was shown that all of these parameters exhibited different degrees of variability with rising temperature. In a detailed analysis, the thermal diffusivity could be identified as an essential parameter of thermal conductivity. By taking two conventional chisels with different chemical compositions and heat treatments into account, it can be seen that the microstructure determines the thermophysical properties. Considering the carbide direction, the chisels that were extracted parallel to the rolling direction showed differing thermophysical properties. Therefore, the carbide orientation is shown to play a significant role regarding the heat dissipation at the cutting edge, because differences, especially in the electronic thermal conductivity in the parallel and perpendicular extracted chisels, can be measured. In addition to the wear resistance factor, the thermal conductivity factor now also supports the removal of the repurposed chisels parallel to the rolling direction.