The Influence of Yeast Strain on Whisky New Make Spirit Aroma

Flavour in Scotch malt whisky is a key differentiating factor for consumers and producers alike. Yeast (commonly Saccharomyces cerevisiae) metabolites produce a significant amount of this flavour as part of distillery fermentations, as well as ethanol and carbon dioxide. Whilst yeast strains contribute flavour, there is limited information on the relationship between yeast strain and observed flavour profile. In this work, the impact of yeast strain on the aroma profile of new make spirit (freshly distilled, unmatured spirit) was investigated using 24 commercially available active dried yeast strains. The contribution of alcoholic, fruity, sulfury and sweet notes to new make spirit by yeast was confirmed. Generally, distilling strains could be distinguished from brewing and wine strains based on aroma and ester concentrations. However, no statistically significant differences between individual yeast strains could be perceived in the intensity of seven aroma categories typically associated with whisky. Overall, from the yeast strains assessed, it was found that new make spirit produced using yeast strains marketed as ‘brewing’ strains was preferred in terms of acceptability rating.

Genetic mapping of a bioethanol yeast strain reveals new targets for aldehyde- and thermotolerance

Current technology that enables bioethanol production from agricultural biomass imposes harsh conditions for Saccharomyces cerevisiae's metabolism. In this work, the genetic architecture of industrial bioethanol yeast strain SA-1 was evaluated. SA-1 segregant FMY097 was previously described as highly aldehyde resistant and here also as thermotolerant: two important traits for the second-generation industry. A Quantitative Trait Loci (QTL) mapping of 5-hydroxymethylfurfural (HMF) -resistant segregants of hybrid FMY097/BY4742 disclosed a region in chromosome II bearing alleles with uncommon non-synonymous (NS) single nucleotide polymorphisms (SNPs) in FMY097: MIX23, PKC1, SEA4, and SRO77. Allele swap to susceptible laboratory strain BY4742 revealed that SEA4FMY097 enhances robustness towards HMF, but the industrial fitness could not be fully recovered. The genetic network arising from the causative genes in the QTL window suggests that intracellular signaling TOR (Target of Rapamycin) and CWI (Cell Wall Integrity) pathways are regulators of this phenotype in FMY097. Because the QTL mapping did not result in one major allelic contribution to the evaluated trait, a background effect in FMY097's HMF resistance is expected. Quantification of NADPH - cofactor implied in endogenous aldehyde detoxification reactions - supports the former hypothesis, given its high availability in FMY097. Regarding thermotolerance, SEA4FMY097 grants BY4742 ability to grow in temperatures as high as 38 °C in liquid, while allele PKC1FMY097 allows growth up to 40 °C in solid medium. Both SEA4FMY097 and PKC1FMY097 encode rare NS SNPs, not found in other >1,013 S. cerevisiae. Altogether, these findings point towards crucial membrane and stress mediators for yeast robustness.

New Ciders Made by an Exhaustion Method: An Option to Val-Orise Subproducts from the Making of Ice Ciders

Cryo-extraction (pressing of frozen apples), is one of the two freeze-enrichment systems allowed for the making of ice juices. Its ciders are often described as more complex and aromatic, however, the production yield is quite low. The Exhaustion method associated with the previous one proposes the valorisation of the discarded apple juice fractions for the making of new ciders. Three types of apple juices and three species of yeasts (S. bayanus, C6; S. cerevisiae, Levuline-CHP, and T. delbrueckii, Biodiva-TD291) have been used to evaluate the Exhaustion method. The ciders obtained were analysed for chemical and volatile composition as well as sensory characteristics. The yield (%) of the Exhaustion process ranged between 24 and 37%. The yeasts promoted the fermentation at different rates, providing ciders with alcoholic degrees between 9 and 12 (%v/v), and low volatile acidities. The yeast strain significantly influenced most of the parameters analysed, whereas the raw apple juice influenced the perception of the attributes fruity, apple and butter. Although the ciders produced by Exhaustion presented significantly lower concentrations of all the volatile compounds analysed than the corresponding ice ciders obtained by Cryo-extraction, the S. bayanus C6 and T. delbrueckii TD291 gave highly valued ciders from the sensory point of view.

TAMI-14. REDUCTION IN S. CEREVISIAE GROWTH AND CELL VIABILITY IN RESPONSE TO D-2-HYDROXYGLUTARATE ACCUMULATION IS DAMPENED BY GROWTH CONDITIONS PERMISSIVE OF OXIDATIVE PHOSPHORYLATION

BACKGROUND Elevated levels of D-2-hydroxyglutarate (D2HG) have been detected in several cancers, including IDH1/2 mutant gliomas, PHGDH-amplified breast cancer, diffuse large B-cell lymphomas which harbor loss-of-function mutations in D2HG dehydrogenase gene (D2HGDH), and MYC-amplified breast cancers. Given the high degree of conservation between the yeast and human isocitrate dehydrogenases the similarities between yeast and cancer glycolytic metabolism, we hypothesized that a yeast model would allow for the successful recapitulation of metabolic dysregulation by D2HG. METHODS A heteroallelic idp1 R148H yeast strain was created (equivalent to human IDH2 R172H). The growth characteristics of this strain and the dld3∆ strain (equivalent to D2HGDH loss of function) were evaluated with glucose or galactose carbon source. Octyl-D2HG, a cell permeable mimic of D2HG, was used to assess the effects of D2HG accumulation at varying concentration. FACS was used to measure cell viability, reactive oxygen species (ROS) production, and mitochondrial membrane potential. Analysis of the synthetic lethal genetic array for the dld3∆ strain was performed. RESULTS Accumulation of D2HG in mutant and wild-type yeast strains results in impaired growth and reduction in cell viability in a concentration dependent manner. The negative effect on growth and cell viability is more prominent when cells are not utilizing oxidative phosphorylation for energy production (glucose versus galactose carbon source). D-2HG accumulation results in ROS production in dld3∆ but not in the heteroallelicidp1 R148H yeast strain. An increase in mitochondrial membrane potential occurs in both strains when grown with galactose, but not in glucose. The top negative genetic interactors with dld3∆ include genes involved in mitochondrial function. CONCLUSIONS We found that yeast cells have different sensitivity to the toxic effects of D-2HG depending on the metabolic status of the cell. This suggests that altering cell metabolism may be a viable therapeutic target in cancers with excess production of D2HG such as IDH mutant gliomas.

Volatile Compounds in Monovarietal Wines of Two Amarone Della Valpolicella Terroirs: Chemical and Sensory Impact of Grape Variety and Origin, Yeast Strain and Spontaneous Fermentation

Aroma profiles of withered Corvina and Corvinone wines from two different Valpolicella terroirs were investigated in relationship to yeast strain and use of spontaneous fermentation. The results indicated that volatile chemical differences between wines were mainly driven by grape origin, which was associated with distinctive compositional profiles. Wine content in terpenes, norisoprenoids, benzenoids and C6 alcohols, as well as some fermentative esters, were indeed significantly affected by grape origin. Conversely, yeast strain influence was mainly associated with fermentation-derived esters. Sensory analysis, besides confirming the major role of grape origin as driver of wine differentiation, indicated that spontaneous fermentations reduced the sensory differences associated with grape origin and variety, mainly due to high content of acetic acid and ethyl acetate.

Off-Flavor Removal from Sheep Placenta via Fermentation with Novel Yeast Strain Brettanomyces deamine kh3 Isolated from Traditional Apple Vinegar

Animal placentae can be used as health-promoting food ingredients with various therapeutic efficacies, but their use is limited by their unpleasant odor and taste. This study aimed to investigate the possibility of deodorization of sheep placenta via yeast fermentation. A yeast strain was successfully isolated and identified as a novel Brettanomyces strain (Brettanomyces deamine kh3). The deodorizing efficacy of fermentation of the sheep placenta with B. deamine kh3 was evaluated by 42 panels, based on evaluation of preference, ranking, and aroma profiles, and compared with normal placenta and placenta fermented with B. bruxellensis. The results of the sensory evaluation indicated that fermentation of the sheep placenta with B. deamine kh3 may improve its palatability by increasing flavors such as that of grass (tree), rubber, and burnt, and by decreasing the odor and soy sauce flavor. Solid-phase microextraction-gas chromatography (SPME-GC) showed that major off-flavors in sheep placenta, such as ammonia, dimethyl disulfide, and 1,3-dioxolane, were completely diminished in the sheep placenta fermented with B. deamine kh3. This study presents those major volatile compounds, including 2-isobutyl\-4,4-dimethyl-1,3-dioxane, and 3-methyl-1-butanol, could be crucial in improving the palatability of the sheep placentae fermented with B. deamine kh3. This study provides a good starting point for the industrial application of a new deodorization method.

Influence of Yeast Strain on Odor-Active Compounds in Fiano Wine

The type of yeast strain used for wine alcoholic fermentation dramatically affects its final volatile composition and, therefore, its sensory properties. In this study, the influence of four oenological Saccharomyces strains (three S. cerevisiae and one S. bayanus) on wine volatile composition was determined on the Fiano variety, a typical cultivar from the Campania region (Italy), fermented in oak barrique. Fiano wines were analyzed by means of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/olfactometry (GC/O). The results showed that the four selected yeast strains had a significant impact on the majority of volatile compounds as shown by the concentration of volatile compounds and based on the Aroma Extract Dilution Analysis (AEDA) values for many of the odor volatile compounds. This resulted in a dramatic change of the odor impact of the wines, such as the “fruity” attribute, which was higher compared to the control, and caused some changes of other odor attributes, particularly “floral”, “phenolic” and “honey”. This research demonstrates the potential of using these selected yeast strains and this technological approach of oak fermentation for this typical white wine grape variety.