Using Torulaspora delbrueckii, Saccharomyces cerevisiae and Saccharomyces bayanus wine yeasts as starter cultures for fermentation and quality improvement of mead

Integration of LC-HRMS and 1H NMR metabolomics data fusion approaches for classification of Amarone wine based on withering time and yeast strain

Two untargeted metabolomics approaches (LC-HRMS and 1H NMR) were combined to classify Amarone wines based on grape withering time and yeast strain. The study employed a multi-omics data integration approach, combining unsupervised data exploration (MCIA) and supervised statistical analysis (sPLS-DA). The results revealed that the multi-omics pseudo-eigenvalue space highlighted a limited correlation between the datasets (RV-score = 16.4%), suggesting the complementarity of the assays. Furthermore, the sPLS-DA models correctly classified wine samples according to both withering time and yeast strains, providing a much broader characterization of wine metabolome with respect to what was obtained from the individual techniques. Significant variations were notably observed in the accumulation of amino acids, monosaccharides, and polyphenolic compounds throughout the withering process, with a lower error rate in sample classification (7.52%). In conclusion, this strategy demonstrated a high capability to integrate large omics datasets and identify key metabolites able to discriminate wine samples based on their characteristics.

Kinetic Evaluation of the Production of Mead from a Non-Saccharomyces Strain

There is a growing market for craft beverages with unique flavors. This study aimed to obtain a palate-pleasing mead derived from Pichia kudriavzevii 4A as a monoculture. Different culture media were evaluated to compare the fermentation kinetics and final products. The crucial factors in the medium were ~200 mg L-1 of yeast assimilable nitrogen and a pH of 3.5-5.0. A panel of judges favored the mead derived from Pichia kudriavzevii 4A (fermented in a medium with honey initially at 23 °Bx) over a commercial sample produced from Saccharomyces cerevisiae, considering its appearance, fruity and floral flavors (provided by esters, aldehydes, and higher alcohols), and balance between sweetness (given by the 82.91 g L-1 of residual sugars) and alcohol. The present mead had an 8.57% v/v ethanol concentration, was elaborated in 28 days, and reached a maximum biomass growth (2.40 g L-1) on the same fermentation day (6) that the minimum level of pH was reached. The biomass growth yield peaked at 24 and 48 h (~0.049 g g-1), while the ethanol yield peaked at 24 h (1.525 ± 0.332 g g-1), in both cases declining thereafter. The Gompertz model adequately describes the kinetics of sugar consumption and the generation of yeast biomass and ethanol. Pathogenic microorganisms, methanol, lead, and arsenic were absent in the mead. Thus, Pichia kudriavzevii 4A produced a safe and quality mead with probable consumer acceptance.

Key Odorants Forming Aroma of Polish Mead: Influence of the Raw Material and Manufacturing Processes

Mead was analyzed by using the concept of molecular sensory science for the identification of key odorants. A total of 29 odor-active compounds were identified in mead by using gas chromatography olfactometry (GCO). Flavor dilution (FD) factors of identified compounds ranged from 1 to 16,384, compounds with FD factors ≥32 were quantitated by using stable isotopically substituted odorants as internal standards or external standard method, and odor activity values (OAVs) were calculated. Fifteen compounds showed OAVs ≥1: aldehydes (2-phenylacetaldehyde, 3-(methylsulfanyl)propanal), 4-hydroxy-3-methoxybenzaldehyde), esters (ethyl 3-methylbutanoate, ethyl propanoate, ethyl octanoate), alcohols (2-phenylethan-1-ol, 3- and 2-methylbutan-1-ol, 3-(methylsulyfanyl)propan-1-ol), furanons (4-hydroxy-2,5-dimethylfuran-3(2H)-one, 3-hydroxy-4,5-dimethylfuran-2(5H)-one), acids (3- and 2-methylbutanoic acid, acetic acid), 1,1-diethoxyethane, and 4-methylphenol. 2-Phenylacetaldehyde (OAV, 3100) was suggested as the compound with the biggest influence on the aroma of mead, followed by 4-hydroxy-2,5-dimethylfuran-3(2H)-one (OAV, 1900), 3-(methylsulfanyl)propanal (OAV, 890), and 2-phenylethan-1-ol (OAV, 680). Quantitative olfactory profile analysis revealed strong honey, malty, and alcoholic impressions. Omission experiments revealed that 3-(methylsulfanyl)propanal, 2-phenylethan-1-ol, 4-hydroxy-2,5-dimethylfuran-3(2H)-one, ethyl propanoate, ethyl 3-methylbutanoate, 2-phenylacetaldehyde, 3- and 2-methylbutanoic acid, 3-hydroxy-4,5-dimethylfuran-2(5H)-one, and 4-hydroxy-3-methoxybenzaldehyde were the key odorants in the mead. Determining concentrations of key odorants in important production steps showed that the fermentation and maturation stages had the strongest effect on the formation of mead aroma.

Effects of Torulaspora delbrueckii and Saccharomyces cerevisiae Co-Fermentation on the Physicochemical and Flavor Compounds of Huaniu Apple Cider

The effects of different fermentation methods utilizing Torulaspora delbrueckii 1004 and Saccharomyces cerevisiae 32169 on the physicochemical properties, organic acid content, polyphenol and flavonoid concentrations, antioxidant activity, and volatile aroma compounds of Huaniu apple cider were investigated in this study. Employing methods of single inoculation, co-inoculation, and sequential inoculation, it was found that sequential fermentation exhibited strong fermentative power in the initial stages, effectively reducing the content of soluble solids and achieving a balanced composition of malic, succinic, and citric acids while maintaining a lower titratable acidity. Sequential inoculation was observed to significantly enhance the total polyphenols and flavonoids, as well as the antioxidant capacity (p < 0.05). Specifically, in the synthesis of volatile aroma compounds, sequential inoculation significantly enhanced the richness and diversity of the Huaniu apple cider's aromas, particularly in terms of the concentration of ester compounds (p < 0.05). Principal component analysis further confirmed the superiority of sequential inoculation in terms of aroma component diversity and richness. The findings of this study suggest that sequential inoculation of fermentation with non-Saccharomyces and S. cerevisiae is an effective strategy for optimizing the flavor characteristics of Huaniu apple cider, offering valuable theoretical support and practical guidance for enhancing cider quality and fostering the development of new products.

Reviewing the Source, Physiological Characteristics, and Aroma Production Mechanisms of Aroma-Producing Yeasts

Flavor is an essential element of food quality. Flavor can be improved by adding flavoring substances or via microbial fermentation to impart aroma. Aroma-producing yeasts are a group of microorganisms that can produce aroma compounds, providing a strong aroma to foods and thus playing a great role in the modern fermentation industry. The physiological characteristics of aroma-producing yeast, including alcohol tolerance, acid tolerance, and salt tolerance, are introduced in this article, beginning with their origins and biological properties. The main mechanism of aroma-producing yeast is then analyzed based on its physiological roles in the fermentation process. Functional enzymes such as proteases, lipases, and glycosidase are released by yeast during the fermentation process. Sugars, fats, and proteins in the environment can be degraded by these enzymes via pathways such as glycolysis, methoxylation, the Ehrlich pathway, and esterification, resulting in the production of various aromatic esters (such as ethyl acetate and ethyl caproate), alcohols (such as phenethyl alcohol), and terpenes (such as monoterpenes, sesquiterpenes, and squalene). Furthermore, yeast cells can serve as cell synthesis factories, wherein specific synthesis pathways can be introduced into cells using synthetic biology techniques to achieve high-throughput production. In addition, the applications of aroma yeast in the food, pharmaceutical, and cosmetic industries are summarized, and the future development trends of aroma yeasts are discussed to provide a theoretical basis for their application in the food fermentation industry.

Contribution of Saccharomyces and Non-Saccharomyces Yeasts on the Volatile and Phenolic Profiles of Rosehip Mead

The resurgence of mead, a honey-based fermented beverage, is attributed to the increasing consumption of fermented foods and beverages, driven by its distinct flavors and perceived health benefits. This study investigates the influence of different yeast strains, namely Saccharomyces cerevisiae var. bayanus, and Torulaspora delbrueckii, on the volatile and phenolic compounds of these beverages. Analytical techniques, including HPLC-DAD and GS/MS, were employed to analyze the chemical composition of the beverages. ANOVA analysis of variance was conducted to assess differences in the volatile and phenolic compounds. The findings reveal that yeast selection significantly impacts the chemical profiles of the beverages. Saccharomyces cerevisiae fermentation preserves rosehip-specific flavonoids and phenolic acids. Sequential fermentation with Torulaspora delbrueckii demonstrated proficiency in generating esters, contributing to fruity and floral aromas in the beverages. This study investigates the importance of yeast selection in shaping the chemical composition of rosehip mead, providing insights into the distinct characteristics conferred by different yeast strains. By optimizing yeast selection and fermentation techniques, the overall quality and diversity of these beverages can be enhanced.

Chemical and sensory characterization of coffee from Coffea arabica cv. Mundo Novo and cv. Catuai Vermelho obtained by four different post-harvest processing methods

BACKGROUND

After the harvest, green coffee beans are dried on the farm using several methods: the wet process, natural process, pulped natural process, or mechanical demucilaging. This study evaluated how the choice of a specific processing method influenced the volatile organic compounds of the coffee beans, before and after roasting, and the sensory characteristics of the beverage. Coffea arabica beans of two varieties (cv. Mundo Novo and cv. Catuai Vermelho) were subjected to these four processing methods on a single farm in the Cerrado area of Brazil.

RESULTS

Analysis by gas chromatography-mass spectrometry headspace solid-phase microextraction identified 40 volatile organic compounds in green coffee beans and 37 in roasted beans. The main difference between post-harvest treatments was that naturally processed green beans of both varieties contained a different profile of alcohols, acids, and lactones. In medium-roasted beans, those differences were not observed. The coffee beverages had similar taste attributes but distinct flavor profiles. Some of the treatments resulted in specialty-grade coffee, whereas others did not.

CONCLUSION

The choice of a specific post-harvest processing method influences the volatile compounds found in green beans, the final beverage's flavor profile, and the cupping score, which can have a significant impact on the profitability of coffee farms' operations. © 2022 Society of Chemical Industry.

Analyzing the minor volatilome of Torulaspora delbrueckii in an alcoholic fermentation

Torulaspora delbrueckii is an emerging yeast species in the beverage and food industry that is suitable for alcoholic fermentation and to improve the organoleptic quality of wine, beer, mead, and other beverages. Modern consumer preference toward new flavors and products drives the application of T. delbrueckii to ferment less traditional fruits and vegetables. Thus, it has become increasingly relevant to define those metabolites produced in minute quantities by T. delbrueckii, because they may have an impact when producing these new alcoholic beverages. In this study, we have identified metabolites of T. delbrueckii and have compared them with those of Saccharomyces cerevisiae in a controlled setting with a synthetic, high glucose medium using gas chromatography coupled to flame ionization detector (GC–FID) and stir bar sorptive extraction (SBSE) with GC coupled to mass spectrometry (MS). Results showed that T. delbrueckii produced metabolites with higher changes in odor activity complexes than S. cerevisiae: ethyl propanoate, 1,1-diethoxyethane, ethyl isobutyrate, ethyl butyrate, isoamyl acetate, ethyl heptanoate, nonanal, and decanal. We also report seven metabolites detected for the first time in T. delbrueckii. This datum serves to expand the knowledge of T. delbrueckii performance and shows that application of this yeast species is more suitable to a wide array of beverage producers.

Effects of different yeast strains, nutrients and glutathione-rich inactivated yeast addition on the aroma characteristics of Catarratto wines

Catarratto is one of the most common non-aromatic white grape varieties cultivated in Sicily (Southern Italy). In order to improve the aromatic expression of Catarratto wines a trial was undertaken to investigate the effect of yeast strain, nutrition and reduced glutathione. Variables included two Saccharomyces cerevisiae strains, an oenological strain (GR1) and one isolated from honey by-products (SPF52), three different nutrition regimes (Stimula Sauvignon Blanc™ (SS), Stimula Chardonnay™ (SC) and classic nutrition practice), and a specific inactivated yeast rich in reduced glutathione to prevent oxidative processes [Glutastar™ (GIY)] ensuing in ten treatments (T1-T10). Microbiological and chemical parameters demonstrated the aptitude of strain SPF52 to successfully conduct alcoholic fermentation. During fermentation, the Saccharomyces yeast populations ranged from 7 to 8 logarithmic CFU/mL. All wines had a final ethanol content ranging between 12.91 and 13.85% (v/v). The dominance of the two starter strains over native yeast populations was higher than 97% as estimated by interdelta analysis. The addition of nutrients SS or SC increased the aromatic complexity of the wines as reflected by volatile organic compounds (VOCs) composition and sensory profiles. In particular, 32 VOCs were identified; alcohols (62.46-81.1%), thiols (0.27-0.87%), ethers (0.09-0.16%), aldehydes (0-1.21%), ketones (0-2.28%), carboxylic acids (4.21-12.32%), esters (0-10.85%), lactones (0.9-1.49%) and other compounds (0.77-6.9%). Sensory analysis demonstrated a significant impact on wine aroma in relation to yeast starter strain used, the type of nutrition (SS, SC or classic nutrition) and the presence/absence of GIY. The wines produced with GR1 yeast strain and SS (T2), SPF52 with SC (T9) both in presence of GIY showed higher overall quality. Trials T2 and T9 showed the highest scores for 13 and 18 attributes, respectively. The different nutrition, addition of GIY and the yeast starter strains diversified and enhanced sensory expression of Catarratto wines.