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The cider market has been significantly expanding and gaining momentum in Eastern Europe. As such, the aim of this study was to obtain sparkling cider via the Champenoise method using two Romanian apple varieties (Topaz and Red Topaz) alongside the employment of two fermentations. Four yeast strains were used in the first fermentation, while encapsulated Saccharomyces cerevisiae was used in the second fermentation. The resulting cider was subjected to a comprehensive investigation to quantitatively determine the carbohydrates, organic acids, volatile and phenolic compounds, and amino acids from all the cider samples. A trained panel evaluated the sensory profile of the samples, and a chemometric analysis was used to interpret the data. Secondary fermentation increased the accumulation of malic acid and lactic acid, as well as the volatile profile complexity. The total polyphenol content in the sparkling cider samples increased by almost 20% in the S. cerevisiae sample and over 217% in the P. kluyveri + S. cerevisiae sample compared to the base cider. Additionally, studying the production and consumption trends of sparkling cider offers valuable insights for both producers and consumers. By understanding consumer preferences and refining production techniques, the industry can deliver higher-quality products that better align with market demands. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The conformational properties of hydrolysates derived from brewer's spent grain protein (BSGP) pretreatment with and without ultrasound were investigated, and the effect of BSGP hydrolysate (BSGPH) supplementation on the brewer's yeast growth and fermentation performances were examined. Results demonstrated that BSGPH had substantial influences on the biomass, viability, sugar consumption, and ethanol production of yeast. Specifically, medium supplemented with hydrolysates derived from BSGP pretreated with ultrasound (UBPH) for 4-h hydrolysis (UBPH-4) increased biomass by 7.7%, viability by 9.78%, sugar consumption by 37.16%, and ethanol yields by 20.20% (v/v), respectively, compared with the blank. UBPH-4 exhibited a looser morphology and disordered secondary structure, with a decrease in α-helix and increased random coil. Meanwhile, a higher proportion of short peptides and hydrophilic amino acids in UBPH-4 might account for its preferred bioactivity. All findings revealed that UBPH were effective nitrogen sources for yeast growth and fermentation. [ABSTRACT FROM AUTHOR]

Three peptides (LL, LML, and LLL) were used to examine their influences on the osmotic stress tolerance and cell wall properties of brewer's yeast. Results suggested that peptide supplementation improved the osmotic stress tolerance of yeast through enhancing the integrity and stability of the cell wall. Transmission electron micrographs showed that the thickness of yeast cell wall was increased by peptide addition under osmotic stress. Additionally, quantitative analysis of cell wall polysaccharide components in the LL and LLL groups revealed that they had 27.34% and 24.41% higher chitin levels, 25.73% and 22.59% higher mannan levels, and 17.86% and 21.35% higher β-1,3-glucan levels, respectively, than the control. Furthermore, peptide supplementation could positively modulate the cell wall integrity pathway and up-regulate the expressions of cell wall remodeling-related genes, including FKS1, FKS2, KRE6, MNN9, and CRH1. Thus, these results demonstrated that peptides improved the osmotic stress tolerance of yeast via remodeling the yeast cell wall and reinforcing the structure of the cell wall. Key points: • Peptide supplementation improved yeast osmotic stress tolerance via cell wall remodeling. • Peptide supplementation enhanced cell wall thickness and stability under osmotic stress. • Peptide supplementation positively modulated the CWI pathway under osmotic stress. [ABSTRACT FROM AUTHOR]

The influences of three wheat gluten peptides (WGP-LL, WGP-LML, and WGP-LLL) on the osmotic stress tolerance and membrane lipid component in brewer's yeast were investigated. The results demonstrated that the growth and survival of yeast under osmotic stress were enhanced by WGP supplementation. The addition of WGP upregulated the expressions of OLE1 (encoded the delta-9 fatty acid desaturase) and ERG1 (encoded squalene epoxidase) genes under osmotic stress. At the same time, WGP addition enhanced palmitoleic acid (C16:1) content, unsaturated fatty acids/saturated fatty acids ratio, and the amount of ergosterol in yeast cells under osmotic stress. Furthermore, yeast cells in WGP-LL and WGP-LLL groups were more resistant to osmotic stress. WGP-LL and WGP-LLL addition caused 25.08% and 27.02% increase in membrane fluidity, 22.36% and 29.54% reduction in membrane permeability, 18.38% and 14.26% rise in membrane integrity in yeast cells, respectively. In addition, scanning electron microscopy analysis revealed that the addition of WGP was capable of maintaining yeast cell morphology and reducing cell membrane damage under osmotic stress. Thus, alteration of membrane lipid component by WGP was an effective approach for increasing the growth and survival of yeast cells under osmotic stress. Key points: •WGP addition enhanced cell growth and survival of yeast under osmotic stress. •WGP addition increased unsaturated fatty acids and ergosterol contents in yeast. •WGP supplementation improved membrane homeostasis in yeast at osmotic stress. [ABSTRACT FROM AUTHOR]

Apple cider production is a complex fermentation process that involves the conversion of apple juice into cider through the actions of yeast and malolactic bacteria. This study aimed to investigate the effects of the co-inoculation of Saccharomyces and non- Saccharomyces yeasts, as well as nutrient supplementation in the presence of malolactic bacteria Oenoccocus oeni on the composition of apple cider. The amino acid profile of the samples was not significantly influenced by the addition of lactic bacteria or nutrients in cider processing. The highest ester content was recorded in the single yeast strain fermented ciders (55.32%–88.13%). This increase was visible also for the malolactic ciders, independent from nutrient supplementation. Co-inoculated Saccharomyces and Torulaspora delbrueckii ciders showed increased higher alcohols contents, both after the alcoholic (42.66%–53.51%) and malolactic fermentations (42.81%–65.94%). Following the hydroxycynnamic acids class (141.47–327.44 mg/L), flavonoids (114.81–253.44 mg/L) were the second most abundant class of phenolic compounds in ciders, which generally registered a considerable increase following malolactic fermentation. The sour/acidic taste was the most prevalent sensory attribute of the cider. Lower values were recorded for sweet, bitter, and astringent. The strongest apple aroma was perceived in the co-inoculated Saccharomyces and T. delbrueckii yeast strains. The co-fermentation of Saccharomyces and Torulaspora delbrueckii yeasts led to increased levels of desirable aroma compounds, contributing to a more complex and appealing sensory profile, while the nutrient supplementation provided an improved malolactic fermentation efficiency and overall cider quality. [Display omitted] • Microbiological and biochemical factors influencing cider composition were studied. • Highest ester content recorded in the single yeast strain fermented ciders. • Flavonoids registered a considerable rise following malolactic fermentation. • The sour/acidic taste was the most prevalent sensory attribute of the cider. • The strongest apple aroma was perceived in the co-inoculated Saccharomyces and T. delbrueckii yeast strains. [ABSTRACT FROM AUTHOR]

The effects of wheat gluten hydrolysates (WGH) and their ethanol elution fractions obtained on XAD-16 resin on physiological activity and fermentation performance of brewer's yeast during very-high-gravity (VHG) worts fermentation were investigated. The results showed that the addition of WGH and their elution fractions in VHG worts significantly enhanced yeast biomass and viability, and further increased the fermentability, ethanol yield and productivity of yeast. Supplementation with 40% ethanol fraction exhibited the highest biomass (6.9 g/L dry cell), cell viability, fermentability (82.05%), ethanol titer (12.19%, v/v) and ethanol productivity during VHG worts fermentation. In addition, 40% ethanol fraction supplementation also caused the most consumption of amino acid and the highest accumulation of intracellular glycerol and trehalose, 15.39% of increase in cell-membrane integrity, 39.61% of enhancement in mitochondrial membrane potential (MMP), and 18.94% of reduction in intracellular reactive oxygen species (ROS) level in yeast under VHG conditions. Therefore, WGH supplementation was an efficient method to improve fermentation performance of brewer's yeast during VHG worts. [ABSTRACT FROM AUTHOR]

Summary: The ethanol fermentation efficiency was affected by multiple stress tolerance of yeast during brewing and bioethanol industry. The effect of KCl on the multiple stress tolerance of yeast cells was examined. Results showed that KCl addition significantly enhanced the tolerance of yeast cells to osmotic and ethanol stress, which correlated with the decreased membrane permeability, the increased intracellular ergosterol and ATP content, and the improved activity of complex II and complex III in yeast cells. Biomass and viability of yeast cells under osmotic and ethanol stress were increased significantly by KCl addition. Supplementation of 4 and 10 g L−1 KCl exhibited the best promotion activity for yeast cells present in medium with 500 g L−1 sucrose and 10% (v v−1) ethanol, respectively. These results suggested that exogenous potassium addition might be an effective strategy to improve yeast tolerance and fermentation efficiency during industrial very‐high‐gravity (VHG) fermentation. [ABSTRACT FROM AUTHOR]

Wheat gluten hydrolysates (WGH) and KCl were used to examine their effects on fermentation performances and physiological characteristics of brewer's yeast during very high gravity (VHG) fermentation. Results showed that all supplementations exhibited a notable promotion in yeast growth, glucose utilization, ethanol production, and physiological characteristics. Combination supplementation of 0.3% WGH and 0.5% KCl showed the best promotion effect with 6.38%, 9.41% and 8.68% of increases in biomass, glucose utilization and ethanol production, respectively. Moreover, combination addition of WGH and KCl also enhanced significantly membrane integrity and mitochondrial functionality of brewer's yeast. Amino acid compositions of WGH and intracellular metabolites analysis indicated that active nitrogen metabolism and high levels of stress resistant substances might be responsible for the improvement of growth and fermentation performances in brewer's yeast by nutrient supplementation. • WGH and KCl supplementations promoted cell growth and fermentation of yeast. • WGH and KCl addition improved membrane integrity and mitochondrial functionality. • Combination of 0.3% WGH and 0.5% KCl showed the best bioactivity for yeast. • Active nitrogen metabolism and stress resistant substances were related to activity. [ABSTRACT FROM AUTHOR]