There is a lack of studies evaluating the metabolic contribution of non-Saccharomyces yeasts in early fermentation phases. This study aimed to investigate the volatile aroma profiles produced by various non-Saccharomyces yeasts just before sequential inoculation with Saccharomyces cerevisiae to provide an insight into the particular effects they induce at this stage. The grape must of Malvazija istarska was inoculated with monocultures of Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia kluyveri, Lachancea thermotolerans, and Schizosaccharomyces pombe, alongside a S. cerevisiae control. Eighty volatile compounds were quantified via headspace solid-phase microextraction and gas chromatography–mass spectrometry, and the data were statistically elaborated. Volatile profiles of non-Saccharomyces yeasts differed significantly from the S. cerevisiae control. Most treatments caused increases in linalool and β-damascenone, decreases in higher alcohols and fatty acids, and improved synthesis of odoriferous esters. Torulaspora delbrueckii and M. pulcherrima produced compounds not commonly found in S. cerevisiae fermented wines. Multivariate statistical analysis linked the investigated yeasts to specific, particularly abundant compounds. Future studies should explore to what degree these contributions persist after sequential inoculation with S. cerevisiae in diverse grape must matrices.

The yeast Lachancea thermotolerans has the ability to produce notable amounts of lactic acid and reduce alcoholic strength in fermentation, so it has a considerable potential for mitigating negative impacts of climate changes in winemaking. In this study, a treatment with L. thermotolerans and Saccharomyces cerevisiae in sequential inoculation was compared to a control S. cerevisiae monoculture fermentation of Malvazija istarska (aka Malvasia Istriana) white grape must. Standard physico-chemical parameters of the obtained wines were determined by the OIV methods. Targeted (GC/FID and GC/MS) and untargeted (GC×GC/TOF-MS) gas chromatographic techniques were combined for the analysis of volatile compounds. Phenolic compounds were analyzed by UPLC/QqQ-MS/MS, and proteins by RP-HPLC-DAD, while a sensory analysis of wines was performed by a panel of trained and certified tasters. L. thermotolerans co-fermentation treatment increased the concentration of lactic acid and decreased alcoholic strength. L. thermotolerans increased the concentrations of geraniol, β-ionone, isobutanol, isobutyric acid, ethyl isobutyrate, several major acetates, ethyl lactate, and diethyl succinate, followed by many minor compounds. This wine also contained more hydroxycinnamoyl tartrates, while control S. cerevisiae wine had higher levels of free hydroxycinnamates. The effects on PR proteins were minor. L. thermotolerans co-fermentation slightly enhanced the sensory perception of tropical fruit, herbaceous, tobacco, and buttery odor notes, as well as fullness of body. With the largest number of identified volatile compounds up to date and other results obtained, this study contributes to the better understanding of oenological and especially aromatic potential of L. thermotolerans in white wine production.

Despite its promising potential, the capabilities of Saccharomyces paradoxus in commercial winemaking are still unutilized and require further investigation. In this study, the effects of fermentation by a S. paradoxus strain P01-161 on the composition of Malvazija istarska white wine in two harvest years were investigated. A range of complementary standard and metabolomics analysis approaches were applied, including OIV methods for basic parameters; HPLC-DAD-RI for organic acids, glycerol, and proteins; UPLC/MS/MS for phenolic compounds; and GC/FID, GC/MS, and GC × GC/TOF-MS for volatile compounds. The harvest year exhibited a significant impact, but many distinctive traits of S. paradoxus versus S. cerevisiae control wines were consistent across the seasons. These included reductions in malic acid and certain phenols and pathogenesis-related proteins. Saccharomyces paradoxus fermentation yielded higher levels of glycerol, volatile acidity, and specific thaumatin-like proteins. Among a total of 474 identified volatile compounds, S. paradoxus exhibited lower concentrations of several odoriferous alcohols, acids, and esters, as well as higher concentrations of β-damascenone, acetaldehyde, isobutyric acid, ethyl 2-methylbutyrate, ethyl acetate, isobutyl acetate, various esters of succinic and lactic acids, accompanied by numerous minor compounds, when compared to S. cerevisiae. These differences suggest the potential for distinct sensory profiles produced by the two yeasts, indicating that S. paradoxus could be a promising alternative for white wine production.

Bentonites used for wine clarification vary widely in their ability to remove proteins and alter wine composition, yet the role of their intrinsic properties remains unclear. To address this, eight commercial bentonites with diverse physico-chemical characteristics were analyzed. The doses required for complete protein removal and stabilization were determined and then applied to clarify a Malvazija istarska (Vitis vinifera L.) white wine. Clarified wines were compared with one another and with a non-clarified control using ICP-OES for elemental composition, HPLC-DAD for phenolic compounds, and HS-SPME-GC/MS for volatile compounds. Protein removal efficiency correlated positively with Na/Ca ratio, cation exchange capacity, swelling capacity, negative ζ-potential, and internal specific surface area, and negatively with particle size and external specific surface area. Sodium and calcium showed the greatest increases in wine concentrations. Effects on individual low-molecular-weight phenols were inconsistent, though all bentonites removed a fraction of total phenols. Volatile compounds, particularly esters, were significantly reduced. When compared on a per-gram basis, bentonites that were more efficient in protein removal also showed greater removal of phenols and volatile compounds; however, at full application doses, many of these differences diminished or reversed. Overall, the study advances understanding of bentonite–wine interactions and supports more informed selection of bentonites in oenological practice.

To gain a broad understanding of yeast species' effects, Malvazija istarska wines produced by sequential inoculation with five non-Saccharomyces starters and monoculture fermentation with a Saccharomyces cerevisiae×S. paradoxus hybrid and a S. cerevisiae control were thoroughly analyzed. Two-dimensional gas chromatography/mass spectrometry, alongside conventional GC, enabled the identification of 399 volatile compounds and revealed many yeast-specific effects. Non-Saccharomyces starters generally decreased the concentrations of acetaldehyde, 2-phenylethanol, fatty acids, and volatile phenols, while increasing the concentrations of isobutanol, its esters, and isoamyl acetate. Torulaspora delbrueckii had the most pronounced impact, with higher concentrations of short-chain ethyl esters and acetates, and lower levels of acetaldehyde, medium-chain acids, and their ethyl esters. The effects on terpenoids, norisoprenoids, thiols, C₆-alcohols, ketones, lactones, and furanoids varied. Multivariate analysis revealed numerous yeast-specific volatile markers. Non-Saccharomyces yeasts preserved more hydroxycinnamic acids. Overall, the results obtained provided an in-depth insight into the yeast-driven modulation of white wine chemical composition.