In view of climate change and the increasingly antagonistic wine market, the exploitation of native genetic resources is revisited in relation to sustainable wine production. ‘Sideritis’ is a late-ripening Greek grape variety, which is quite promising for counteracting wine quality issues associated with the annual temperature rise. The aim of this study was to improve the quality and to enhance the aroma of ‘Sideritis’ wine through the use of native yeasts. To improve vinification, Hanseniaspora opuntiae L1 was used along with Saccharomyces cerevisiae W7 in mixed fermentations (SQ). The addition of H. οpuntiae significantly altered the chemical profile of the wine compared to the single-inoculated fermentations with W7 (IS). H. opuntiae increased all the acetate esters, except for hexyl acetate and (Z)-3-hexen-1-ol acetate. The concentration of 2-phenylethyl acetate, which imparts flowery and sweet notes, exhibited a 2.6-fold increase in SQ as compared to IS wines. SQ also showed higher levels in several ethyl esters, including ethyl butyrate, ethyl heptanoate and ethyl 7-octenoate, which are associated with fruity notes compared to IS. H. opuntiae produced citronellol, a terpene associated with rose and green notes, and increased the overall acceptance of the wine. Present results are thus quite promising for improving ‘Sideritis’ wine quality towards a sustainable wine production in Greece in view of global warming.

Non-Saccharomyces (NS) yeasts are gaining popularity in modern winemaking for improving wine quality. Climate change is one of the biggest challenges winegrowing now faces in warm regions. Here, Lachancea thermotolerans LtS1 and Torulaspora delbrueckii TdS6 combined with Saccharomyces cerevisiae ScS13 isolated from Assyrtiko grapes from Santorini island were evaluated in grape must fermentation with the aim to mitigate major consequences of temperature rise. Different inoculation protocols were evaluated, including simultaneous and sequential mixed-strain inoculations, displaying significant variation in the chemical and kinetic characteristics. Both LtS1 and TdS6 could raise the titratable acidity (TA). TdS6 also reduced the volatile acidity (VA) and was thus chosen for further evaluation in microvinifications and pilot-scale fermentations. Consistent with lab-scale trials, sequential inoculation exhibited the longest persistence of TdS6 resulting in minimum VA levels. Diethyl succinate, ethyl propanoate, and ethyl isobutyrate were significantly increased in sequential inoculations, although a decline in the net total ester content was observed. On the other hand, significantly higher levels of TA, succinic acid, and 2-methylpropanoic were associated with sequential inoculation. The overall performance of TdS6 coupled with a high compatibility with S. cerevisiae suggests its use in the fermentation of Santorini-Assyrtiko or other high sugar musts for the production of structured dry or sweet wines.

Autochthonous Saccharomyces cerevisiae vineyard populations are important components of the grape/wine system. Besides their direct impact on winemaking, they also constitute an untapped reservoir of genotypes with special technological attributes for the wine industry. Research so far on S. cerevisiae populations has focused on spatial distribution on large scales, yet little is known about the genetic variability of populations within viticultural zones and their temporal genotypic variation. Here, S. cerevisiae populations from different vineyards in Santorini, a small Aegean island, were genotyped and their genetic diversity was assessed within and between vineyards during two consecutive years. Despite the relative geographical isolation of the island, a relatively high genetic diversity was uncovered. The vast majority of genotypes were vineyard-specific, while in one of the vintages, significant differences in the genotypic composition of vineyards were detected. Overall, higher differences were detected between vintages rather than among vineyards. Notably, only four genotypes were common for the two vintages, three of which were commercial S. cerevisiae strains, probably “escapees” from wineries. Nevertheless, the populations of the two vintages were not genetically distinct. Present results highlight the magnitude of genetic diversity in natural wine yeast populations on a small spatial scale, yet the invasion of commercial starters may constitute a potential risk for loss of local yeast biodiversity. However, present results show that industrial strains do not necessarily dominate over the natural strains or their high abundance may be temporary.

A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 2⁴ screening design was built to investigate the main factors affecting the extraction of volatile components, namely the volume of extraction solvent, sonication time, salt content, and pH. Then, the factors with significant effects were optimized using an I-optimal design. The optimal value for all the variables studied was reached under the following experimental conditions: volume of extraction solvent 200 μL and salt content 5% m/v. The suitability of the optimized method was evaluated, resulting in very good linearity with coefficients of determination (R²) higher than 0.995 in all cases, while repeatability was lower than 8.4% except for d-limonene and p-cymene. Recoveries higher than 82% were observed for the groups of ethyl esters, acetate esters, alcohols, and terpenoid alcohols (linalool, α-terpineol). The recovery of acids ranged from 70.5% to 88.9%, whereas the three monoterpenes studied (d-limonene, γ-terpinene, p-cymene) were not extracted satisfactorily. The proposed method was effectively applied for the analysis of volatile compounds in laboratory-scale fermentations with selected strains of Saccharomyces cerevisiae.