In extra virgin olive oil (EVOO) extraction process, the occurrence of yeasts that could affect the quality of olive oil was demonstrated. Therefore, in this work, at first, the yeasts occurring during different extractive processes carried out in a Tuscany oil mill, at the beginning, in the middle, and the end of the harvesting in the same crop season, were quantified. Then, possible effects on quality of EVOO caused by the predominant yeast species, possessing specific enzymatic activities, were evaluated. Yeast concentrations were higher in extraction processes at the end of the harvesting. Twelve yeast species showing different isolation frequencies during olive oil extractive process and according to the harvesting date were identified by molecular methods. The yeast species dominating olive oil samples from decanter displayed enzymatic activities, potentially affecting EVOO quality according to zymogram analysis. HS-SPME-GC-MS analysis of the volatile compounds in commercial EVOO, inoculated with three yeast species (Nakazawaea molendini-olei, Nakazawaea wickerhamii, Yamadazyma terventina), pointed out significant differences depending on the strain inoculated. In conclusion, during the olive oil extractive processes, some yeast species colonize the extraction plant and may influence the chemical and sensory characteristics of EVOO depending on the cell concentrations and their enzymatic capabilities.

Aureobasidium pullulans is a yeast-like fungus found on the surface of the grape berries that has been proven to act as a biocontrol agent for the management of grey mould disease caused by Botrytis cinerea. In this work, an indigenous strain of A. pullulans isolated from grape berries and selected according to the in vitro activity against B. cinerea, was used in vineyards of the winery where it originated, in comparison with a commercial product containing two A. pullulans strains with the aim of assessing its effectiveness as a biocontrol agent. The experimental design included daily meteorological data registration and the early defoliation of grapevines as treatments. The monitoring of A. pullulans strains on grape berries by plate counts and molecular methods as well as of B. cinerea symptoms on grape bunches was performed in the different trials from the end of flowering to the harvest time. Results highlighted that although no significant differences (p < 0.05) in the occurrence of B. cinerea were detected according to different treatments, the mean incidence of symptomatic berries ranged from 7 to 16%, with the lowest values recorded in bunches treated with the indigenous A. pullulans strain. The efficacy of the biocontrol agent was affected more by meteorological conditions than the defoliation practice.

This study was aimed to produce pear cider (Perry), using small caliber pears cv Abate Fètel, fermented by Starmerella bacillaris and Saccharomyces cerevisiae in co-inoculated (COF) and sequential (SEF) mixed cultures in comparison with S. cerevisiae monoculture fermentation (AXF), evaluating the influence of yeast starter cultures on Perry characteristics. The perries were re-fermented in bottle by S. cerevisiae strain EC1118. During primary fermentation, growth and fermentation kinetics were different in the co-inoculated and sequential fermentations in comparison with pure S. cerevisiae fermentation; however, sugars were depleted, and 6% (v/v) ethanol was produced in all the trials. Glycerol content was significantly higher in mixed fermentations due to Starm. bacillaris metabolism (+ 20% in COF, and + 42% in SEF conditions). After re-fermentation in bottle, higher levels of 3-Methyl-1-butanol, 1-propanol, acetaldehyde and esters were detected in Perry from the mixed fermentations. All the Perries were accepted by the consumers (general liking values from 6.01 to 6.26). Perries’ appearance from mixed fermentations was described as less intense and more clear. The use of small caliber pears cv Abate Fètel and Starm. bacillaris in combination with S. cerevisiae in Perry production might be a suitable tool to obtain novel beverages with distinctive organoleptic features.

The inoculation of grape juice with Saccharomyces cerevisiae strains selected from indigenous yeast populations can be a suitable tool to control alcoholic fermentation, contributing to producing wines with typical flavor and aroma and, hence, the demand for native starter cultures is increasing. However, since low amounts of indigenous yeast biomasses are usually required for local winemaking, the industrial production of these yeasts can be expensive. Therefore, in this study, after selecting an indigenous S. cerevisiae strain based on relevant oenological and technological features, a pilot-plant for easy and rapid production of fresh yeast biomass directly in a winery located in Tuscany, was exploited. The selected yeast strain was used as a starter to carry out 25 and 100 hL fermentations and its enological performance was compared with that of the commercial starter normally used in the winery. Chemical and sensory analysis of the resulting wines showed that they differentiated according to the used yeast strain, with the wines produced by the indigenous S. cerevisiae strain being characterized by a distinctive aromatic and sensory profile. In conclusion, the pilot-plant effectively resulted in producing fresh yeast starter cultures in the winery to be successfully used to carry out alcoholic fermentations.

The use of earthenware amphorae in winemaking can give wines unique attributes enhancing their typicity. Therefore, in this study, spontaneous and inoculated in-amphora fermentations of Trebbiano Toscano grape must were monitored to assess the Saccharomyces cerevisiae strains occurring in each fermentation as well as the chemical characteristics of the wines. Strain typing via Interdelta analyses pointed out that the commercial starters did not dominate, showing 24% and 13% implantation percentages, and that 20 indigenous strains were present at different percentages, ranging from 2 to 20%, in inoculated and spontaneous fermentations. The assessment of the technical characteristics of the indigenous strains via fermentations at lab and pilot scale (20 L amphorae) and the sensory analysis of the experimental wines allowed for the selection of two indigenous strains to be used as starter cultures in comparison to a commercial strain in 300-L-amphorae vinifications in the cellar. The observed fermentative performances and sensory analysis of the experimental wines highlighted that one indigenous S. cerevisiae strain dominated the process and conferred distinctive sensory characteristics to the Trebbiano Toscano wine, demonstrating its effectiveness in managing the in-amphora fermentations. In addition, the results demonstrated the ability of amphorae to protect the polyphenolic compounds from oxidation during wine ageing. Indeed, the concentration of both hydroxycinnamic acids and flavonols decreased, with an average reduction of 30% and 14%, respectively, while hydroxybenzoic acids remained unchanged.