Yeast dynamics in the black table olives processing using fermented brine as starter

Spontaneous fermentation with autochthonous yeasts is the most traditional method used for the production of black table olives, which requires minimal intervention. The aim of this study was to evaluate the effects of adding a brine starter, developed from one-year spontaneously fermented black table olives, on the microbiological, chemical, and sensory characteristics of naturally fermented Taggiasca table olives. The olives were fermented in brine containing 12% (w/v) NaCl with 0.6% (w/v) citric acid and inoculated with a selected brine starter containing primarily Pichia manshurica (87% predominance) and Saccharomyces cerevisiae (10% predominance). Brine and olives samples were analysed at the start of the experiment and after 3, 6, 9, and 12 months of fermentation. The P. manshurica and S. cerevisiae present in the brine starter drove the entire fermentation process, along with other autochthonous species that were not included in the starter, including Zygosaccharomyces mrakii. Spoilage microorganisms and undesired off-odours and off-flavours were not present at the end of fermentation. When compared to the control, the use of the brine starter increased the total yeast population in the brine during the first 6 months of fermentation, thus shortening the debittering time of the fruits and improving the taste complexity of the final product.

YEAST DYNAMICS AND PHYSIOCHEMICAL EVALUATION OF CARROT WINE PRODUCED WITH Saccharomyces cerevisiae

Yeast dynamics and physiochemical evaluation of carrot wine produced with Saccharomyces cerevisiae were assessed. Fresh ripe and health carrot (6kg) were sequentially processed (washed, preheated, blended and sieved) into juice and fermented for 60 days with Saccharomyces cerevisiae. Airtight glass jars composed of juice (2000g), distilled water (2000mL) and sugar (200g) at controlled temperature (20 -25 0C) was used for fermentation. Wines were clarified (siphoning), aged (45 days) and pasteurized (500C – 600C) to stop fermentation. Proximate analysis, yeast dynamics, physiochemical and wine qualities were assessed. Result showed that juice extraction process reconstitute nutritional composition of carrot, such that moisture, ash and total carbohydrates increased, while others (fat, crude fiber and crude protein) decreased. A trendy progressive yeast dynamic model of Yeast load = -0.195 (Day) 2 + 1.822 (Day) + 4.566 with coefficient (R² = 0.907) was observed. Fermentation significantly decreased pH and increased total acidity. Observed wine qualities include alcoholic content (7.88 - 9.19%v/v), attenuation (121% - 142%) and calories (0%). Clarification and ageing have diminishing effect on alcohol content. Carrot wine was judged as physically appealing moderate alcoholic beverage, with smooth consistent taste (authors' opinion), and could be modeled with yeast dynamics. Thus this wine is recommended to calories sensitive people.

Oenological potential of non-Saccharomyces yeasts to mitigate effects of climate change in winemaking: impact on aroma and sensory profiles of Treixadura wines

ABSTRACT The effects of climate change on wine include high-alcohol content, low acidity and aroma imbalance. The potential of several non-Saccharomyces wine yeasts to mitigate these effects was evaluated by sequential fermentation of Treixadura grape must. Fermentations with only Saccharomyces cerevisiae ScXG3 and a spontaneous process were used as control assays. All yeast strains were obtained from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (EVEGA), Galicia, Spain. Fermentation kinetics as well as yeast dynamics and implantation ability varied depending on inoculated yeasts. In addition, the results showed significant differences in the chemical composition of wine. Starmerella bacillaris 474 reduced the alcohol content (1.1% vol) and increased the total acidity (1.2 g L−1) and glycerol of wines. Fermentation with Lachancea thermotolerans Lt93 and Torulaspora delbrueckii Td315 also decreased the alcohol content, although to a lesser extent (0.3% and 0.7% vol, respectively); however, their effect on wine acidity was less significant. The wines also differed in their concentration of volatile compounds and sensory characteristics. Thus, wines made with Metschnikowia fructicola Mf278 and S. cerevisiae ScXG3 had higher content of esters, acetates and some acids than other wines, and were most appreciated by tasters due to their fruity character and overall impression.

The Influence of Fungicide Treatments on Mycobiota of Grapes and Its Evolution during Fermentation Evaluated by Metagenomic and Culture-Dependent Methods

The present study evaluated the impact of organic and conventional fungicide treatments compared with untreated samples (no fungicides were used) on the grape berry yeast community of the Montepulciano variety. The yeast dynamics during the spontaneous fermentation using culture-dependent and -independent methods was also evaluated. Results showed a reduction of yeast biodiversity by conventional treatments determining a negative influence on fermenting yeasts in favor of oxidative yeasts such as Aerobasidium pullulans. Starmerella bacillaris was significantly more present in organic samples (detected by next generation sequencing (NGS)), while Hanseniaspopa uvarum was significantly less present in untreated samples (detected by the culture-dependent method). The fermenting yeasts, developed during the spontaneous fermentation, were differently present depending on the fungicide treatments used. Culture-dependent and -independent methods exhibited the same most abundant yeast species during the spontaneous fermentation but a different relative abundance. Differently, the NGS method was able to detect a greater biodiversity (lower abundant species) in comparison with the culture-dependent method. In this regard, the methodologies used gave a different picture of yeast dynamics during the fermentation process. The results indicated that the fungal treatments can influence the yeast community of grapes leading must fermentation and the final composition of wine.