Evaluation of the native microflora of grapes in the viticultural region of Ştefan Vodă

Abstract

Fermentative yeasts are used industrially in the production of wine, having as their main characteristic the ability to produce the fermentation of simple carbohydrates in anaerobiosis, with the formation of ethyl alcohol and carbon dioxide. A large number of microorganisms are found, in particular, during the ripening period of the grapes. In the autumn, after harvesting, the yeasts on the leaves fall into the soil with their fall, being there until the spring, thus taking place natural selection, as a result of which the most resistant species survive. The purpose of the research consisted in the application of microbiological methods and techniques for the observation, isolation and identification of microorganisms existing in the examined products to establish the presence or absence of harmful microorganisms, especially the determination of the indigenous microflora. The study methods focused on the direct microscopy of the washing water of Cabernet Sauvignon and Merlot grapes from Javgur, Cimișlia district and the inoculation of microorganisms on media by scarification, after which the media were placed in a thermostat at a temperature of 30 ºC and maintained for 7 days. The inoculation was carried out on the following media: Sabouraud (SDA), MRS (sterilized), Broth, Bretanomyces Agar. After the microscopy of the grape-washing waters, the presence of Saccharomyces yeasts and rod-shaped acetic bacteria was detected in both samples. The presence of the following microorganisms was also found: on the Sabouraud medium - yeasts from the genus Saccharomyces cerevisiae and Torulopsis, and the Bretanomyces agar medium - the genus Bretanomyces. Thus, we could deduce that the grapes from the studied region have yeasts of the Saccharomyces genus, which would allow the fermentation to be carried out on wild yeasts and would ensure a reduction in expenses and other benefits, but in addition to the fermentation yeasts in the analyzed grape samples, there were also detected other types of yeasts and even bacteria that could pose a danger to the fermentation process. Further research will focus on ways to capitalize on the indigenous microflora of grapes in the above-mentioned area. The authors thank the Project for Young Researchers 23.70105.5107.04T Valorization of the indigenous flora of the Ștefan Vodă wine-growing region to increase the authenticity and competitiveness of Moldovan wines, which is carried out within the Oenological Research Center, Department of Oenology and Chemistry, Faculty of Food Technology, Technical University of Moldova.