Natural wines represent a new trend in winemaking without the use of preservatives and starter cultures, revealing the unique quality traits of grapes, wine, and terroir, but are susceptible to spoilage or undesirable fermentations. This study investigated the microbial populations associated with organic
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Natural wines represent a new trend in winemaking without the use of preservatives and starter cultures, revealing the unique quality traits of grapes, wine, and terroir, but are susceptible to spoilage or undesirable fermentations. This study investigated the microbial populations associated with organic grapes, must, and natural wines of the Limniona red grape variety, focusing on different production stages and fermentation vessels. Samples included immature and ripe grapes, initial and fermenting must, filtered and unfiltered wines, and final bottled and filtered wines. These were analyzed in order to enumerate key groups of microorganisms and identify beneficial yeasts and bacteria of alcoholic and malolactic fermentation, respectively, as well as potential markers of off-flavors. Culture-dependent methods were used to enumerate yeasts and bacteria, while Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and 16S rRNA sequencing provided taxonomic resolution. Beneficial fermentation microorganisms (especially
Saccharomyces yeasts) were scarce in initial grapes, where other contaminants or wild yeasts were present. Gradually, as fermentation progressed, there was a prevalence of
Saccharomyces cerevisiae strains of increased diversity in matured wine, as well as several lactic acid bacteria (LAB) of malolactic fermentation. Most LAB were identified as
Lactobacillus and
Oenococcus species. Other bacteria from environmental sources, irrelevant to alcoholic/malolactic fermentation or spoilage, like
Burkholderia, were also present during the vinification process. The type of vessel affected the type of LAB that prevail, with an abundance of
Oenococcus in clay vessels versus
Lactobacillus species in stainless-steel vessels. Notably,
Lentilactobacillus parafarraginis can be linked to off-flavors if they represent a high percentage of the wine microbiota. These findings highlight the importance of understanding, monitoring and controlling microbial succession during production stages in order to prevent sensory faults and ensure the stable quality of natural wines.
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