Effect of fungicides on the yeast population during spontaneous fermentation in the vinification of monastrell grapes

The influence of six fungicides on indigenous yeasts of grape var. Monastrell, after performing two treatments (Good Agricultural Practices-GAP and Critical Agricultural Practices-CAP), was studied. Fungicide residues have been determined using a method of multi-residual extraction that uses QuEChERS and liquid chromatography in tandem with triple quadrupole mass spectrometry. Identification of yeast was carried out by PCR and subsequent sequencing. The fungicide residues are below the EU maximum residue limits (MRLs) established in wine grapes. At the beginning and during the fermentation, most of the treated samples show counts (CFU/mL) higher than the control test (20–30% more), even in the most unfavorable conditions (treated the same day of harvest). It is noteworthy the absence of Hanseniaspora uvarum and the presence of Clavispora lusitaniae, Debaryomyces hansenii and Metschnikowia pulcherrima. Nevertheless, no fungicide either under treatment inhibits fermentation or delays it. Moreover, the evolution of yeast populations found during fermentation follows the normal sequence of species. This research might be of interest for scientists and companies working on either basic or production aspects respectively of the winemaking process.