Fermentation of grape must by sequential association of yeasts: Accumulation of pyruvic and α-ketoglutaric acid

Fermentations of grape (cv. Malvar) musts from two consecutive vintages were carried out using the autochthonous microflora, a sequential association of yeasts and conventional fermentations with addition of sulfur dioxide to the must. The pyruvic and α‐ketoglutaric acid content over the course of fermentation was measured and showed that for both vintages tested the maximum accumulation of the ketoacid pyruvic acid took place several days earlier in fermentations using a sequential association of yeasts than in conventional fermentations. The accumulation of pyruvic acid was higher in the must made from grapes with a higher degree of ripening and the lowest level of added SO2. In the fermentations using either a sequential association of yeasts or the autochthonous microflora with no added SO2, accumulation of α‐ketoglutaric acid was higher in the must with the higher nitrogen content when the species making the greatest percentage contributions at the start of fermentation presented high levels of proteolytic activity.