Yeasts associated to Malbec grape berries from Mendoza, Argentina

Aims: The aims of this work were to evaluate different pre-isolation treatments applied to complete yeast extraction from grapes and to identify the yeast microflora associated to Malbec grapes from two vineyards located in Mendoza, Argentina. Methods and Results: The pre-isolation treatments evaluated were shaking, jet streaming with pressurized water and grape blending. The overall results clearly indicated that when a more vigorous and disruptive pre-isolation treatment was applied; larger numbers of yeast species were recovered. The yeast population on healthy and ripe Malbec grapes was in the order of 10(5)-10(6) CFU g(-1). Eight different yeast species were isolated from berries, including Kloeckera apiculata, Metschnikowia pulcherrima, Pichia membranifaciens, Saccharomycodes ludwigii, Candida species (Candida stellata and Candida raghi), Issatchenkia orientalis and Rhodotorula spp. Conclusions: Grape blending gave the highest yeast counts. Rainfall near grape harvest time quantitatively and qualitatively modifies the yeast microflora. The yeast species identified on ripe grapes from the Mendoza region, partially match those previously documented in different parts of the world related. S. ludwigii has not been previously reported in grapes. Significance and Impact of the Study: The report is on yeast microbiota in grapes from Mendoza, Argentina. Saccharomycodes ludwigii was found in high percentage (17%), this species has not been described before on grapes surface. The importance of pre-isolation steps to the recovery of high number of yeasts was shown. Influence of climatic conditions near harvest time on microflora was confirmed.