(-)Geosmin sorption by enological yeasts in model wine and FTIR spectroscopy characterization of the sorbent

For the first time, we report that enological yeasts or yeast cell walls can sorb (-)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l(-1)). The wine is described as earthy or mouldy. The influence of various post-harvesting processes on yeast (-)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals which may explain the different sorption capacities. The possible involvement of phospholipids in (-)geosmin sorption by yeasts highlights the complexity of this phenomenon. The post-harvesting processes were: spray-drying, mechanical cell disruption, autolysis and two methods of rehydration of dried yeast samples. The results show that, using the optimal combination of processes, the initial (-)geosmin concentration in model wine can be decreased by more than 50%. (C) 2009 Elsevier Ltd. All rights reserved.