Yeast mannoproteins released during the process of aging wine on the yeast lees have been reported to make important contributions to wine quality. However, few mannoproteins have been identified in wine and their lifespan during aging is unknown. As a first step towards better understanding the contributions of yeast mannoproteins to wine quality, a model system was used to follow changes in yeast protein release, and to identify the released proteins over a 9-month time course following completion of fermentation. Model musts were fermented in duplicate by a number of commercial yeast strains, including BM45 and RC212, and were stored on the yeast lees post-fermentation with monthly stirring at 15°C. Wine samples were taken during and after fermentation, and following removal of suspended solids, total protein and total mannoproteins were measured, and individual proteins were identified--but not quantified--by HPLC-MS of tryptic fragments. The total number of identified proteins in all samples increased from between 3-15 following inoculation, to between 70-80 after one month on the lees, and decreased to about 20 after 6 months on the lees. Over 50% of the identified proteins were shared among all yeast samples. For most strains, protein and mannoprotein concentrations increased during, but decreased by the end of fermentation. Both protein and mannoprotein concentrations were found to increase again post-fermentation, reaching values about 2- and 6-fold higher than values measured at 2 days, respectively. Consistent with the increase in mannoprotein concentration, cell wall mannoproteins were the predominant proteins identified after 6 months of aging on the lees. Most cytosolic proteins found during and soon after fermentation were not found after 6 months of aging on the lees. / Graduation date: 2009