Effet des agents protecteurs sur la survie des cultures concentrees de Geotrichum candidum durant la lyophilisation et l'entreposage

The effect of protective agents on the survival of concentrated cultures of Geotrichum candidum after freeze-drying and during storage was studied. Initially, the effect of three disaccharides (trehalose, sucrose and maltose), alone or combined with skim milk, was compared to the control (skim milk only) immediately after freeze-drying at various temperatures. In a second time, the survival of G. candidum during storage was studied in relation to the physical stability of the protective agents. The results showed that freeze-drying temperature does not affect the survival of G. candidum immediately after freeze-drying; however, a difference was observed during storage; survival was proportional to the concentration of the protective agents; skim milk alone did not offer a good survival to the G. candidum cultures; however when combined with the protective agents, a clear improvement was noted. The glass transition temperature (Tg) of the protective agents, significantly dependent on the water content, could contribute to predict the stability of G. candidum during storage.