[Retention of volatile organic compounds in a freeze-dried model food gel (author's transl)].

In this work the results obtained during freeze-drying of a food model gel are reported. The model system was constituted by 12,5% sucrose, 2,5% pectin and five organic volatile substances: acetone, ethyl acetate, methanol, ethanol and n-propanol. In particular, it was studied the effect of granulation and the effect of frozen material thickness on retention of volatiles. Other experiments were made to study volatiles distribution inside the freeze-dried materials; the stripping action of warm air and of water vapor flux through the freeze-dried layers, and eventually the holding capacity of dried layers to "capture" the volatiles. All the data suggested a theory about the different mechanisms which influence the retention and the remotion of volatiles during freeze-drying of foods.