containing 15 g of substrate (dry weight basis) and covered with eight layers of gauze. For all experiments, initial conditions were: temperature, 30°C; pH, 6; inoculum size, 1 × 107 spores/g dry matter (d.m.), and initial water content, 70% (v/w) (maximum absorp- tion of the substrate). Experiments were performed to study the effect of glucose addition (20, 35 and 46 g/100 g d.m.) on the production of volatile compounds, and also the effect of addition of some possible precursors: leucine (10 mmol), soya bean oil (10% v/w)) and a saline solution, previously optimized [19]. All experi- ments were conducted in three sets.