Three molecules potentially useful as natural food flavouring substances, in accordance with EEC directives, were isolated from a culture of Pichia membranaefaciens. The optimal culture conditions were found to be a yeast extract and glucose base at a pH between 5.0 and 6.0 and at an incubation temperature of 30 degrees-35 degrees C. Flavouring substances were identified as propanoic acid ethyl ester, acetic acid 3-methlybutyl ester and butyl ethyl ether by HRGC/MS. This is the first report of butyl ethyl ether in a natural matrix.1117579