Volatile compounds produced by microorganisms isolated from cork

Microorganisms present on cork (i.e. the reproduction bark of Quercus suber L.) can produce odorous compounds affecting the quality of cork stoppers. This work aims to contribute to the study of the correlation between microbial growth and formation of volatile compounds in the cork. Different strains of microorganisms were cultivated on both malt extract and cork, and the odour of the culture was described by a panel. The volatile compounds were isolated directly from the culture media by a dynamic headspace technique followed by adsorption on to Tenax traps. The volatiles were identified by GC–MS: 63 substances were identified in malt extract cultures, mainly consisting of carbonyl compounds (16), alcohols (16), and sesquiterpenes (13). Cultures on cork produced only 12 volatile compounds, more than half being sesquiterpenes. Sensory evaluation confirmed that cork is an unfavourable culture medium if compared with malt extract.