Fruity aroma production in solid state fermentation by Ceratocystis fimbriata: influence of the substrate type and the presence of precursors

Wheat bran, cassava bagasse and sugar cane bagasse were shown to be adequate substrates for the growth and aroma production by the mould Ceratocystis fimbriate. Among the nutritive media tested, sugar cane bagasse complemented with a synthetic medium containing glucose (200 g l(-1)) gave a fruity aroma while the leucine or valine-containing medium gave a strong banana aroma. Aroma production was dependent on growth and the maximum aroma intensity was detected at about the time of the maximum respirometric activity. Twenty-four compounds have been separated by GC headspace analysis and 20 were identified, among them: 1 aldehyde, 7 alcohols, 4 ketones and 8 esters. It was dearly demonstrated that the chromatographic profile of the headspace of the culture was dependent on the substrate used and on the eventual precursor added. When leucine or valine was added to the substrate, the production of total volatiles in the headspace reached values up to tenfold higher than that for ripe bananas. The Gompertz model, a logistic-like equation, was used to fit the integrated CO2 and volatiles production data.