Coffee residues as substrates for aroma production by Ceratocystis fimbriata in solid state fermentation

Abstract

The ability of two different strains of Ceratocystis fimbriata for fruity aroma production by solid state fermentation (SSF) was tested on coffee pulp and coffee husk complemented with glucose as substrates. Experiments were carried out in 250 mL Erlenmeyer flasks and the experimental conditions were: 70% of initial moisture, 20% of glucose addition and pH 6.0. Aeration was made by passive diffusion through the gauze covering the flasks. Headspace analysis of the culture by gas chromatography (GC) showed that 12 compounds were produced with coffee husk. Maximum total volatiles (TV) concentration was reached after 72 h of culture with coffee husk as substrate (28 μmol.L-1.g -1). Ethyl acetate, ethanol and acetaldehyde were the major compounds produced, representing 84.7%, 7.6% and 2.0% of TV, respectively. A pre-treatment with heat (100°C/40 min) of substrates did not improve TV production. Respirometry analysis was used to determine the growth of the culture by measuring carbon dioxide produced. Results showed that the CO 2 production follows the aroma production. This result shows the great potential for the use coffee pulp and coffee husk as substrates to microbial aroma production by solid state fermentation.