Application of strains of Geotrichum spp. to decrease higher alcohols and to increase esters

The decrease in the content of higher alcohols and the increase in the ester content in alcoholic drinks are normally achieved by the aging process over years. This study examined the capability of some strains of Geotrichum spp. to complete this process within a few days. Four Geotrichum spp. strains (S12, S13, TM and TF) were separately added to one wine [containing 11.5% (v/v) ethanol] and to three liquor samples [containing 45, 50 and 55% (v/v) ethanol] and incubated at 28 and 15°C for 4 days. Significant increases in the ester content and decreases in the higher alcohols were observed with strains S12 and TM, in all treatments. Strains S13 and TF increased the ester content in the wine, but not in the liquors. Comparatively, most volatile compounds were found in the red wine treated with S12 at 15°C and in the liquor containing 55% (v/v) ethanol treated with TM at 28°C. The conversion from higher alcohols to their corresponding acids and esters was identified using gas chromatography coupled with mass spectrometry during the treatments. By comparing the results when enzyme extracts and whole cells were used, it was found that the decrease in the levels of the higher alcohols might be caused both by cell adsorption and enzymatic reactions, whereas the increase in the esters was caused mainly by enzymatic reactions.