Biotransformation of durian pulp by mono- and mixed-cultures of Saccharomyces cerevisiae and Williopsis saturnus

Durian is a seasonal tropical fruit widely grown and highly prized in Southeast Asia. This is a first study to assess the transformation of durian constituents during fermentation with mono- and mixed-cultures of Saccharomyces cerevisiae and Williopsis saturnus with a view to developing a novel alcoholic beverage. A diversity of volatiles was produced especially alcohols and esters, while those volatiles initially present in durian, particularly the character-impact sulphur-containing odorants, were transformed. Most of the sulphur-containing compounds decreased with fermentation. 3-(Ethylthio)-1-propanol was produced initially then remained relatively stable, whereas ethyl thioacetate was formed initially then decreased in all culture types. The kinetic changes and concentrations of volatile compounds were similar in both the mixed-culture and the S. cerevisiae monoculture, except for higher amounts of alcohols in the mixed-culture. The W. saturnus monoculture, on the other hand, was the main producer of acetate esters. Sensory evaluation revealed a strong sulphury note retained in all fermentations but less unfavourable metallic and yeasty notes in the mixed-culture. The study suggests that biotransformation by yeasts can be effective in modifying the constituents and modulating the organoleptic properties of durian.

► W. saturnus contributed to mixed-culture fermentation, despite early growth arrest. ► A diversity of volatile compounds was produced particularly esters and alcohols. ► Sulphur-containing compounds in durian were transformed during fermentation. ► Transformation of volatiles varied with the mono- and mixed-cultures. ► Durian pulp fermented by mixed-culture had less undesirable flavour notes.