Biotransformation of Volatiles in Fermented Osmanthus (Osmanthus fragrans) Flowers by Yeast

Abstract

Sweet osmanthus (Osmanthus fragrans) is a species of flowering plants in Asia prized for food, flavor and fragrance industries. This work studied biotransformation of volatiles in osmanthus flowers through monoculture fermentation of infusions of sweet osmanthus flowers using yeasts, Saccharomyces cerevisiae and Williopsis saturnus. The major volatiles in two osmanthus cultivars Jingui and Yingui before and after fermentation were terpenoids and ketones. Esters, alcohols and acetic acid were only present after fermentation, and aldehydes were largely depleted after fermentation. The volatile profile of sweet osmanthus flowers fermented with S. cerevisiae was described as sweet and floral, while that of sweet osmanthus flowers fermented with W. saturnus was fruity, sweet and floral. Addition of nutrients (glucose and diammonium phosphate) increased alcohol and ester production, decreased percentage reduction of ketones and terpenes. Biotransformation of terpenes varied with each compound and fermentation treatment. Overall, yeast fermentation proved to be effective in enhancing sweet osmanthus flower fragrance for production of unique essential oils from this invaluable flower.