Hawaii's Chocolate Bug: Investigating Drosophila melanogaster as an inoculant for small-scale cacao fermentation

Abstract

Currently, Hawai'i cacao production is performed on a small scale. Fermentation is an essential step when developing the flavor of the chocolate. Much of the fermented cacao that is being produced in Hawai'i does not maintain the quality that is required to generate a premium product. Small-scale cacao producers in Hawaii are challenged by low quality, low ambient temperature fermentation due to small batch size. Hawai'i producers are not currently using any form of controlled microbial inoculant. It is also highly desirable to process cacao more quickly and produce more reliable results. In this experiment, fruit flies (Drosophila melanogaster) were cultured in the lab and applied to small-scale ferments to assess the viability of applying fruit flies as an inoculant in order to improve small-scale cacao fermentation. Five treatments were applied to cacao beans. Treatments consisted of two populations of whole flies shaken in distilled water, two populations ground in distilled water, and a hand/ambient air inoculation. Dried bean samples were assessed with a dry bean cut test and total aerobic bacteria populations and total yeast populations with Petrifilm™ plates. In general, population 2, whole fly dilutions, had the highest average colony count of anaerobic bacteria per cm2, and hand/ambient inoculation had the highest average colony count of yeast/mold per cm2. Population 2 also performed the most effectively in a cut bean test, with only 20% undesirable beans. These results indicate the further investigation of inoculants for small-scale cacao fermentation is necessary.