Turning ameliorates the quality of cocoa bean-like product from the seed of fermented rambutan (Nephelium lappaceum L.) fruit

Rambutan fruits are glutted on the market during the harvest season. Much of them are wasted as they are highly perishable. To reduce wastage, fermentation coupled with turning could be employed. In this study, rambutan fruits were fermented for 8 days at different turning intervals (no turning, turning at every 24, 48, and 72 hr). The properties of the fermented seed and microbiological profile of the fruit fermentation were determined. The findings showed that turning at every 48 hr is recommended to produce well-fermented seed with high cut test score (927.5) and fermentation index (1.393). Lactic acid bacteria were found to dominate the microbial community throughout the fermentation, and their maximum count (8.9 log CFU/g seed-pulp mass) was observed after 24 hr of fermentation. Together with other desirable characteristics, the fermented seed could be transformed into a cocoa powder-like product by roasting the seed postfermentation, just like a cocoa bean. Novelty impact statement The present study showed that turning of rambutan fruits at every 48 hr is recommended in order to produce well-fermented seeds which subsequently could be produced into a cocoa powder-like product by roasting the seed postfermentation in a manner similar to that of cocoa bean roasting. This is a seminal report that reveals the microbial succession of rambutan fruit fermentation and showed that 8 days of fermentation is required to not only produce well-fermented seeds but also eliminate the pathogenic microorganisms found in the fruits. These findings could provide new insights to the industries that work on new food product development and have an aim to fully utilize the rambutan fruit, including its seed.