Dynamics of Geobacillus stearothermophilus and Bacillus cereus spores inoculated in different time intervals during simulated cocoa beans fermentation

Abstract

The behavior of G. stearothermophilus and B. cereus during the fermentation of cocoa beans was assessed in this study. Cocoa fermentation trials lasted seven days and were conducted inoculating a cocktail of spores of strains from each species (3 log CFU/g) daily. During the fermentation period, samples were collected for enumeration of counts of G. stearothermophilus and B. cereus indigenous fermenting microorganisms, physicochemical analysis (water activity, pH, carbohydrates, and ethanol, organic acids) and volatile compounds. The findings indicated that the counts of spores of G. stearothermophilus and B. cereus during cocoa fermentation might increase in approximately 2–3 log spores/g. Even though, the inoculation of G. stearothermophilus and B. cereus spores on cocoa beans did not affect (p > 0.05) the counts of the indigenous microorganisms responsible for cocoa fermentation, the consumption of carbohydrates, production of ethanol, organic acids and volatile compounds appeared to be affected by the presence of sporeforming bacteria. These findings indicate that a deep understanding of the role of sporeforming bacteria and their metabolome through cocoa fermentation is critical. Thus, bacterial spores contaminating cocoa beans will likely be found after the fermentation and may further represent food safety or food stability issues.