Biochemical and functional properties of lactic acid bacteria isolated from Ivorian cocoa fermenting beans

Abstract

Objective: Fermentation is an important step in the post-harvest processing of cocoa beans. The quality of beans and chocolate depends strongly on the type and characteristics of microbial strains involved in the fermentation. This study investigates some functional properties of lactic acid bacteria (LAB), involved in Côte d’Ivoire cocoa fermentation.
Methodology and results: Bacterial growth was monitored during spontaneous heap fermentation using plate count and decimal dilution methods. LAB was present throughout the fermentative process with a load comprised between 6.0 log (UFC/g of bean) at the beginning to 6.60 log (UFC/g of bean) at the end. The maximum load of LAB corresponding to 7.22 log (UFC/g of bean) was reached after 24 h of fermentation in the condition of 42 °C of temperature and pH round 3.55. Among the 150 strains isolated, 99 were lactobacilli and 51 lactococci. Almost all these LAB showed ability to ferment glucose, fructose and sucrose with an important acidification capacity while only 8 strains belonging to lactococci proved to be able to assimilate citrate. Moreover, a weak proportion (7.33 %) of LAB strains isolated was heterofermentative type. These heterofermentative LAB strains were particularly characterized by a great fermentative capacity especially with glucose and sucrose with a gas production up to 5 mL.
Conclusion and application of results: The citrate metabolism and the strong fermentative capacity of certain LAB strains, indicate interesting technological traits potentially useful for their utilization as starters in cocoa fermentation.

Keywords: lactic acid bacteria; fermentative power; cacao fermentation; acidification; citrate metabolism.