Lactic Acid Bacteria (LAB) strains are actively involved in the occurrence of aroma compounds during cocoa fermentation

Fermentation is a crucial step in the processing of cocoa into chocolate. The role of microorganisms involved in this process is not well understood. In this study, we investigated the production of aroma compounds by Lactic acid bacteria (LAB) strains during fermentation in pulp simulation medium. LABs were isolated from fermenting cocoa in the region of Nawa (Côte d’Ivoire) and identified at species level using 16S RNA gene sequence phylogeny. The aroma compounds from microbial cultures were extracted using headspace microextration (SPME) method and quantified by Gas Chromatography-Mass Spectroscopy (GC-MS). The identified LAB species were mainly dominated by Lactobacillus plantarum and Leuconostoc mesenteroides with Weissella paramesenteroides, Lactobacillus curieae and Fructobacillu ssp as minor microbiota. The main aroma compounds produced by these LAB strains belonged to the class of alcohol namely methyl butanols (3.190 g/L) and 1,3-butanediols (2.582 g/L). Additionally, Lactobacillus plantarum unlike the other strains, produced ketones such as 2, 3-butadione (0.471 g/L) and 3-hydroxy, 2-butanone (0.604 g/L). These compounds known to be responsible for desirable flavor note were yielded in quantities beyond their odor perception threshold. The maximum production of aroma compounds occurred in the pH range 4-5 and temperature around 35 °C. Taken together, these results indicated the implication of LAB strains in the production of aroma compounds during cocoa natural fermentation.
Keywords: Lactic acid bacteria, aroma compounds, cocoa fermentation, chocolate quality, role .