Influence of acetic acid bacteria on the acidity of the cocoa beans during fermentation.

Abstract

During cocoa fermentation, acetic acid bacteria (AAB) produce acetic acid. The increase and diffusion of this acid in the grain, causes biochemical changes that impact on taste and quality. The acid beans are used in limited quantities in the formulation of products. In Mexico, there is no information about on the behavior of AAB. Therefore, the aim of this study was to isolate and identify the BAA molecularly present during the traditional cocoa fermentation and quantify the production of acid in the grain and the production of each one the BAA. Cocoa samples (1 kg) were collected from industrial boxes every 12 h to complete the fermentation. The AAB were isolated in the media CARR and Acetobacter/ Gluconobacter and Petri dishes were incubated at 37°C for 24 h. The strains were isolated, quantified (CFU) and characterized molecularly (16S rDNA). Acetic acid quantification was determined by Gas Chromatography. The pH was determined with a potentiometer. The traditional fermentation began with high concentrations (5.63 ± 0.26 x 105 CFU/g-1 Dry matter) of BAA showing maximum growth until 48 h, in the same time was observed the greatest decrease in pH and increase acidity in the cocoa beans. Only one strain (ITV61) showed great ability in the production of acetic acid (3.05 ± 0.42%). In the future, strains could be selected and inoculate for to avoid compromising the quality of fermented cocoa beans.