SCREENING OF POTENTIAL YEAST STARTERS WITH HIGH ETHANOL PRODUCTION FOR A SMALL-SCALE COCOA FERMENTATION IN IVORY COAST

Abstract

Cocoa beans (Theobroma cacao L.) are the raw material for chocolate production. The variability of cocoa beans quality, due to the activity of microbiota involved in cocoa fermentation causes huge economic losses in cocoa-producing countries. To resolve this issue, 743 yeast strains isolated in Ivorian cocoa fermentation were investigated in order to identify potential starters by their ability to resist to physico-chemical stress conditions and to produce enzyme necessary to cocoa fermentation. Thus, out of the 743 investigated yeast strains, 113 showed high fermentative capacity, 19 being able to produce high ethanol contents up to 4,18 % w/v. Out of 19 yeast strains high ethanol producers, two strains Saccharomyces cerevisiae YB14 and Pichia kudriavzevii YP13 were able on one hand to resist to most parameters such as temperature, pH, ethanol, organics acid, and on the other hand they were able to produce specific enzymes like pectinase, β-glucosidase, protease necessary to have a good cocoa fermentation process, and finally to produce acetoin which is desirable for flavor development in the fermentation process. These two strains could therefore be used as starter cultures which may contribute to the control of cocoa fermentation in Ivory Coast.