Fermenting the best chocolate taste

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The production of Belgian national pride products, beer and chocolate, is a natural biotechnological process based on fermentation. Actually, there would be no chocolate flavor in cocoa beans (Theobroma cacao) without the fermentation by Saccharomyces cerevisiae – the same yeast that produces beer. Chocolate flavor is an extremely complex mixture of more than 550 compounds created during the early stages of chocolate production. Do enjoy a piece of Belgian chocolate when reading this article!

What happens during cocoa bean fermentation?
Once extracted from the cocoa pod, the cocoa beans are left for 5-7 days to ferment. The whole process begins with the growth of micro-organisms on the pulp – a sweet mucilage-like coating surrounding the beans. In the case of uncontrolled fermentation, insects are probably responsible for the transfer of yeast and bacteria to the heap of beans, however, nowadays cocoa fermentation is controlled by means of starter cultures. During the first anaerobic phase of fermentation, yeast transforms pulp sugars into ethanol in an exothermic reaction. At this stage, ethanol is oxidized to lactic acid by Lactobacillales (LAB). Pulp breaks down and drains away, allowing for air penetration. In the second (aerobic) phase, Acetobacter (AAB) oxidize ethanol to acetic acid and then to carbon dioxide and water, which further raises the temperature. High temperatures and acetic acid penetrating into the bean causes cell walls to break down, so that previously separated enzymes can react with their substrates. Two protein-degrading enzymes (asparagine protease and a serine protease) successively decompose a cocoa storage protein, vicilin (7S)-class globulin, to peptides and amino acids. Invertase catalyzes the sucrose hydrolysis releasing reducing sugars such as glucose and fructose. These amino acids and sugars are flavor precursors which create chocolate’s defining taste in the roasting process. Moreover, part of polyphenols contained in cocoa beans is oxidized and complexed into large tannin molecules reducing the astringency of the cocoa. Some polyphenols also exudate from the bean, along with 20% of theobromine and caffeine, further reducing the bitter taste. After the fermentation the drying process begins, however, as long as there is enough moisture, flavor forming reactions in the beans continue.

Special kind of yeast for chocolate pioneers
Fermenting yeast has been proven to be essential for the development of chocolate flavor precursors and therefore, the viability of the microbes, their population dynamics, and metabolite kinetics are crucial for the quality of cocoa beans and flavorful chocolate produced thereafter. To control this process, starter cultures (yeast, LAB, AAB) can be added to cocoa beans, improving the fermentation yield and assuring constant production of high-quality fermented dry cocoa beans.

Prof. Kevin Verstrepen’s (VIB / KU Leuven) team isolated hundreds of different yeast strains taking part in cocoa bean fermentation at fermentation research facilities of the Barry Callebaut Group. Based on careful selection and examination of these yeasts, they developed a new strain of cocoa fermentation, which gives desirable features of the end product – the chocolate. This way, the scientist provided the tools not only to make the fermentation process more efficient, but also to control the taste of chocolate.

Better and healthier chocolate
Barry Callebaut Group, with its chocolate research facilities, already has a proven track record in making chocolate healthier and less fattening. The company introduced chocolate where the sweetness was coming entirely from fruits, and an even more diet-friendly sugar free version sweetened with Stevia (in collaboration with a Belgian chocolatier). Recently, they patented a manufacturing process to produce milk chocolate with only 25% fat. Today, Barry Callebaut is the first, in collaboration with the Verstrepen Lab, to craft yeast starter cultures which will enrich and intensify the chocolate flavor.

Chocolate, along with beer and wine, shares the distinction of being a natural fermentation product. Hundreds of years of beer brewing in Belgium taught us that the natural fermentation process could be refined to broaden the taste variety of the final products.  The global improvement in wine quality over the last few years has been significant due to better control of the fermentation process itself. Although beer, wine and chocolate are totally different products, their taste is determined by the particular kind of yeast used in the fermentation process for their production. After creating a wide variety of beers and wines, the time has come for improving the chocolate.