Researchers probe possibility of developing chocolate flavor through “fine-tuning” cocoa bean processing

27 Aug 2019 --- Researchers and cocoa professionals have been asking if it is possible to manipulate the taste of so-called “noble cocoas” (the varieties Criollo and Trinitario) in different directions to create exciting new flavors. Just as the specialty beers sector has seen a spike in microbreweries, the market for chocolate has also developed with more high-end chocolate manufacturers trying to stand out by fine-tuning the taste and making several different varietals. Therefore, the need to know how to address this during the processing of the noble cocoa is apparent, according to researchers from the Department of Food Science at the University of Copenhagen who conducted this latest study.

Since the vast majority of the world's cocoa production is of the Forastero varietal, much more research has been done on this variety compared to Criollo and Trinitario.

“Criollo cocoa is less bitter than Forastero, but is still more aromatic. You could call it the Pinot Noir of cocoa. But Criollo is a hassle to cultivate and it is difficult to grow in Africa, which is why it is almost exclusively grown in Central America, South America and Madagascar,” says Professor Dennis Sandris Nielsen with Special Responsibilities at the UOC.

“Together with our colleagues from Belgium and Nicaragua, we have, for the first time, examined how different conditions during fermentation affect the composition and activity of microorganisms naturally present on the Criollo beans and how this affects the flavor of the finished fermented beans,” says Professor Nielsen.

It has long been known that the processing of cocoa, which includes the fermentation and drying of the cocoa, is important in relation to the final quality of the cocoa.

“Our research confirms this and we have also learned how to fine-tune the cocoa by fine-tuning the process itself, which means that you can get a higher quality out of your raw materials if you understand these processes,” adds Professor Nielsen.

Flavor is formed in fermentation
A cocoa fruit is the size of a small honey melon and contains around 30 to 40 cocoa beans, which are surrounded by a pulp. If you take a raw cocoa bean and try to make chocolate from it, it does not taste good – further fermentation is required to release the flavor potential, note the researchers. 

The fermentation is done by opening the cocoa fruit, removing the beans and allowing them to ferment – for example, in a box.

The pulp surrounding the beans is inoculated with various microorganisms from the surroundings, equipment, etc. The pulp is very acidic (pH 3-3.5) and has a high sugar content (about 10 percent), and in such an environment only a small number of microorganisms can grow. This is why the fermentation usually goes well, even if it is not inoculated with a starter culture. There is a natural selection of microorganisms that positively affect the taste, the researchers highlight.

Initially, yeast is cultivated, followed by lactic acid bacteria. The yeast forms alcohol, while the lactic acid bacteria eat some of the citric acid that is naturally present, the researchers explain. This means that the pH levels rise, making the environment more favorable for acetic acid bacteria, which converts some of the alcohol that has been formed into vinegar.

The processes generate a lot of heat – reaching approximately 45 to 48 degrees. The alcohol and vinegar penetrate the beans and kill the germs in the cocoa beans so that they can no longer germinate. The cell walls are broken down, meaning that different substances can react with each other, leading to flavor development.

Flavor development continues as the beans dry in the sun, where they are dried until they are microbially stable. Here ends the process for the cocoa farmers, who can now sell the fermented and dried beans. The producers are responsible for roasting the beans, where the substances formed during fermentation and drying react with each other, producing the classic flavor and aroma of cocoa.

In the study, fermentations from different parts of Nicaragua (including highlands and lowlands) as well as fermentations with a variety of oxygen availability were studied.

“By using a combination of High Throughput Sequencing, chromatography and sensory analysis, we can get an understanding of the quality of the cocoa, particularly in relation to the processing. Overall, our findings show that the treatment the cocoa receives after the harvest is at least as important for the quality and flavor as the genetics of the cocoa. Where the cocoa was grown also has some significance. By varying the conditions during fermentation, we can therefore also reasonably predict the final taste, which provides good opportunities for high-end producers, in particular, to develop chocolate with different flavors and scents,” concludes Professor Nielsen.

Edited by Gaynor Selby