Abstract
Yeast starters for cocoa fermentation are usually tested according to their enzymatic activities in terms of mucilage degradation and flavor improvement, disregarding their influence on the production or elimination of toxic compounds as biogenic amines (BAs), important for human health. In this work, we tested 145 strains belonging to 12 different yeast species and isolated from the Colombian fermented cocoa beans (CB) for their capability of producing BAs in vitro. Sixty-five strains were able to decarboxylate at least one of the amino acids tested. Pichia kudriavzevii ECA33 (Pk) and Saccharomyces cerevisiae 4 (Sc) were selected to evaluate their potential to modulate BAs, organic acids, and volatile organic compounds (VOCs) accumulation during a simulated cocoa fermentation. The growth of Sc or Pk in the presence of CB caused a significant reduction (p < 0.05) of 2-phenylethylamine (84% and 37%) and cadaverine (58% and 51%), and a significant increase of tryptamine and putrescine with a strong influence of temperature in BA formation and degradation. In addition, our findings pointed out that Pk induced a major production of fatty acid- and amino acid-derived VOCs, while Sc induced more VOCs derived from fatty acids metabolism. Our results suggest the importance of considering BA production in the choice of yeast starters for cocoa fermentation.
Highlights
Cocoa beans fermentation is driven by a complex of microorganisms that accomplish their activity in a well-defined chronological succession of yeasts, lactic acid bacteria (LAB), acetic acid bacteria (AAB), Bacillus, and filamentous fungi
For the first time, we report a high intraspecific variability in amino acid decarboxylase activity of yeasts isolated from Colombian cocoa beans
In particular, S. cerevisiae 4 and P kudriavzevii ECA33, showed interesting technological properties, revealed by their ability to induce favorable changes in the cocoa bulk and on biogenic amines (BAs) degradation and volatile organic compounds (VOCs) production, as a result of an energy-efficient growth and of the aptitude to react to a changing environment
Summary
Cocoa beans fermentation is driven by a complex of microorganisms that accomplish their activity in a well-defined chronological succession of yeasts, lactic acid bacteria (LAB), acetic acid bacteria (AAB), Bacillus, and filamentous fungi These microbial activities are important to the degradation of the mucilage and for the production of molecules that are precursors of the distinctive aroma, flavor and color, which are formed during drying and roasting [1]. The main impact of yeasts to the cocoa beans fermentation process is due to the alcoholic fermentation of the pulp sugars and pectin degradation that facilitates bean aeration, favoring bacterial development, and starting the second phase of fermentation [2] They contribute to the development of the aroma precursors important to the formation of sensory profiling for cocoa beans [3] by different enzyme activities [4]. Another less studied concern regarding cocoa fermentation is the production of biogenic amines (BAs) during the process, which has harmful effects on cocoa quality and human health [6]
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