Forcing fermentation: Profiling proteins, peptides and polyphenols in lab-scale cocoa bean fermentation.

Area of Science:

• Food Science and Technology
• Microbiology
• Biochemistry

Background:

• Cocoa bean fermentation is a critical step influencing final flavor.
• Understanding microbial dynamics and metabolic changes is key to optimizing cocoa quality.
• Lab-scale models are essential for controlled study of complex fermentation processes.

Purpose of the Study:

• To replicate large-scale spontaneous cocoa fermentation dynamics in a controlled lab setting.
• To investigate the impact of microbial growth, particularly acetic acid bacteria (AAB), on cocoa bean metabolomics.
• To identify key metabolites, including peptides, responsible for cocoa-specific flavor and aroma.

Main Methods:

• Lab-scale fermentation of 300-g cocoa bean heaps under controlled conditions.
• Monitoring growth profiles of yeast and acetic acid bacteria (AAB) with native and starter cultures.
• Analysis of metabolic changes, including pH, acetic acid production, polyphenol preservation, and peptide generation.

Main Results:

• Yeast and AAB growth profiles closely matched literature data for spontaneous fermentations.
• Elevated acetic acid production by AAB increased liquor acidity and bitterness via polyphenol preservation.
• Significant pH drop induced by AAB enhanced proteolytic activity, generating peptides similar to those linked to cocoa flavor.

Conclusions:

• Acetic acid bacteria play a significant role in cocoa fermentation, influencing flavor through acidity, bitterness, and proteolysis.
• The study identified specific peptide repertoires generated by cocoa storage protein breakdown.
• A potential peptide responsible for cocoa-specific aroma was highlighted, warranting further investigation.