Understanding amino acids and bioactive amines changes during on-farm cocoa fermentation

Abstract

Fermentation is of utmost relevance in cocoa processing. Limited information is available on the impact of fermentation on nitrogenous compounds which are associated with relevant health benefits and aroma quality of chocolate. The objective of this study was to investigate the changes on free amino acids and bioactive amines during cocoa on-farm fermentation. In unfermented cocoa 14 amino acids and five amines were detected, with predominance of glutamic acid, leucine, phenylalanine, serine and spermidine and serotonin, respectively. Fermentation followed its due course, confirmed by total titratable acidity, pH and temperature changes. Amino acids levels varied during fermentation and the final levels were higher compared to the unfermented cocoa. Hydrophobic amino acids were prevalent at the end of fermentation. Total levels of most amines decreased (serotonin disappeared) during fermentation; whereas putrescine remained constant and phenylethylamine increased. Multivariate analysis differentiated three distinct phases for these nitrogenous compounds during fermentation: (i) from 0 to 48 h – high serotonin, tryptamine, and pH; (ii) from 60 to 132 h – high phenylalanine, lysine, leucine, alanine, threonine, phenylethylamine, and acidity; and (iii) 144 h – high glycine, histidine, arginine and phenylethylamine. The possibility of using blends with cocoa from different fermentation times, can lead to fermented cocoa with unique functional and sensory properties.