On the Role of Amadori Rearrangement Products as Precursors of Aroma-Active Strecker Aldehydes in Cocoa

The unique aroma of cocoa develops during fermentation and roasting. In particular, amino acids are well known to thermally generate the so-called Strecker aldehydes. In addition, 1-amino-1-desoxyketoses, known as Amadori rearrangement products (ARPs), are also suggested as key intermediates in the formation of these odorants. To study their role as precursors of cocoa aroma compounds, selected ARPs as well as the respective amino acids were monitored during different processing steps in order to correlate their amounts with the formation of the corresponding Strecker aldehydes. The amounts of ARPs formed during cocoa fermentation and a comparison with the amounts of Strecker aldehydes generated after roasting showed a good correlation between ARP formation/degradation and Strecker aldehydes formation. Interestingly, the ARPs were already available in unfermented cocoa beans. To unequivocally elucidate the role of ARPs as precursors of the Strecker aldehydes in "competition" with the free amino acids, an isotope enrichment experiment was performed. The obtained data clearly suggested the ARPs as effective precursors of Strecker aldehydes.