Amino-Acid-Derived Toxins and Pyrazines in Chocolates and Cocoa-Free Chocolate Surrogates

This study investigated the influence of cocoa-bean amino acid profile on the formation of α,β-unsaturated carbonyls. Some of these heat-derived compounds generated primarily during roasting (often through Strecker degradation and aldol condensation) are of toxicological concern (e.g., the aneugenic 2-phenylcrotonaldehyde and the genotoxic furan-2(5H)-one). Here, their levels were compared by SAFE-GC/MS in cocoa of different origins, before and after roasting. Free amino acid profiles were determined by HPLC-MS/MS. All the investigated roasted beans showed similar total free amino acid contents (10.5–15.0 g·kg−1) and profiles, while α,β-unsaturated aldehyde levels differed markedly between samples, and reached >200 µg·kg−1 after roasting, indicating that amino acid availability alone does not govern their formation. Analysis of a commercial cocoa-free chocolate surrogate, however, revealed much lower amounts of both free amino acids (total 1.6 g·kg−1) and amino-acid-derived α,β-unsaturated aldehydes (total 11 µg·kg−1) than in chocolate, together with only traces of pyrazines (total 72 µg·kg−1). In contrast, furan-2(5H)-one was found at similar levels in chocolate and the cocoa-free product (56–79 µg·kg−1), confirming a completely different pathway where amino acids are not key reagents in its synthesis.