Degradation of asparagine to acrylamide by carbonyl-amine reactions initiated by alkadienals

The degradation of asparagine to acrylamide produced by 2,4-decadienals was analysed in detail in an attempt to understand the reactions pathways involved in the formation of acrylamide by oxidised lipids. Thus, the effects of aw, pH, oxygen and lipid content, and time and temperature, were studied in different samples of 2,4-decadienal, 2,4-heptadienal, 2,4-hexadienal, 2-octenal, or ethyl 2,4-decadienoate with asparagine, N-acetylasparagine, asparagine t-butyl ester, glutamine or ammonium chloride. Acrylamide was produced to a higher extent in alkadienal/asparagine mixtures, and the reaction yield increased slightly when the chain length of the oxidised lipid decreased. In addition, the reaction yield was very much reduced when the amino acid was esterified or when an alkenal was employed. Furthermore, acrylamide was not produced when ethyl 2,4-decadienoate, N-acetylasparagine, glutamine or ammonium chloride were employed. These results, together with the detection of 3-aminopropionamide and 2-pentylpyridine in 2,4-decadienal/asparagine mixtures, suggested a potential role of the alkadienal in both the decarboxylation of the amino acid and the later conversion of decarboxylated amino acid into acrylamide. This last conclusion was confirmed by studying the effect of the lipid content in the formation of acrylamide in 2,4-decadienal/3-aminopropionamide mixtures.