Stadler Richard H, Robert Fabien, Riediker Sonja, Varga Natalia, Davidek Tomas, Devaud Stéphanie, Goldmann Till, Hau Jörg, Blank Imre
Nestlé Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland.
J Agric Food Chem. 2004 Aug 25;52(17):5550-8. doi: 10.1021/jf0495486.
The formation of acrylamide was studied in low-moisture Maillard model systems (180 degrees C, 5 min) based on asparagine, reducing sugars, Maillard intermediates, and sugar degradation products. We show evidence that certain glycoconjugates play a major role in acrylamide formation. The N-glycosyl of asparagine generated about 2.4 mmol/mol acrylamide, compared to 0.1-0.2 mmol/mol obtained with alpha-dicarbonyls and the Amadori compound of asparagine. 3-Hydroxypropanamide, the Strecker alcohol of asparagine, generated only low amounts of acrylamide ( approximately 0.23 mmol/mol), while hydroxyacetone increased the acrylamide yields to more than 4 mmol/mol, indicating that alpha-hydroxy carbonyls are much more efficient than alpha-dicarbonyls in converting asparagine into acrylamide. The experimental results are consistent with the reaction mechanism based on (i) a Strecker type degradation of the Schiff base leading to azomethine ylides, followed by (ii) a beta-elimination reaction of the decarboxylated Amadori compound to afford acrylamide. The beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the nitrogen atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under low moisture conditions decarboxylated model Amadori compounds obtained by synthesis. The corresponding vinylogous compounds were only generated if a beta-proton was available, for example, styrene from the decarboxylated Amadori compound of phenylalanine. Therefore, it is suggested that this thermal pathway may be common to other amino acids, resulting under certain conditions in their respective vinylogous reaction products.
在基于天冬酰胺、还原糖、美拉德中间体和糖降解产物的低水分美拉德模型体系（180℃，5分钟）中研究了丙烯酰胺的形成。我们有证据表明某些糖缀合物在丙烯酰胺形成中起主要作用。天冬酰胺的N-糖基生成约2.4 mmol/mol的丙烯酰胺，相比之下，α-二羰基化合物和天冬酰胺的阿马多里化合物生成0.1 - 0.2 mmol/mol。天冬酰胺的斯特雷克醇3-羟基丙酰胺仅生成少量丙烯酰胺（约0.23 mmol/mol），而羟基丙酮使丙烯酰胺产量增加到超过4 mmol/mol，这表明α-羟基羰基在将天冬酰胺转化为丙烯酰胺方面比α-二羰基更有效。实验结果与基于以下反应机制一致：（i）席夫碱的斯特雷克型降解导致甲亚胺叶立德，随后（ii）脱羧的阿马多里化合物进行β-消除反应生成丙烯酰胺。氮原子两侧的β-位至关重要。甲亚胺叶立德重排为脱羧的阿马多里化合物是关键步骤，如果羰基部分在氮原子的β-位含有羟基则该步骤更有利。通过在低水分条件下使合成得到的脱羧模型阿马多里化合物反应，证明了氨基酸部分的β-消除步骤。仅当有β-质子时才生成相应的插烯化合物，例如，苯丙氨酸的脱羧阿马多里化合物生成苯乙烯。因此，有人提出这种热途径可能是其他氨基酸共有的，在某些条件下会产生它们各自的插烯反应产物。
