Stadler Richard H, Verzegnassi Ludovica, Varga Natalia, Grigorov Martin, Studer Alfred, Riediker Sonja, Schilter Benoit
Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland.
Chem Res Toxicol. 2003 Oct;16(10):1242-50. doi: 10.1021/tx034088g.
The thermal degradation over temperature and time of selected amino acids (Asp, Gln, and Glu) in the presence of reducing sugars was investigated in low moisture model systems. Copyrolysis of glucose-Asp mixtures led to the release of acrylic acid, attaining >5 mmol/mol Asp at 230 degrees C after 5 min. Spurious amounts of 3-butenamide were detected upon heating Gln together with a carbonyl source. Apparently, intramolecular cyclization is favored to procure 2-pyrrolidinone, reaching levels >3 mmol/mol above 230 degrees C. 2-Pyrrolidinone was also formed in comparable amounts in pyrolyzed sugar-Glu mixtures, indicating that the Maillard reaction may be an important contributor to the formation of 2-pyrrolidinone in certain cooked foods. The chemical route to acrylic acid and 3-butenamide is probably analogous to that described for acrylamide recently. Evidence is also presented that acrylic acid may be an intermediate in the formation of acrylamide, and yields could be augmented by coincubation of fructose-Asp with certain amino acids such as Gln, reaching approximately 5% of the yield obtained by the Asn route. A computational study to determine the reactivity of the vinylogous products indicated a reduced ability of 3-butenamide as compared to acrylamide to form stable intermediates by Michael nucleophilic addition. Acrylamide and acrylic acid exhibited a similar theoretical reactivity potential toward nucleophiles. No information is as yet available on the occurrence of acrylic acid in cooked foods. Extensive toxicological evaluation indicates that acrylic acid is of no concern at the amounts to be expected in foods.
在低水分模型体系中，研究了在还原糖存在下选定氨基酸（天冬氨酸、谷氨酰胺和谷氨酸）随温度和时间的热降解情况。葡萄糖 - 天冬氨酸混合物的共热解导致丙烯酸的释放，在230℃下5分钟后，每摩尔天冬氨酸释放量>5 mmol。将谷氨酰胺与羰基源一起加热时，检测到少量的3 - 丁烯酰胺。显然，分子内环化有利于生成2 - 吡咯烷酮，在230℃以上其含量>3 mmol/mol。在热解的糖 - 谷氨酸混合物中也以相当的量形成了2 - 吡咯烷酮，这表明美拉德反应可能是某些熟食中2 - 吡咯烷酮形成的重要因素。丙烯酸和3 - 丁烯酰胺的化学形成途径可能与最近描述的丙烯酰胺的形成途径类似。也有证据表明丙烯酸可能是丙烯酰胺形成过程中的中间体，果糖 - 天冬氨酸与某些氨基酸（如谷氨酰胺）共同孵育可提高其产量，达到天冬酰胺途径产量的约5%。一项确定乙烯基类似物反应活性的计算研究表明，与丙烯酰胺相比，3 - 丁烯酰胺通过迈克尔亲核加成形成稳定中间体的能力降低。丙烯酰胺和丙烯酸对亲核试剂表现出相似的理论反应活性潜力。目前尚无关于熟食中丙烯酸存在情况的信息。广泛的毒理学评估表明，食品中预期的丙烯酸含量无需担忧。
