摘要
在亚临界水体系中对几种常见且具有代表性结构的氨基酸自降解行为进行研究,探讨pH对氨基酸自降解生成挥发性物质的影响及氨基酸降解机理.结果表明:由于甘氨酸(Gly)、L-丙氨酸(Ala)、L-精氨酸(Arg)、L-天冬氨酸(Asp)结构简单且热稳定性较好,在亚临界水体系中不会发生降解反应;L-丝氨酸(Ser)和L-苏氨酸(Thr)在亚临界水体系中,可通过脱羧生成中间体氨基乙醛母体,继而生成各种吡嗪类衍生物,其中包括2,3,5-三甲基吡嗪、3,5-二甲基-2-(3-甲基丁基)吡嗪和3,6-二甲基-2-乙基吡嗪等;L-苯丙氨酸(Phe)在亚临界水体系中主要生成苯甲醛、苯乙醛、苯乙酮和7-乙基-1,3,5-环庚三烯等;L-半胱氨酸(Cys)自降解会生成关键中间体巯基乙醛,再通过与各种小分子醛相互作用生成噻吩、噻唑类化合物和多硫化物.根据各体系中挥发性物质生成情况,提出了各氨基酸在亚临界水体系中挥发性物质可能的生成机制.
Abstract
The volatile compounds formation mechanism from the self-degradation of several amino acids was studied in subcritical water(SCW).The effect of pH on the self-degradation of several amino acids to generate volatile substances was discussed.The results showed that glycine(Gly),L-alanine(Ala),L-arginine(Arg)and L-aspartic acid(Asp)could not be degraded in SCW,which might be due to their simple structure and excellent thermal stability.In SCW system,L-serine(Ser)and L-threonine(Thr)could be decarboxylated to generate the intermediate structure of aminoac-etaldehyde,then various pyrazine compounds were generated,which included 2,3,5-trimethyl pyrazine,3,5-dimethyl-2-(3-methylbutyl)pyrazine,and 3,6-dimethyl-2-ethyl pyrazine.Benzaldehyde,phenylacetaldehyde,acetophenone,and 7-ethyl-1,3,5-cycloheptatriene were the major self-degradation products of L-phenylalanine(Phe).The key intermediate mercaptoacetaldehyde was formed from the self-degradation of L-cysteine(Cys),and thiophenes,thiazoles,and polysul-fides were formed by the reaction of mercaptoacetaldehyde with various aldehydes.According to the formation of volatile substances in each system,the possible volatile substances formation mechanism from various amino acids were proposed in SCW.
维普
万方数据