Model Studies on the Oxygen-Induced Formation of Benzaldehyde from Phenylacetaldehyde Using Pyrolysis GC-MS and FTIR
Model Studies on the Oxygen-Induced Formation of Benzaldehyde from Phenylacetaldehyde Using Pyrolysis GC-MS and FTIR
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DOI：
10.1021/jf8022468
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发表时间：
2008-11-26
影响因子：
6.1
通讯作者：
Yaylayan, Varoujan A.
中科院分区：
文献类型：
--
作者：
Chu, Fong Lam;Yaylayan, Varoujan A.
苯甲醛，苦杏仁的一种强有力的香气化学物质，也可以由苯丙氨酸热形成，并可能有助于形成异味。为了确定美拉德反应中参与其生成的前体，使用氧化和非氧化Py-GC-MS研究了含有苯丙氨酸、苯丙酮酸、苯乙胺或苯乙醛的各种模型系统。数据分析表明，苯乙醛（苯丙氨酸的streker醛）是最有效的前体，空气和水都显著提高了苯乙醛生成苯甲醛的速度。在非氧化条件下，苯丙酮酸是最有效的前体。另一方面，苯乙胺需要羰基化合物的存在才能在氧化条件下生成苯甲醛。在此基础上，提出了烯醛化苯乙醛碳碳双键的氧化裂解可能是苯甲醛形成的主要机制，并通过FTIR分光光度计在存在和不存在1,1'-偶氮（环己烷腈）的情况下监测加热后的苯乙醛在ATR晶体上的苯甲醛带的演变提供了支持证据。在自由基引发剂的存在下，苯乙醛以1684 cm（-1）为中心的烯醇带形成并随时间增加，加热18 min后，以1697 cm（-1）为中心的苯乙醛带形成并增加，以苯乙醛的烯醇带为代价，表明前体产物的关系。
Benzaldehyde, a potent aroma chemical of bitter almond, can also be formed thermally from phenylalanine and may contribute to the formation of off-aroma. To identify the precursors involved in its generation during Maillard reaction, various model systems containing phenylalanine, phenylpyruvic acid, phenethylamine, or phenylacetaldehyde were studied in the presence and absence of moisture using oxidative and nonoxidative Py-GC-MS. Analysis of the data indicated that phenylacetaldehyde, the Strecker aldehyde of phenylalanine, is the most effective precursor and that both air and water significantly enhanced the rate of benzaldehyde formation from phenylacetaldehyde. Phenylpyruvic acid was the most efficient precursor under nonoxidative conditions. Phenethylamine, on the other hand, needed the presence of a carbonyl compound to generate benzaldehyde only under oxidative conditions. On the basis of the results obtained, a free radical initiated oxidative cleavage of the carbon-carbon double bond of the enolized phenylacetaldehyde was proposed as a possible major mechanism for benzaldehyde formation, and supporting evidence was provided through monitoring of the evolution of the benzaldehyde band from heated phenylacetaldehyde in the presence and absence of 1,1'-azobis(cyclohexanecarbonitrile) on the ATR crystal of an FTIR spectrophotometer. In the presence of the free radical initiator, the enol band of the phenylacetaldehyde centered at 1684 cm(-1) formed and increased over time, and after 18 min of heating time the benzaldehyde band centered at 1697 cm(-1) formed-and increased at the expense of the enol band of phenylacetaldehyde, indicating a precursor product relationship.