pH值对“L-抗坏血酸-L-半胱氨酸-甘氨酸”体系挥发性物质形成的影响

Effects of pH on the Formation of Flavor Compounds in the L-Ascorbic Acid-L-Cysteine-Glycine System

考察了复杂美拉德3组分反应体系“L-抗坏血酸-L-半胱氨酸-甘氨酸(ASA-Cys-Gly)”,在不同pH值(4.5,5.8,7.0,8.0,9.5)溶液中挥发性物质的生成情况。采用顶空固相微萃取-气相色谱-质谱(HS-SPME-GC-MS)联用技术及内标和标准物质对比分析、鉴定各反应体系中挥发性的物质。在各物质自降解及2组分体系反应挥发性物质生成与分布研究的基础上,探讨pH值对L-抗坏血酸-L-半胱氨酸-甘氨酸3组分体系挥发性化合物形成的影响。结果表明,3组分体系生成的挥发性化合物主要为噻吩、噻唑、吡嗪及硫醇等化合物。在不同pH值条件下,3组分反应中各挥发性物质生成的种类及含量有显著差异:噻吩类化合物在酸、碱性条件下均可生成,且种类多,含量高,是复杂美拉德反应体系的优势生成物;而噻唑和吡嗪类化合物主要在中、碱性条件下生成;硫醇类化合物主要在酸性条件下生成。根据各体系中挥发性物质的生成情况,提出不同pH值下各体系挥发性物质可能的形成机制。

The volatile compounds formation from the complex Maillard three-component reaction system, L-ascorbic acid-L-cysteine-glycine(ASA-Cys-Gly), was investigated under different pH(ranging of 4.5, 5.8, 7.0, 8.0, 9.5) conditions. The headspace solid-phase micro extraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS) technology, internal standard and standard material were used to analyze and identify the volatile substances in each reaction system. Meanwhile, the effect of pH on the formation of volatile in the three components complex Maillard system was explored based on research of the volatile generation and distribution in the self-degradation and the two components reaction system. The results showed that the volatile compounds generated from the three components complex Maillard reaction system were various organic substances, such as thiophene, thiazole, pyrazine and mercaptans. There were many kinds of thiophenes with high concentration under acidic and alkaline conditions, which were the dominant product in that reaction system. However, thiazole and pyrazine were major produces under medium alkaline conditions. Mercaptans were mainly generated under acidic conditions. According to the formation and distribution of volatile substances in each system, the possible generation mechanisms of volatile substances under different pH conditions were proposed.