pH值和缓冲剂对抗坏血酸-半胱氨酸模式反应形成香味化合物的影响

以固相微萃取-气相色谱-质谱联用技术对抗坏血酸与半胱氨酸的模式反应产物进行鉴定,研究pH值和缓冲剂浓度对模式反应形成香味化合物的影响。依赖于不同的pH值条件,模式反应主要产生呋喃、吡嗪、噻唑、噻吩及含硫脂环化合物,这些化合物种类及产量的变化形成各具特色的肉香风味,呋喃类化合物主要形成于低pH值条件下,而吡嗪类化合物则易于在碱性条件下生成,噻唑类化合物的形成与pH值的依赖性不太显著,但过高的酸度会抑制其生成,中性偏碱的条件对噻吩和含硫脂环化合物的生成有利;Na2HPO4-NaH2PO4缓冲剂对模式反应没有催化作用,它们对模式反应形成香味化合物的影响体现于其维持反应体系pH值稳定的能力,0.20mol/L Na2HPO4-NaH2PO4缓冲剂对维持反应体系pH值的相对稳定是合适的。

Effect of pH and Buffer on Aroma Compound Generation from Model Reaction of Ascorbic Acid with Cysteine

The aroma compounds generated from a model reaction system of ascorbic acid(ASA) and cysteine(Cys) were identified by solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS).The effects of pH and buffer concentration on the formation of aroma compounds were investigated.The major aroma compounds including furans,pyrazines,thiazoles,thiophenes,and alicyclic S compounds were generated in the model reaction system at various pH conditions.The types and amounts of these compounds could result in the formation of distinctive meat-like flavor.Furans were produced mainly under acidic pH conditions.In contrast,pyrazines were easy to generate in an alkaline environment.Thiazoles formation was not affected by pH,but high acidity could inhibit their generation.Neutral or slightly alkaline medium was conducive to the formation of thiophenes and alicyclic S compounds.Na2HPO4-NaH2PO4 buffer did not exhibit catalytic effect on the model reaction;on the other hand,its effect on aroma compound generation from model reaction system was exclusively concentrated on the ability to keep the pH stable.Therefore,0.20 mol/L Na2HPO4-NaH2PO4 buffer is appropriate to maintain a relatively stable pH in the model reaction system.