Mechanism - guided strategies for the control of the Maillard reaction

当还原糖的羰基与氨基反应时，在食物中以热方式启动美拉德反应，在生物体中自发地启动美拉德反应，从而形成中间产物。这些中间体进一步向下游与其他氨基酸化合物反应，影响食品的主要成分、功能和结构变化，对安全性、颜色、味道、蛋白质功能和消化率产生重大影响。美拉德反应的一个独特特点是它能够从更少和更简单的结构中产生大量产物，从而使分析过程复杂化。在食品科学中，这些反应被称为非酶褐变，在医学上，它被称为蛋白质糖基化。由于它对食品质量和健康的重大影响，需要采取有效的战略来控制它。制定这样的策略需要详细了解反应条件和涉及的机理。由于食物基质的复杂性，许多研究人员采用了“模型系统”的方法，即通过对氨基酸和糖的简单混合物进行反应来了解它们的具体作用。在这项建议中，模型体系(13C或15N标记或未标记)将(A)在110oC的封闭式不锈钢反应器的水溶液中加热1h，然后通过qToF-MS/MS分析，或(B)作为干混合物热解，用于GC/MS挥发性分析，然后将依次通过qToF-MS/MS分析残留物。申请人的长期目标是在不同的环境条件下对不同的糖和氨基酸进行详细的同位素标记实验，以深入了解它们在美拉德反应中的具体作用，以便制定控制策略。我们实验室最近的一项发现表明，Cu2+离子的存在干扰了美拉德反应通过与氨基酸和糖形成二元络合物而产生一系列不同的活性中间体的机制。这项建议的具体目标之一是进一步研究这一观察结果，并了解其他过渡金属(Fe2+、Zn2+、Cd2+、Ca2+、Mg2+)氨基酸二元络合物如何影响美拉德反应的途径。另一方面，从起始氨基酸原位生成羰基捕捉剂是控制美拉德反应速度的一个有吸引力的策略。根据我们的观察，色氨酸能够产生吲哚部分，这些吲哚部分能够清除美拉德反应中的活性羰基化合物，第二个目标是研究其他氨基酸或多肽，如组氨酸、肌氨酸、肌氨酸和精氨酸产生羰基清除部分，如吡咯、咪唑和胍的能力，以控制有害美拉德反应产物的积累。

The Maillard reaction is initiated thermally in food and spontaneously in living organisms when the carbonyl groups of reducing sugars react with amino groups leading to the formation of intermediate products. These intermediates react further downstream with other amino compounds and effect major compositional, functional and structural changes in food with significant impact on safety, color, taste, protein functionality and digestibility. One of the unique features of the Maillard reaction is its ability to generate a large number of products from fewer and simpler structures complicating the analytical process. In Food Science these reactions are referred to as non-enzymatic browning and in medical sciences it is known as protein glycation. Due to its significant impact on food quality and on health, efficient strategies are needed for its control. Developing such strategies requires detailed understanding of the reaction conditions and the mechanisms involved. Due to complexity of the food matrix many investigators have adopted the "model system" approach where simple mixtures of amino acids and sugars are reacted to understand their specific role. In this proposal, model systems (13C or 15N-labelled or unlabeled) will be (a) heated in an aqueous solution in a closed stainless steel reactors at 110oC for 1h and then analyzed by qToF-MS/MS or (b) pyrolyzed as dry mixtures for volatile analysis by GC/MS and the residues in turn will be analyzed by qToF-MS/MS. The long term objective of the applicant is to carry out detailed isotope labeling experiments with different sugars and amino acids under various environmental conditions to generate in-depth mechanistic understanding of their specific roles in the Maillard reaction landscape for the purpose of developing strategies for its control. A recent finding from our laboratories have indicated that the presence of Cu2+ ions interferes with the mechanism of the Maillard reaction generating a different set of reactive intermediates through formation of binary complexes with amino acids and sugars. One of the specific objectives of this proposal is to further investigate this observation and understand how other transition metal (Fe2+, Zn2+, Cd2+, Ca2+, Mg2+) binary complexes of amino acids can influence the pathways of the Maillard reaction. On the other hand, in-situ generation of carbonyl trapping agents from the starting amino acids is an attractive strategy to control the pace of the Maillard reaction. Based on our observation that tryptophan is able to generate indole moieties that are able to scavenge the reactive carbonyl compounds during the Maillard reaction, the second objective is to investigate the ability of other amino acids or peptides such as histidine, carnosine, creatine and arginine to generate carbonyl scavenging moieties such as pyrroles, imidazole and guanidine to control the accumulation of harmful Maillard reaction products.