Mechanism - guided strategies for the control of the Maillard reaction

美拉德反应是在食物中热引发的，在生物体中，当还原糖的羰基与氨基反应导致中间产物的形成时，美拉德反应是自发的。这些中间体与下游的其他氨基化合物发生反应，影响食品的主要成分、功能和结构变化，对食品的安全性、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之处在于，它能够从更少、更简单的结构中生成大量的产物，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促褐变，在医学中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所涉及的机制。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，其中氨基酸和糖的简单混合物进行反应，以了解它们的特定作用。在这个提议中，模型系统（13C或15n标记或未标记）将(a)在封闭的不锈钢反应器中110℃的水溶液中加热1小时，然后用qToF-MS/MS进行分析，或者(b)作为干混合物进行热解，用GC/MS进行挥发性分析，然后用qToF-MS/MS分析残留物。申请人的长期目标是在各种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景观中的具体作用，从而制定控制策略。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的机制，通过与氨基酸和糖形成二元配合物，产生一组不同的反应中间体。本研究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+）氨基酸二元配合物如何影响美拉德反应的途径。另一方面，从起始氨基酸中原位生成羰基捕获剂是控制美拉德反应速度的一种有吸引力的策略。基于色氨酸能够在美拉德反应中产生能够清除活性羰基化合物的吲哚基团的观察，我们的第二个目标是研究其他氨基酸或肽如组氨酸、肌肽、肌酸和精氨酸产生羰基清除基团如吡咯、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.