Mechanism - guided strategies for the control of the Maillard reaction

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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.