Elucidating the role of low molecular weight peptides (< 1 kDa) as Maillard reactant flavour precursors in selected cooked white and red meats using a flavouromics approach

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Meat flavour is formed upon heating via chemical reactions between water and fat-soluble flavour precursors present in raw meat. Although free amino acids, reducing and phosphorylated sugars play a major role via the Maillard reaction, the role of small peptides as Maillard reactants in meat and related products need to be elucidated. The role of low MW peptides as key flavour precursors in various types of meat, their formation, identification and contribution to the generation of key VOCs with a significant impact on cooked meat aroma and flavour will be investigated. Meat extracts (chicken breast, thigh, beef and bison) will be prepared using a developed water extraction method, filtered using a 1 K Da cutoff membrane size and the resulting filtrate will be analyzed using a recently developed high resolution liquid chromatography mass spectrometry technique to identify and quantify all small size compounds present in raw meat. Model systems containing natural concentrations of identified peptides, reducing sugars and amino acids (purchased or synthesized) will be used to investigate the Maillard products generated upon heating. Liquid chromatography (LC) quadruple time of flight (QTOF) Mass Spectrometry (MS) and gas chromatography-MS/MS will be used to identify the intermediary compounds (non and semi-volatiles) and the VOCs generated during heating. Stable isotope amino acids, peptides and sugars (purchased or synthesized) will be used to elucidate the contribution of individual Maillard precursors to generation of key VOCs. Sensory evaluation of model systems and meat samples with added selected peptides will be investigated to further clarify the specific role played by each peptide. Multiple regression statistical analysis and partial least squares (PLS) statistical tests will be performed to elucidate the relationship between peptides, reducing sugars, amino acids and the sensory attributes generated by trained sensory panels. Specific objectives are to: (1) Investigate the formation, identification and quantification of low molecular weight (MW) peptides (< 1 KDa) in meat extracts (chicken breast and thigh, beef, bison and fish) using high resolution mass spectrometry techniques (2) Identify and quantify the volatile organic compounds (VOCs) generated in a model system containing natural concentrations of selected peptides and key reducing and phosphorylated sugars using stable isotope dilution mass spectrometry techniques. (3) Elucidate the individual contribution of selective small peptides to the overall acceptability of cooked meat aroma and flavour in selected meat species using consumer acceptability tests. (4) Determine the sensory attributes generated with added selected peptides to raw meat prior to cooking using a trained sensory panel and (5) Clarify the effect of different cooking methods on data obtained in objectives 1 to 4. Novelty of proposal: Natural proteolytic enzymes are active in muscle post-mortem with a continuous generation of small size peptides over time resulting in a significant increase in meat tenderness and availability of small size peptides as Maillard reactants with a potential significant impact on aroma and flavour. Therefore, this proposal is highly novel in seeking to provide data to elucidate the role played by low MW peptides as Maillard reactants in flavour formation in meat. Significance: Proteolytic enzymes are abundant in many foods generating hundreds of low MW peptides that can act as NH2 donor in the Maillard reaction. A proper understanding of the mechanism by which peptides affect flavour in meat and other complex foods could enable the development of acceptable nutritional formulations containing peptides with selective functional properties.