| Myofibrillar proteins account for about 55～60% of the total muscle protein and play a key role in the gel properties of meat products,which are prone to oxidation during processing and can affect the quality of meat products.Polyphenols are excellent antioxidants and are commonly used to prevent oxidation of meat proteins.However,the addition of higher doses of polyphenols is often required to achieve sufficient antioxidant properties.However,the addition of high doses of polyphenols to meat products can deteriorate the gel properties and adversely affect the quality of meat products.Therefore,it is important to explore ways to inhibit protein-polyphenol interactions to improve the gel properties of meat products.Amino acids are one of the essential nutrients,and their effects as food additives on the functional properties of myofibrillar proteins have been widely studied.However,the effect of amino acids on polyphenol-induced deterioration of myofibrillar proteins gel properties is not clear.Therefore,the aim of this study was to determine the effects of amino acids on the physicochemical,structural and gel properties of MP in the presence of epigallocatechin gallate,and to perform molecular docking analysis to elucidate the regulatory mechanism of amino acids on myofibrillar proteinepigallocatechin gallate interactions.The research results can provide theoretical support and technical support to guide the application of polyphenols in meat product processing.The specific research contents and results are as follows:(1)Study of the regulatory mechanisms of L-lysine(5,10 and 20 m M)on myofibrillar protein-epigallocatechin gallate interactions under different concentrations(10 and 50μmol/g)of epigallocatechin gallate were investigated.The effects of L-lysine on the physicochemical,structural and gelation properties of myofibrillar proteins were also investigated at 10 μmol/g epigallocatechin gallate.The result indicated that 10 μmol/g epigallocatechin gallate had no significant effect on the physicochemical,structural and gel properties of myofibrillar proteins,while 50 μmol/g epigallocatechin gallate induced the excessive structural unfolding and subsequent aggregation of myofibrillar proteins,causing damage to the gel properties of myofibrillar proteins.The effects of L-lysine on the physicochemical,structural and gel properties of myofibrillar proteins were different at different concentrations of epigallocatechin gallate.At 10 μmol/g epigallocatechin gallate,20 m M L-lysine induced the denaturation and aggregation of myofibrillar proteins,and significantly reduced the cooking loss and strength of the gels by 48.18% and 51.43%,respectively.In contrast,at 50 μmol/g epigallocatechin gallate,L-lysine inhibited the excessive hydrogen bonding and hydrophobic interactions between myofibrillar proteins and epigallocatechin gallate,mitigating the damage of epigallocatechin gallate on the structure of myofibrillar proteins,thus inhibiting the aggregation of myofibrillar proteins.As a result,the cooking loss of the gel was reduced(21.18%)and the gel strength was increased(69.23%).Both FTIR analysis and molecular docking indicated that L-lysine could bind to myofibrillar proteins through hydrogen bonding and inhibit the excessive hydrogen bonding between myofibrillar proteins and epigallocatechin gallate.(2)Study of the regulatory mechanism of myofibrillar protein-epigallocatechin gallate interactions under high doses of(50 μmol/g)epigallocatechin gallate conditions with different amino acids(L-arginine,L-histidine and L-proline).Based on the above results,5and 10 m M L-lysine showed similar improvement effects,and 20 m M L-lysine showed significantly better effects,so 10 and 20 m M were chosen for this fraction of amino acids.The results showed that L-arginine,L-histidine and L-proline all inhibited the excessive hydrogen bonding and hydrophobic interactions between epigallocatechin gallate and myofibrillar proteins,and reduced the effects of epigallocatechin gallate on myofibrillar proteins.The effect of 20 m M was better than 10 m M.20 m M L-arginine,L-histidine and L-proline reduced the cooking loss by 35.16%,21.57% and 19.97%,respectively,and increased the gel strength by 47.70%,32.70% and 7.43%,respectively.Notably,the inhibitory effect of these three amino acids on myofibrillar protein-epigallocatechin gallate interactions was L-arginine > L-histidine > L-proline.The structure,number of amino group content and isoelectric point of amino acids influenced the regulatory effect.In summary,L-lysine,L-arginine,L-histidine and L-proline could all regulate myofibrillar protein-epigallocatechin gallate interactions,and the effects of L-lysine and Larginine were better than those of L-histidine and L-proline.The regulatory mechanisms mainly include: amino acids can compete with epigallocatechin gallate for the hydrogen bond binding site of myofibrillar proteins;epigallocatechin gallate may preferentially bind to amino acids via hydrogen bonds;amino acids(excluding L-proline)raise the p H and shift it away from the isoelectric point of myofibrillar proteins,which inhibits the aggregation of myofibrillar proteins. |
