Study On The Molecular Force Of Lamb Plasma Proteins-myofibrillar Proteins Composite Gel Formation

As a nutritional, low-cost protein resource, plasma proteins could improve the gel properties ofmeat products significantly. To explain the molecular force of plasma proteins composite gelformation, longissimus dorsi muscle and plasma protein of lamb were used for the experimentalmaterial in the present study. The heat-induced gel properties of lamb myofibrillar proteins andplasma proteins were studied. A model system of plasma proteins-myofibrillar proteins composite gelwas constructed, and the effects of plasma proteins promoting to the texture of the heat-induced gelof lamb myofibrillar proteins were verified. The changes of molecular interactions during the processof gel forming was taken as a key point, and that the molecular forces of hydrophobic interactions,electrostatic interactions, hydrogen bonds and disulfide bonds, which promote the forming ofcomposite gel, were explored. The interaction modes of the myosin and albumin were studied. At last,the applications of plasma proteins on the low salt lamb emulsified sausages were studied. The resultswere as follows:(1) pH had a significantly influence on the heat-induced gel properties of lamb myofibrillarproteins (P <0.05). The highest water-holding capacity and hardness of the lamb myofibrillarproteins were both appeared at pH7.5, with a compact and ordered microstructure (P <0.05).Hydrophobic interactions were the main forces during the lamb myofibrillar proteins heat-inducedgel formation, but disulfide bonds had participated in the formation of gel at low pH. Hydrogenbonds and electrostatic interactions were affected by the pH of the systems.(2) pH had a significantly impact on the heat-induced gel properties of lamb plasma proteins (P<0.05). The highest water-holding capacity and hardness of the lamb plasma protein were bothappeared at pH8.6(P <0.05), and the gel was a typically fine-stranded gel with a compact andordered microstructure. The maximum denaturation temperature of the lamb plasma protein was71.5°C at pH5.0, and80.9°C at pH8.6, respectively. Both of the temperatures were the same to thetemperature of storage modulus transition. The fraction of-helix structure declined, and the randomcoil fraction tended to increase during the heat-induced process. The globins and albumin aggregationwere the main proteins to form the gel through disulfide bonds cross-linking. Some of the51kDaglobins aggregated through dimer firstly and then polymer at pH5.0.(3) Increasing the lamb plasma protein concentration, the gel hardness, water holding capacityof the myofibrillar proteins/plasma proteins composite protein gel would be increased significantly atpH6.2(P <0.05). The highest storage modulus was obtained when10%plasma protein added to thelamb myofibrillar proteins (P <0.05), but the highest hardness of the composite gel was appearedwhen50%plasma protein added (P <0.05). On the contrary, the gel hardness, water-holding capacity,storage modulus was decreased at pH7.5(P <0.05). Composite protein gels with high hardness andwater-holding capacity had a compact and ordered microstructure of three-dimensional network at pH6.2.(4) Hydrophobic interactions and disulfide bonds were the main molecular forces for theformation of the composite gel in the system. Changes of hydrogen bonds and electrostaticinteractions had the main effects on the gel properties of the system with high concentrationmyofibrillar of90%. Electrostatic interactions induced by pH changes was the main factors, whichresulted in the difference gel properties of the composite systems with50%myofribillar and50%plasma.(5) Myosin replaced by50%albumin can be improved the gel properties at pH6.2, butdecreased at pH7.0. Electrostatic interactions induced by pH changes was the main factor, whichresulted in the difference gel properties of the composite systems with50%myosin and50%albumin.The crosslinking reaction between myosin and albumin were involved in all the subfragment of MHCexcept the MLC, since MLC was unable to provide enough sulfydryl to form the disulfide bonds.(6) The lamb sausages containing2%~4%lamb plasma proteins had improved the cooking andtextural properties, and sensory characteristics of the emulsified reduced-sodium lamb sausages. Theaddition of4%lamb plasma proteins achieved a highest score of overall acceptability. The lambplasma proteins could be used in the production of emulsified reduced-sodium lamb sausages,without any detrimental effects on the quality of product.