Study On The Thermal Denaturation Aggregation Behavior And Gelation Interaction Of Rabbit Myofibrillar Protein And Sarcoplasmic Protein

Rabbit meat is rich in B vitamins,protein,essential amino acids and polyunsaturated fatty acids.And it also has the characteristics of low purine,low cholesterol,low calories and low fat,which can meet the requirements of people for a green and healthy diet.However,the current utilization of rabbit meat products is still mainly in the form of consumption of primary processed products,and the degree of intensive processing is low.In recent years,gel-related products have become more and more popular with consumers because of their low calorie,high water content,and strong satiety.Rabbit meat is rich in protein and has the potential to be a high-quality gel meat product.Myofibrillar protein is the main protein in gel formation,and the gel properties of myofibrillar protein have been extensively studied in the processing of meat products.With the rapid development of the food industry,there is an urgent need for a large number of proteins with excellent functions and nutritional properties as food raw materials or added base materials in actual production applications to meet people’s needs for healthy food.As another important protein in muscle protein(accounting for30-35% of total muscle protein),sarcoplasmic protein has the advantages of wide sources,easy extraction,safety and non-toxicity.However,the research and utilization of sarcoplasmic protein is very low.Although sarcoplasmic protein does not have gel forming ability,it will significantly affect the formation of myofibrillar protein heat-induced gel.In view of this,this thesis takes rabbit muscle myofibril protein and sarcoplasmic protein as the research object.The thermal denaturation aggregation behavior of myofibrillar protein and sarcoplasmic protein in the solution system,the effect of sarcoplasmic protein on gel properties of myofibrillar protein in gel system,and the dynamics of the transition from the two-protein composite solution to the composite protein gel are studied.Then this subject studied the thermal denaturation aggregation behavior of myofibrillar protein and sarcoplasmic protein under different heat treatment conditions,and deeply explored the effect of sarcoplasmic protein on the heat-induced gel of myofibril protein,which is used for the deep processing and utilization of sarcoplasmic protein and the quality control of myofibrillar protein gel products in the meat industry provides a theoretical basis.The main research contents and results are as follows:(1)In the solution system,the thermal denaturation aggregation behavior of rabbit myofibrillar protein and sarcoplasmic protein under different heating temperature(heating at at 35℃,45℃,55℃,65℃,75℃,85℃for 30 min)and heating time(heating at 75℃ for 10 min,20 min,30 min,40 min,50 min)were comparatively studied.The results of the study showed that the degree of denaturation of sarcoplasmic protein during thermal aggregation is greater,and the rate of denaturation is also faster.Natural sarcoplasmic protein has high solubility,and its turbidity,particle size and surface hydrophobicity are much lower than myofibril protein.With the increase of the heat treatment temperature,the solubility of the two proteins continued to decrease,and the turbidity,particle size and surface hydrophobicity continued to increase.Through comparative studies,it is found that when the temperature reaches 55°C,the range of changes in these indicators of sarcoplasmic protein is much greater than that of myofibrillar protein.In the study of different heating time,it was also found that above indexes of sarcoplasmic protein did not change significantly after heating for about 20 min,while myofibrillar protein did not change significantly after heating for 30 min.Both proteins were oxidized significantly during the heating process.The tryptophan fluorescence attenuation of sarcoplasmic protein was significantly greater than that of myofibril protein,and the loss of total sulfhydryl groups was also greater.In addition,microstructure analysis revealed that the two proteins have distinct aggregation modes.During heat treatment,myofibrillar protein particles gradually adhered and aggregated into a larger block structure,while the sarcoplasmic protein sheet structure gradually became scaly and the surface became smooth and dense.(2)In the gel system,the effect of different contents of sarcoplasmic protein(0%,5%,10%,15%,20%,25% and 30%)on the gel properties of myofibrillar protein was studied.The results of the study showed that with the increase of sarcoplasmic protein content,the L* value and a* value of the gel showed a significant decreasing trend,and the b* value showed a significant increasing trend,resulting in a decrease in the whiteness value.When the sarcoplasmic protein content is 20%,the gel strength is the highest and the water retention is the best.When the sarcoplasmic protein content exceeds 20%,the gel strength and water retention decrease.This is consistent with the results of the gel microstructure.Adding 20% of sarcoplasmic protein can make the three-dimensional network structure of the gel more uniform and dense.After increasing the sarcoplasmic protein content,the irregular pores on the gel surface gradually increase.Through dynamic rheological properties and SDS-PAGE electrophoresis analysis,it can be known that sarcoplasmic protein can promote the aggregation and cross-linking of myosin,but when the content of sarcoplasmic protein exceeds 20%,this promotion effect will be weakened.Hydrophobic interactions and disulfide bonds are the main chemical forces in composite protein gels.The addition of20% sarcoplasmic protein can significantly increase the content of hydrophobic interactions and disulfide bonds.At the same time,sarcoplasmic protein can increase the β-sheet content in the gel while reducing the α-helix content,which corresponds to the decrease of the hydrogen bond content in the chemical force.(3)In the process of gel formation,this study mixed different content of sarcoplasmic protein(0%,5%,10%,15%,20%,25% and 30%)with myofibril protein,and studied the physical,chemical and structural properties of the composite protein at different gelation temperatures(35℃,45℃,55℃,65℃,75℃).Research results show that the presence of sarcoplasmic protein can accelerate the denaturation and aggregation of complex proteins at 45-65°C.In the range of 5-20%,with the increase of sarcoplasmic protein content,the trend of changes in solubility,turbidity,surface hydrophobicity and fluorescence intensity of tryptophan becomes more and more obvious.At the same time,sarcoplasmic protein promotes the oxidation of myofibril protein.The higher the sarcoplasmic protein content,the higher the carbonyl content of the composite protein,and moderate oxidation is conducive to the formation of a good gel structure.The results of total sulfhydryl groups and chemical forces showed that the treatment group containing 20% sarcoplasmic protein lost the most sulfhydryl groups during the heating process,and the content of disulfide bonds was also higher.In addition,the thermal denaturation and aggregation of sarcoplasmic protein at 55°C can promote the exposure of hydrophobic groups in the complex protein and the cross-linking of myosin.This leads to a rapid increase in hydrophobic interaction and disulfide bond content at this temperature,which promotes gel formation.But when the temperature reached 75℃,the hydrophobic interaction and disulfide bond content of the25% and 30% treatment groups were lower than that of the 20% treatment group.In conclusion,as a high-quality protein resource,rabbit sarcoplasmic protein can improve the gel properties of myofibrillar protein.Sarcoplasmic protein has a more intense thermal denaturation and aggregation effect under the same heating conditions.Therefore,it can promote the structure expansion and denaturation and aggregation of myofibrillar protein during the gel formation process,thereby improving the gel forming ability of myofibrillar protein.Especially when the amount of sarcoplasmic protein was 20%,the content of hydrophobic interaction and disulfide bond in gel was the highest,and the quality of gel was the best.