Preliminary Study On Gelation And Emulsification Properties Of Crocodile Meat Myofibrillar Protein

With the continuous improvement of people’s living standard,the pursuit of healthy diet is increasing.Crocodile meat as a kind of high protein,low fat,low cholesterol quality meat is very consistent with the consumption concept of today’s people.Therefore,it is necessary to develop a kind of crocodile meat products with excelent taste and unique flavor on the basis of crocodile meat.There is a great significance for Chinese crocodile industry to get rid of the production mode which is mainly based on the production and sales of crocodile leather,further improve the utilization rate of crocodile by-products,especially crocodile meat,and increase the added value of crocodile.However,there are some problems in the research and development of low-salt emulsified meat products,such as:decline of gel quality after salt reduction,lack of flavor after partial substitution of sodium salt,etc.However,there are few reports on whetherκ-carrageenan,which is widely used in meat products,can improve the properties of meat products under the condition of substitution of polysaccharide partial metal salt.Therefore,this experiment first studied the gel properties of crocodile myofibrillar protein（MP）from different parts of the meat and selected a part with better gel properties as the research object.Then,the effects of the addition amount of carrageenan on the gelation and emulsification properties of MP under the conditions of partial substitution of NaCl by KCl and CaCl₂ respectively were investigated.The main research contents and results are as follows:1.Gel properties of MPs from different parts of crocodile meatThe objective of this study was to compare the physicochemical and gel properties of myofibrillar from different parts of crocodile.The present study is the first to investigate the effects of different body parts in crocodiles on protein aggregation and gel properties.The study shows that the MP gels from white meat on the tail have higher gel strength and WHC than those from red meat on the torso and legs.The high content of MHC in the tail MPs may be the main reason for its higher gel strength.Furthermore the tail MPs easily aggregated before heating because of higher surface hydrophobicity.After heating,the content of proteinα-helices in the tail decreased more than that in the other two body parts.Heat-induced gels formed distinctive microstructures in different parts,and the denser gel network structure made the tail MP gels have higher gel strength and water holding capacity.According to the rheological properties,there was a higher elasticity protein network structure in the tail.In conclusion,the tail of crocodile（white muscle）has stronger protein gelation properties than other parts（red muscle）,which is conducive to the production of gel products.2.Effect of carrageenan on gel properties of crocodile MPs with KCl/CaCl₂substitute part of NaClBy adding carrageenan（0%,0.1%,0.3%,0.5%）under the condition of partial substitution of NaCl with KCl/CaCl₂,the effects of crocodile tail myofibrillar protein gel properties were studied.In the KCl replacement group,the addition of carrageenan reduced the content of reactive sulfhydryl group,surface hydrophobicity group and total sulfhydryl group,which did not increase the gel strength and WHC of the MP.When the carrageenan was added to 0.3%,the gel strength and water retention were significantly reduced.The non-specific correlations,ionic bonding and hydrogen bonds of MP gels were also weakened by the addition of carrageenan.But rheological properties showed that the addition of carrageenan made the MP solution obtain better viscosity before heating.In the CaCl₂ replacement group,the addition of carrageenan did not decrease the gel strength and WHC of the MP.The addition of carrageenan decreased the content of free sulfhydryl groups,the non-specific correlations and ionic bonding between proteins were also weakened,but the surface hydrophobicity of proteins was not affected significantly.Moreover,the surface hydrophobicity of the 0.3%carrageenan additive group was significantly higher than that of the other groups after heating,which significantly improved the gel strength and WHC of the MP gel.The rheological results are consistent with the gel strength,and it has good elasticity when0.3%carrageenan is added after cooling.3.Effects of carrageenan on emulsifying properties of crocodile MPs with KCl/CaCl₂ substitute part of NaClBy adding carrageenan（0%,0.1%,0.3%,0.5%）under the condition of partial substitution of NaCl with KCl/CaCl₂,the effects of crocodile tail myofibrillar protein emulsifying properties were studied.With the addition of carrageenan,the particle size of emulsion droplets decreased significantly（P<0.05）.The size of the droplets in the KCl replacement environment was slightly larger than that in CaCl₂ replacement environment.The absolute value of potential also increased significantly with the addition of anion polysaccharide carrageenan（P<0.05）,which increased the repulsive force between the droplets and enhanced the stability of the emulsion.In addition,the addition of carrageenan also increased the viscosity of the emulsion.And under the KCl substitution condition,the carrageenan combined with K⁺to form a stronger gel,which made the viscosity of the emulsion higher than that under the CaCl₂ substitution condition.The addition of carrageenan significantly increased EAI and ESI,while TSI decreased,indicating that increasing the addition of carrageenan can significantly increase the stability of emulsion（P<0.05）.When the addition amount of carrageenan reached 0.5%（W/V）,no delamination occurred after standing for 7 days under the K⁺substitution condition.This indicated that carrageenan played a more positive role in improving the stability of emulsion under the K⁺condition.In conclusion,the gelation properties of muscle in different parts of crocodile meat are different.Compared with leg and back muscles,MP in tail had the best gelation properties.With the addition of carrageenan,although the hydrophobicity and sulfhydryl groups of tail MP decreased,the effects of carrageenan addition on the gel properties showed different trends under different salt partial substitution conditions.The emulsifying properties of MP were improved significantly with the addition of carrageenan.Moreover,the emulsifying property of KCl substitution was better than that of CaCl₂ substitution.