Effects Of Ca²⁺ On Quality Of Hand-Grabbed Mutton And Structure And Gel Properties Of Myofibrillar Protein

Hand-held lamb is a traditional meat product from the northwest of China,originating from areas where Mongolian,Tibetan,Hui and Uighur minorities live.The process of preparing hand-held lamb is relatively simple and does not require the addition of too many spices and food additives,but the flavour and texture of hand-held lamb differs significantly from region to region using the same cooking method.The process of making hand-held lamb is mainly based on stewing with water,so the difference in water quality is a key factor affecting the quality of hand-held lamb,and the difference in water quality is mainly in the content of Ca²⁺,Mg²⁺,Zn²⁺and other metal ions.In this paper,we propose to study the effect of Ca²⁺concentration on the structure and gel model properties of myofibrillar protein and the edible quality and flavour of hand-held lamb,using Ningxia Yanchi beach lamb as the research object.The main findings of this paper are as follows.1.The hind leg meat of Ningxia beach lamb was used as the raw material to extract myofibrillar protein,and a Ca²⁺-myofibrillar protein simulation system was established.myofibrillar protein was extracted using buffers containing different Ca²⁺concentrations of 0,5,10,30,50 and 100 mg/L.The changes of myofibrillar protein sulfhydryl content,solubility,emulsification and structure were analysed.The results showed that the sulfhydryl content gradually decreased with increasing Ca²⁺concentration（P<0.05）,from 33.719μmol/g at Ca²⁺concentration of 0 mg/L to27.033μmol/g at 100 mg/L,with a consequent increase in myofibrillar protein oxidation.Solubility showed a gradual increase with increasing Ca²⁺concentration（P<0.05）,increasing the solubility of myofibrillar protein.Emulsification activity and emulsion stability both showed an increase followed by a decrease,both reaching a maximum index at a Ca²⁺concentration of 10 mg/L,with the best emulsification,which began to become significantly smaller as the Ca²⁺concentration continued to increase（P<0.05）.As the Ca²⁺concentration increased,the zeta potential values of myogenic fibrils gradually increased and the absolute values gradually decreased（P<0.05）,indicating that the electrostatic repulsion between protein molecules became less;the particle size tended to increase（P<0.05）,indicating that the aggregation of proteins became weaker;the surface hydrophobicity increased（P<0.05）,the overall increase in endogenous tryptophan fluorescence intensity（P<0.05）,the structure of myogenic fibronectin remained stable.2.A Ca²⁺-myofibrillar protein gel model was constructed and the gel properties,microstructure,secondary structure and tertiary structure of the mixed system gels were determined.The results showed that the gel properties such as gel strength,water retention,whiteness and rheological properties of myofibrillar protein gels all showed significant changes.The gel strength gradually increased with increasing Ca²⁺concentration（P<0.05）,the whiteness showed an increasing trend（P<0.05）,the water retention showed a significant increase（P<0.05）when the Ca²⁺concentration increased to 100 mg/L,and the energy storage modulus also showed an overall increase with increasing Ca²⁺concentration（P<0.05）,indicating that the addition of Ca²⁺enhanced most of the indicators in the gel properties and improved the functional structure of the gel.Microstructure maps of the gels taken under scanning electron microscopy showed a gradual dense structure with increasing Ca²⁺concentration.β-folding content of the secondary structure of the gels gradually increased（P<0.05）with increasing Ca²⁺concentration,while the content of random curl did not change significantly（P>0.05）,and the content ofα-helix andβ-turning angle gradually decreased（P<0.05）,indicating that Elevated Ca²⁺concentration promoted protein aggregation and enhanced the interactions between protein molecules and between protein molecules and water.The content of disulfide bonds,hydrophobic interactions and hydrogen bonds increased significantly（P<0.05）and the content of ionic bonds decreased（P<0.05）,indicating that the increase of Ca²⁺concentration could help protein gels maintain the stability of their tertiary structures and enhance the strength,water retention and other indices of the gels by changing the chemical interaction forces.The increase in Ca²⁺concentration helped the protein gels to maintain their tertiary structure and enhance the strength and water retention of the gels by changing the chemical force.3.The effects of different additions of Ca²⁺on the cooking loss rate,water retention,colour,p H,tenderness,fat oxidation,aroma composition,taste substances and protein degradation of hand-caught lamb were investigated using Ningxia beach lamb hind leg meat as raw material.The results showed that with the increase of Ca²⁺addition,there was no significant change in cooking loss rate（P>0.05）,water retention was on the rise（P<0.05）and Ca²⁺helped hand-cooked lamb to retain more moisture.Among the L*,a*and b*values of colour,there was no significant change in L*and b*values（P>0.05）and a*values showed a decreasing trend with increasing Ca²⁺concentration（P<0.05）.The p H value tended to increase with increasing Ca²⁺concentration（P<0.05）;the shear force decreased significantly（P<0.05）,enhancing the tenderness of the hand-held lamb;the TBA value decreased significantly（P<0.05）,inhibiting the fat oxidation of the hand-held lamb.The results of GC-MS analysis of aroma substances showed that the content of dibutyl phthalate and ethyl palmitate in aldehydes and esters decreased significantly（P<0.05）and the content of alcohols increased significantly（P<0.05）with increasing Ca²⁺concentration.Electronic nose tests for volatile flavour substances showed that nitrogen oxides and inorganic sulphides made a significant contribution to the flavour formation of hand-held lamb.the addition of Ca²⁺had an impact on the composition of the aroma components of hand-held lamb.As the concentration of Ca²⁺increased,the content of each flavour-presenting free amino acid and the total amount of free amino acids tended to increase and then decrease（P<0.05）,both at a Ca²⁺concentration of 30-50 mg/L,when the flavour of hand-held lamb was the richest.Electronic tongue analysis of the taste substances showed that the addition of Ca²⁺mainly caused an increase in bitterness and astringency in the taste of hand-held lamb（P<0.05）.The protein degradation index showed a decreasing and then increasing trend with increasing Ca²⁺concentration,with the lowest at a Ca²⁺concentration of 30 mg/L.