Protein Profile Of Rabbit Meat And Physicochemical Properties Of Rabbit Glycated Myofibrillar Protein With High Solubility In Low Ionic Strength Medium

Rabbit meat is an excellent nutritional source of food and is a high quality source of protein for human.However,there are few basic researches on rabbit meat protein and the high value-added utilization rate of rabbit meat protein is relatively low,which result in the low profit of rabbit industry.With the development of national economy and the improvement of people's living standards,the concept of people diet become much healthy.Therefore,low salt foods have been getting huge market demand.As the most abundant protein in rabbit meat,myofibrillar protein plays a important role in the quality of rabbit meat products.As the basis of functional properties of protein,solubility is very important for meat product quality;but the solubility of myofibrillar protein in low ionic strength medium is very low,which greatly limits its wide application in low salt foods.There are many ways to increase the myofibrillar protein solubility in low ionic strength medium,among which protein glycation requires safe and mild conditions and no toxic chemical reagents and has attracted the attention of researchers over recent years.However,the physicochemical properties and structural properties of the protein will also change during the process of glycation.At the same time,the changes in external environment will also lead to the related variation in the physicochemical properties of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium.Therefore,the present study aimed at investigating the effect of breed and age on the protein profile of rabbit meat.This research may lay the foundation for wide utilisation of rabbit meat protein.At the same time,a better production process of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium was obtained through the ultrasonic assisted dry heated glycation,and its structure and physicochemical properties were discussed in depth.Furthermore,the effect of ionic strength on the physicochemical properties of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium was studied.Finally,the difference of physicochemical properties between glycated myofibrillar protein and native myofibrillar protein was studied under low ionic strength condition,and the correlation between the solubility of glycated myofibrillar protein and other physicochemical properties was explored under different ionic strength,which will lay a foundation for its further application in low salt rabbit meat food.The main results are as follows:(1)The composition of amino acids in the muscles of Ira rabbits with different genders(male and female)and ages(35,70,and 105 days)were studied.Meanwhile,the proportion of sarcoplasmic protein,myofibrillar protein,and stromal protein in the muscles of Ira rabbits was analyzed.The protein profile of rabbit meat was studied using shotgun proteomics,and the solubility of rabbit myofibrillar protein under different ionic strength was studied.The results showed that there were higher protein and essential amino acids in rabbit meat when compared to other livestock meats,among which the content of lysine was very high.The contents of some amino acids,such as leucine and threonine,were significantly affected by age.The average proportion of sarcoplasmic protein,myofibrillar protein,and stromal protein in total protein in rabbit meat was 32.55%,57.16%,and10.29%,respectively.Additionally,the amino acid composition of sarcoplasmic protein,myofibrillar protein,and stromal protein in rabbit meat was different.The content of essential amino acid in myofibrillar protein was the highest,reaching 41.67 g/100 g protein,and the content of Pro,Ala,and Gly in stromal protein was the highest among these three kinds of proteins.Age had a significant effect on the content of stromal protein in rabbit meat.At the same time,A total of 820 proteins were identified from the samples using shotgun proteomics.These proteins were mainly involved in energy metabolism,material transport,and biochemical reactions,and the highest number of proteins was observed in meat of 35-day-old rabbit,and gender had no significant effect on the quantity of protein.In addition,the solubility of rabbit myofibrillar protein in 0.1 mol/L Na Cl was very low,and the ionic strength can significantly affect its solubility,which need further research on improving its solubility in low ionic strength medium.(2)The effects of glucose addition and ultrasonic treatment(ultrasonic power,ultrasonic time,and ultrasonic frequency)on the solubility of rabbit glycated myofibrillar protein in low ionic strength medium were studied.Additionally,the effects of temperature,time,and relative humidity on the solubility of rabbit glycated myofibrillar protein in low ionic strength medium analyzed.Furthermore,the production parameters of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium were optimized by central composite design on the basis of single factor experiment,and the quadratic regression equation was established.The results showed that the solubility of glycated myofibrillar protein in 0.1 mol/L Na Cl was significantly affected by the amount of glucose addation and the ultrasonic treatment,and the glucose addition was 0.5 mol/L,and the ultrasonic conditions were as follows: ultrasonic frequency 25 k Hz,ultrasonic power 500 W,and ultrasonic time 15 min.Temperature,time,and relative humidity all can affect the process of protein glycation during glycation.Finally,the optimized production process of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium were obtained: reaction temperature was 52.40 °C,reaction time was 23.10 h,and the relative humidity was 39.10%.The final solubility of glycated myofibrillar protein in low ionic strength medium was(75.07 ± 1.86)%.The relative errors between measured values and the predicted values were less than 5%,which showed that the regression model was effective,and the parameters of reaction conditions of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium optimized by central composite design were accurate and reliable.These results are important for the further utilization of rabbit myofibrillar protein and the low salt rabbit meat products.(3)The structure of rabbit glycated myofibrillar protein with different solubility in low ionic strength medium was studied.The contents of fructosamine and lysine,SDS-PAGE,Fourier transform infrared spectroscopy,Raman spectroscopy,intrinsic fluorescence,UV absorption spectra,surface hydrophobicity,and hydrogen bond content were analyzed.The results showed that the structure of rabbit glycated myofibrillar protein with different solubility in low ionic strength medium was quite different.Glycated myofibrillar protein with higher solubility in low ionic strength medium had higher fructosamine content and lower lysine content.In addition,glycated myofibrillar protein with higher solubility in low ionic strength medium had higher glucose residue binding,lower electrophoretic mobility,lower ?-helix content,and higher random coil content;however,there were no significant difference in the ratio of ?-sheet and ?-turn of rabbit glycated myofibrillar protein with different solubility.At the same time,the advance structure of rabbit glycated myofibrillar protein was different when the solubility in low ionic strength medium was different.With the increase of solubility,the intrinsic fluorescence intensity of glycated myofibrillar protein decreased and the red shit of ?max increased gradually.The absorption peak of UV spectrum increased,and the red shift was found.Moreover,the surface hydrophobicity of glycated myofibrillar protein increased first and then decreased with the increase of solubility,and the hydrogen bond content increased with the increase of solubility.In conclusion,the structure of rabbit glycated myofibrillar protein will be different with the change of solubility in low ionic strength medium,which was mainly caused by glycation.(4)To analyze the physicochemical properties of rabbit glycated myofibrillar protein with high solubility in low ionic strength and enrich the utilization of myofibrillar protein,the glycated myofibrillar protein with different solubility in low ionic strength medium was prepared.The solubility in 0.1 mol/L Na Cl was(15.10 ± 0.76)%,(35.03 ± 1.01)%,(55.06 ±1.25)%,and(75.07 ± 1.86)%,respectively.SDS-PAGE,foaming properties,emulsifying properties,gel properties,rheological properties,and thermal stability under different p H conditions(p H 6.0/7.5)were determined.The results indicated that the electrophoretic mobility of glycated myofibrillar protein with different solubility in low ionic strength medium were different.The higher the solubility,the lower the electrophoretic mobility.The glycated myofibrillar protein with higher solubility in low ionic strength medium had higher foaming property and foaming stability,and better emulsifying property and emulsifying stability than those with low silubility did.When the solubility of glycated myofibrillar protein was(35.03 ± 1.01)%,the gel strength and water holding capacity were the highest,and the gel microstructure was more compact and meticulous.p H had no significant effect on the gel strength.Furthermore,the storage modulus(G')of glycated myofibrillar protein increased as the solubility increased within the range of(15.10 ±0.76)% to(35.03 ± 1.01)%,but decreased after the solubility reached(55.06 ± 1.25)%.Results also suggested that the glycation process can improve the thermal stability of myofibrillar protein;glycated myofibrillar protein with(75.07±1.86)% solubility had the highest denaturation temperature.In conclusion,the physicochemical properties of rabbit glycated myofibrillar protein were affected by changes in solubility in low ionic strength medium;rabbit glycated myofibrillar protein with high solubility was more resistant to p H changes than native myofibrillar protein.(5)The changes of physicochemical properties of rabbit glycated myofibrillar protein with high solubility in low ionic strength meidum and rabbit native myofibrillar protein under different ionic strength medium(0.1,0.2,0.3,0.4,and 0.5 mol/L Na Cl),such as solubility,foaming properties,emulsification properties,surface hydrophobicity,active sulfhydryl content,and hydrogen bond content were analyzed.The results showed that the ionic strength had a significant effect on the physicochemical properties of native myofibrillar protein and rabbit glycated myofibrillar protein with high solubility in low ionic strength.The solubility of glycated myofibrillar protein in 0.1 mol/L Na Cl was as high as that of native myofibrillar protein in 0.4 mol/L Na Cl.The ionic strength can significantly improve the foaming properties and emulsifying properties of glycated myofibrillar protein with high solubility in low ionic strength medium.Moreover,the foaming and emulsifying capacities of glycated myofibrillar protein in 0.1 mol/L Na Cl was higher than that of native myofibrillar protein in 0.5 mol/L Na Cl.Meanwhile,the surface hydrophobicity and hydrogen bond content of glycated myofibrillar protein and native myofibrillar protein increased with the increase of ionic strength,but the stability of rabbit glycated myofibrillar protein with high solubility in low ionic strength was more resistant to ionic strength changes than native myofibrillar protein.Additionlly,the solubility of native myofibrillar protein was significantly positively correlated with foaming ability,emulsifying properties,emulsifying stability,and surface hydrophobicity under different ionic strength,and was positively correlated with foaming stability,active sulfhydryl group content,and hydrogen bond content.However,the solubility of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium was significantly positively correlated with foaming ability,active sulfhydryl group content,and surface hydrophobicity,and was positively correlated with foaming stability and emulsion stability,but had no significant correlation with emulsion ability and hydrogen bond content under different ionic strength.In conclusion,the method of glycation can be used to improve the solubility of rabbit myofibrillar protein in low ionic strength medium.Compared with the native myofibrillar protein,the physicochemical properties of rabbit glycated myofibrillar protein with high solubility in low ionic strength medium had better stability to the external environment.Meanwhile,rabbit glycated myofibrillar protein with high solubility in low ionic strength medium had better functional properties under the condition of low ionic strength,which has a great potential of application to promote the innovation of low salt rabbit meat products,expand the new rabbit meat consumption market,and improve the profits of rabbit industry.