Effects Of Myofibrillar Protein Aggregation And Conformational Changes On Gel Properties

Myofibrillar protein is the most important protein in muscles,accounting for50%-55% of the total protein content in muscle.It affects the tenderness of muscles,but also the quality of meat products.It is a protein that plays a major role in processing.Changes in the structure and conformation of myofibrillar protein affect the quality of the gel,but most of the current studies have focused on the gel properties.However,it is very little known understanding the conformational changes of proteins and the effect of aggregation on gel formation at the molecular level.Sodium chloride can promote the dissolution of myofibrillar protein,which is the key to the formation of the quality of gel-like meat products.Heating is not only the most common method of use in food processing,but also a necessary condition for denaturing,unfolding of myofibrillar protein and then forming a gel.Transglutaminase can catalyze the cross-linking of proteins within and between molecules,change the structure of proteins,and then change gel properties.Therefore,this paper studies the effects of sodium chloride,temperature,and transglutaminase on the aggregation,conformation and gel properties of myofibrillar protein.The main contents and results of this paper's research are as follows:1.Effects of sodium chloride on aggregation and conformation of pork myofibrillar proteinsHigher sodium chloride concentration contributed to stronger hydrophobic interactions,weaker electrostatic interactions,attractive forces were strengthened and repulsive forces were weakened,the particle size and the total sulfhydryl contentdecreased,more disulfide bonds were induced.Functional properties(G',G',texture and cooking yield)increased with the increase of sodium chloride concentration(p<0.05),while whiteness decreased.The changes in the secondary and tertiary structures of pork myoflbrillar protein in gels generated by sodium chloride content were stronger.Higher ?-sheet content and hydrophobic interactions could be observed,and more proteins were unfolded in gel with 2% and 3% sodium chloride.The results indicated that 2% and 3% sodium chloride could change the protein aggregation degree and protein conformation,improved the water holding capacity and texture properties.2.Effect of temperature on molecular conformation and gel properties of pork myofibrillar proteinsThe denaturation temperatures of myosin and actin measured by DSC were 56°C and 72°C,respectively.When the temperature increased from 56°C to 72°C the particle size of myofibrillar proteins with salt content of 1%,2%,and 3% increased from 3652 nm,3501 nm,and 2889 nm to 4075 nm,3753 nm,and 3209 nm,respectively,the zeta potential increased from-4.04.mV,-8.58 mV,-9.92 m V to-3.66 mV,-4.83 m V,-4.97 mV,respectively,hardness value increased from 61.42,283.89,307.52 g to 137.98,521.03,543.03 g,respectively.At the same salt content,whiteness of myofibrillar protein at 72°C were higher than 56°C,but the cooking yield was reduced.The change of particle size and potential can reflect the degree of protein aggregation.Cooking yield and hardness can reflect the properties of the gel.Therefore,temperature can affect the conformation of myofibrillar protein and thusaffect the gel properties.3.Effect of transglutaminase content on gel properties of pork batterThe additional difference levels of MTGase significantly affected the physical–chemical and protein structure of pork batter.When the different levels of MTGase were added to pork batter,the emulsion stability,cooking yield,hardness,springiness and chewiness increased.When the MTGase content was increased to0.67%,the emulsion stability and cooking yield increased and had little effects from0.67% to 1%.But the hardness,springiness and chewiness of pork batter increased with the increase in the MTGase content.In addition,the pork batter with MTGase had a higher ?-sheet and ?-turn content and lower ?-helices content.Moreover,the frequency changes in OH stretching vibration band showed that the addition of MTGase to pork batter generated stronger hydrogen bonds as water–meat protein interactions,which can be related to the enhancement of water binding.In conclusion,added MTGase from 0.33% to 1% could improve the quality of pork batter and transform protein structure.