Effects Of Soybean Oligosaccharide,Inulin And Peach Gum Polysaccharides On The Gel Properties Of Myofibrillar Protein

The heat-induced gelation properties of myofibrillar protein（MP）determine the hardness,elasticity and slicing quality of meat products to a certain extent.Soybean oligosaccharides,inulin and peach gum polysaccharides are three kinds of functional sugars with different physiological properties and processing characteristics.Studying the effects of these additives on the gel properties of myofibrillar protein is the basis for the application of these additives in meat processing to preparing functional health meat chyme products.Therefore,the effects of soybean oligosaccharides,inulin and peach gum polysaccharides on the properties of MP gel were studied in this dissertation.The causes and mechanisms of the effects of three sugars on the gel properties were discussed from the point of view of MP molecular structure and molecular force.The research results are as follows:The effects of soybean oligosaccharide addition（0%-0.8%）on the water holding capacity,cooking yield,texture characteristics,gel strength coefficient（K’）and frequency dependent index（n’）of MP gel were studied.The microstructure of the gels was observed.The second,tertiary and quaternary structure changes of MP molecules in gelatin under the conditions of soybean oligosaccharide addition were determined.And the correlation between MP gel properties and molecular structure was analyzed.The results showed that the water holding capacity,hardness,K’and storage modulus（G’）of the gel increased significantly,while the n’value decreased significantly with the increase of the addition of soybean oligosaccharide in the range of 0%-0.6%（P<0.05）.There were no significant effects on the cooking yield,cohesion and adhesion of MP gels with soybean oligosaccharide in the range of 0.2%-0.8%（P>0.05）.When the addition of soybean oligosaccharide was 0.6%,the gel network was the most compact and the pore diameter was small.With the addition of soybean oligosaccharide increase,the content ofα-helix structure of MP in the gel decreased,and the content ofβ-sheet of MP in the gel increased,and the surface hydrophobicity and the conjugated bimodal(at 850cm^-1 to 830cm^-1 in Raman spectra)intensity ratio（I850/830）increased.The water holding capacity of MP gel was significantly positively correlated with I850/830,β-sheet and surface hydrophobicity of MP in gels,and the hardness of the gel was significantly positively correlated with the surface hydrophobicity.Based on the study of the effect of inulin addition on the viscosity of MP sol,the effects of inulin addition on the properties and ultrastructure of MP gel were studied.And the formation process of MP gel,the changes of MP molecular force（disulfide bond,hydrophobic interaction,hydrogen bonding and electrostatic interaction）in the gel and their relationship with gel properties were studied to discuss the mechanism of inulin addition affecting the properties of MP gel.The results showed that the addition of inulin significantly increased the viscosity coefficient of MP sols（P<0.05）,but had no significant effect on its flow index n（P>0.05）.The hardness,elasticity and water holding capacity of MP gel with the increase of addition,but the water holding capacity and hardness did not change significantly after inulin addition exceed 1.5%.The cooking yield of gel did not change significantly when the addition of inulin was less than 1.5%,but decreased significantly with inulin addition beyond 1.5%.The gel network was the most compact with 1.0%inulin addition.By measuring the G’,denaturation temperature and denaturation enthalpy of MP during the heating process,it was found that the initial formation and weakening stages of MP gel and the denaturation temperature of myosin,were almost unchanged when the amount of inulin was in the range of 0%to 2.0%.However,the denaturation enthalpy of myosin was significantly reduced when the addition amount exceeded 1.0%.The addition of inulin increased the G’in the gel strengthening region,resulting in further enhancement of MP gel.Under the condition of inulin addition,the total sulfhydryl group content and I850/830 of MP decreased,the surface hydrophobicity increased,and the absolute value of Zeta potential almost unchanged,which indicted that inulin addition could promote the formation of disulfide bond in MP,enhance the hydrogen bonding and hydrophobic interaction between protein molecules.The influence mechanism of inulin addition on the properties of MP gel was as follows:inulin is rich in hydroxyl groups,and can form a helical structure with hydrophobic center in aqueous solution,which induced the exposure of hydrophobic groups in MP,enhanced the hydrophobic interaction and hydrogen bonding between MP molecules,and improved the gel network structure and gel properties.MP gel could achieve the best improvement with 1.0%inulin addition.The peach gum polysaccharides were extracted from raw peach gum.The changes of the property and microstructure of peach gum polysaccharide-MP composite gels,and the molecular structure of MP molecules in composite gels with different polysaccharide content（0%-1.0%）were studied.The results showed that the water holding capacity,hardness and stress relaxation of the mixed gel reached the best state with 0.6%polysaccharide content.The addition of peach gum polysaccharide changed the degree of expansion and gelation strength of myosin molecules in MP during initial formation and weakening stages of gel,and played a significant role in enhancing gel strength.Compared with the pure MP gel of control group,the content ofα-helix structure of MP in mixed gels was decreased,while the content ofβ-sheet structure of MP in mixed gels was increased.S₀-ANS reached the minimum value when polysaccharide content was 0.6%,while I850/830 reached the maximum value.Peach gum polysaccharide improved the properties of MP gel because it stabilized the free water in MP system by swelling in water,and promoted the unfolding ofα-helix and tertiary structure in the process of MP gel formation.However,the peach gum polysaccharide penetrated in the MP gel network with polysaccharide content exceed0.6%which damaged the integrity of MP gel network,resulting in the weakened improvement effect.