Study On The Properties And Its Application Of The Composite Gel Of Tremella Fuciformis Polysaccharide And Soybean Protein Isolate

The formation of soybean isolate protein（SPI）gels alone is subject to processing conditions and has disadvantages such as poor mechanical properties and low solubility.It is often necessary to add other food ingredients to soy protein isolate in order to achieve a synergistic synergistic compound.As one of the important active ingredients of Tremella fuciformis,Tremella fuciformis polysaccharide（TFP）is of great interest due to its good hydrogel properties.Previous studies have found that the interaction between polysaccharides and proteins can be regulated to obtain ideal food processing ingredients,and multiple processing factors can affect or change the polysaccharide-protein binding system.At present,there are few studies on the improvement of food quality characteristics by combining TFP with macromolecular substances.In this study,TFP and SPI were used as research objects,the gel properties and gel formation mechanism of the TFP-SPI composite system prepared under different conditions were investigated.Meanwhile,the effect of TFP-SPI composite gel on the edible quality of bread was investigated.The main research results are as follows:（1）The TFP-SPI composite gels were prepared under different conditions,and their gel properties were studied.The results showed that the water holding properties,rheological properties,textural properties,and thermal stability of TFP-SPI composite gels were enhanced with the increase of TFP concentration,the above properties were enhanced and then weakened with the increase of p H,and the above properties were better at the heating temperature of 85～95℃and appropriate Na Cl addition（5～10 m M）.LF-NMR results showed that the increase of TFP concentration led to a leftward shift of T₂and a significant increase of P_2band P₂₁,which reduced the mobility of water;at p H 6～8 and Na Cl addition of 5～10 m M had lower T₂and P₂₂,indicating that the mobility of water was weakened at this time;and the increase of heating temperature had little change on T₂,while P₂₂was significantly reduced.MRI showed that the water distribution was more uniform at TFP concentration of 2%,p H=7,and heating temperature of 85～95℃with the addition of 0～10 m M Na Cl.SEM showed that the regular,dense,and ordered three-dimensional honeycomb network structure was present at TFP concentration of 2%,p H=7,and heating temperature of 85℃with the addition of 5～10 m M Na Cl.While acid-base treatment and excess Na Cl addition weakened the gel network structure.（2）The preliminary investigation of the formation mechanism of TFP-SPI composite gels showed that hydrophobic interactions played a major role in the formation of TFP-SPI composite gels,and the SDS-PAGE results indicated that TFP and SPI were covalently cross-linked to form new,larger molecular weight aggregates.As the concentration of TFP increased,a large number of hydrogen bonds were formed in the composite system and interconnected.With the increase of TFP concentration,the absolute value of zeta potential and the average particle size of the composite system increased,and the surface hydrophobicity,fluorescence intensity and free sulfhydryl content of the composite system decreased.The electrostatic interactions,hydrophobic interactions,hydrogen bonding and disulfide bonding in the gel system increased significantly with the increase of TFP concentration.With the increase of p H,the hydrogen bonding content of the composite system was less in acidic conditions.With the increase of p H,the absolute value of zeta potential of the composite system increased,the average particle size of the composite system decreased,the surface hydrophobicity and free sulfhydryl content of the composite system showed an enhancement and then weakening,and the fluorescence intensity of the composite system gradually increased.With the increase of p H,the gel system was mainly dominated by hydrophobic interactions and hydrogen bonding forces,and electrostatic interactions were also involved in inducing gel formation.With the increase of heating temperature,hydrogen bonds were formed between the free amino acid residues in the complex system.The surface hydrophobicity,fluorescence intensity and free sulfhydryl content of the composite system increased with the increase of the absolute value of zeta potential and average particle size,and the denaturation of SPI increased after heating,and a stable gel network structure was formed by hydrophobic interactions,hydrogen bonding and disulfide bonding.The fluorescence intensity and free sulfhydryl content of the composite system showed an overall decreasing trend.When the addition of Na Cl was lower than 10 m M,the electrostatic shielding effect in the system was smaller,and the absolute value of zeta potential,average particle size and surface hydrophobicity of the composite system did not change significantly.When Na Cl was added at 15～20 m M,the electrostatic shielding effect contributed to the decrease of the absolute value of zeta potential and surface hydrophobicity and the increase of the average particle size of the composite system.The moderate amount of Na Cl promoted the generation of disulfide bonds to support the mesh structure of the composite gel,while the electrostatic shielding and hydration effects weakened the electrostatic interactions and hydrogen bonds under the effect of excessive Na Cl,and the composite system was mainly dominated by hydrophobic interactions.（3）The effect of TFP-SPI composite gel on the edible quality of bread was studied,and the results showed that the introduction of TFP-SPI composite gel could increase the specific volume of bread,reduce the baking loss of bread,improve the internal organization of bread,and make the core yellow color of bread obvious.The addition of an appropriate amount of TFP-SPI composite gel improved the total sensory evaluation score of the bread,with the highest overall score in the0.6%addition group.During the bread storage period,the 0.6-1.0%TFP-SPI composite gel added was more effective at maintaining the moisture content of the bread.The hardness and chewiness of bread cores with the addition of TFP-SPI composite gel were significantly lower than those of the non-added group,while the decrease in springiness,cohesiveness,and resilience of bread was slowed down to a certain extent,with the most obvious improvement effect in the 0.6%group.Using the hardness of bread to fit the Avrami equation,after adding TFP-SPI composite gel,the bread aging rate k value decreased,the crystal nucleation mode in each group of bread was spontaneous nucleation,and the n value of TFP-SPI composite gel increased to different degrees.