Interaction Between Tremella Fuciformis Polysaccharide And Soybean Protein Isolate And Its Effect On The Gel Properties Of Lactobacillus Plantarum-induced Protein

Tremella is a large edible fungus with functional activity that have alarge production and sales in my country.The current processing methods are mainly dry products and solid beverages.The lack of intensive processing and the low added value of the products greatly limit the development of the tremella industry.Tremella fuciformis polysaccharide,the main component of Tremella,has anti-tumor,antioxidant,hypoglycemic,hypolipidemic,probiotic and other functions,and has the characteristics of low concentration,high viscosity,and high water holding capacity,and has the potential of functional colloid ingredients.However,there are few studies on using the interaction between Tremella fuciformis polysaccharides and other biological macromolecules to change the quality of food.This subject takes Tremella fuciformis polysaccharide as the object to study the interaction between Tremella fuciformis polysaccharide and soybean protein isolate in aqueous solution and the influence on the protein gel properties induced by Lactobacillus plantarum,in order to develop Tremella fuciformis polysaccharide as a functional food ingredient in plants.The application in protein system provides theoretical basis.The main conclusions are as follows:（1）Tremella fuciformis polysaccharide and soy protein isolate form complexes through electrostatic interaction,hydrophobic interaction and hydrogen bond.p H value,their ratio and salt ion concentration have a great influence on the formation of composite condensate.When SPI:TFP>1,the critical p H value associated with complex formation(p H_cand p H_φ1)shifted to higher p H.While SPI:TFP<1,p H_cand p H_φ1shifted to lower values.With the increased of TFP ratio,the maximum absorption peak of turbidity gradually decreased(p H_optgradually decreased).When SPI:TFP=1:1,the electrostatic interaction between the two is the strongest at p H 3.0.At this time,the viscosity of the system is the largest,which is 1.30 Pa.s,forming the most aggregates and the largest particle size.When the salt ion concentration is less than 20 mmol/L,the formation of SPI/TFP aggregates can be promoted,and when the salt ion concentration is greater than or equal to 20 mmol/L,the formation of aggregates can be inhibited.When the Na Cl concentration is 20 mmol/L and SPI:TFP=2:1,the storage modulus and loss modulus of the system reach the maximum values of 9.24 Pa and 3.40 Pa.（2）The effects of Tremella fuciformis polysaccharides on the protein structure and molecular forces during the formation of SPI gels induced by Lactobacillus plantarum were studied.Lactobacillus plantarum fermentation can change the conformation of SPI and enhance the order of the system.TFP promotes the conversion ofβ-turns and random coils toα-helices andβ-sheets in the secondary structure of SPI.The network structure of SPI gels is mainly maintained by non-covalent bonds such as ionic bonds,hydrogen bonds,hydrophobic interactions and disulfide bonds.The addition of TFP weakened the ionic and hydrogen bonding forces in the gel network structure,and enhanced the hydrophobic interactions,disulfide bonds and non-disulfide covalent bonds.With the prolongation of fermentation time,theα′andαsubunits of the 7S component in SPI dissociated and the content decreased,while the content ofβsubunit increased accordingly,TFP can promote the polymerization ofβsubunits.（3）The effects of Tremella fuciformis polysaccharide on the texture,water distribution,and microstructure during the formation of SPI gels induced by Lactobacillus plantarum were studied.2-4 h was the most significant period of changes in gel texture,moisture,Lactobacillus plantarum quantity and microstructure.The addition of TFP significantly reduced the hardness and elasticity of the gel,and significantly increased the cohesion.TFP can promote the growth of Lactobacillus plantarum within 0-2 h of fermentation,and inhibit the growth of Lactobacillus plantarum within 4-6 h of fermentation.With the prolongation of fermentation time,the lamellar structure of SPI is gradually broken,and formed aggregates with honeycomb structure after 6 h of fermentation.TFP reduces the smoothness of the SPI surface and forms aggregates with larger pores and weaker rheology.TFP can improve the scavenging ability of the gel to DPPH free radicals,but has little effect on the scavenging ability of·OH.