Construction Of Mixed Gel System Based On Soybean Protein Isolate And Its Application In Plant-based Meat

Compared with traditional meat products,the production of plant-based meat products not only consumes less resources,but also has less environmental pollution,which is conducive to the sustainable development of global ecology.Soybean protein isolate（SPI）is a commonly used protein raw material in plant-based meat products.However,the hardness of SPI gel is insufficient.How to effectively improve the gel properties of SPI gel has become one of the key issues in the development of plant-based meat products.The development of SPI based mixed gels with high hardness may provide a solution,as mixed gels usually exhibit excellent gel properties.This study constructed a multi-component mixed gel system of protein and polysaccharide based on SPI to simulate the tissue structure of lean meat,and comprehensively explored the existing form of soybean dietary fiber（DF）,potato protein（PP）,egg white protein（EW）,and konjac glucomannan（KG）in heat-induced SPI gel and their effects on the gel properties of the mixed gel.The formation mechanism of multi-component mixed gels was revealed through the analysis of microstructure,intermolecular interaction,and the degree of crosslinking of dispersed aggregates.Finally,the plant-based lean meat system was mixed with the animal fat tissue that simulated by starch-based emulsion gel,and the plant-based marbled meat products were prepared by one-step heating method.This study can provide theoretical guidance for effectively improving the gel properties of plant-based meat products,and provide new ideas for product development.The main research contents and results are as follows:（1）Firstly,the gel properties of SPI and DF mixed gels in 0 mol/L Na Cl and 0.1mol/L Na Cl systems were investigated to determine the optimal DF/SPI ratio that could improve the hardness of soybean protein isolate-soybean dietary fiber（SPI-DF）mixed gels.The results showed that in 0 mol/L Na Cl group,DF-10（DF/SPI=10:90）had the highest hardness,storage modulus（G’）,and disulfide bond content.However,in 0.1 mol/L Na Cl group,DF-5＿Na Cl（DF/SPI=5:95）exhibited the highest hardness and G’,and the disulfide bond content increased with the increase of DF/SPI ratio.The increase in the DF/SPI ratio resulted in the decrease of the surface hydrophobicity of SPI and the hydrophobic interaction in SPI-DF gel.In 0.1 mol/L Na Cl group,the increase of DF/SPI ratio led to the increase of protein aggregation and the proportion of free water in the gel.（2）Secondly,the effect of DF particle size(DF₁₀₀,138.7μm;DF₂₀₀,79.7μm)and transglutaminase（TGase,0.5 U/g protein）on the gel properties of SPI-DF mixture was investigated.The results showed that DF₁₀₀ displayed a better rigid-filling effect,which facilitated to improve the G’and gel hardness of SPI-DF gel,but decreased the gel cohesiveness.DF₂₀₀ had less damage to the hydrophobic interaction and cohesiveness of the gel compared to DF₁₀₀,but its large specific surface area led to a decrease in the water holding capacity of the SPI-DF gel.TGase increased the proportion ofβ-turn and the strength of gel network in DF-10（DF/SPI=10:90）,resulting in improved texture properties of DF-10 gel but a decrease in water holding capacity.However,in DF-20（DF/SPI=20:80）gel,the addition of TGase caused severe local protein aggregation and an overall decline in texture properties.Overall,DF₁₀₀-10 had the best gel properties.（3）Thirdly,based on DF₁₀₀-10 which had the best gel properties determined in the above studies,the methionine-rich PP and EW were added to improve the gel properties and amino acid patterns of the system,and the effect of PP,EW and PP-EW mixture on the gel properties of the mixed system was explored.The results showed that the size of PP aggregates was larger than that of EW aggregates.EW greatly improved the hardness,chewiness,and gelling of the mixed gels compared to PP,but the increase of EW content also led to the conversion of more immobilized water into free water.When PP and EW were added at the ratio of 1:1,the mixed gel showed the smoothest gel structure,the highest immobilized water content andβ-sheet content.The form of protein in the gel was directly related to its digestibility,and the protein digestibility of the mixed gel added with PP-EW mixture was higher than that of the mixed gel added with PP or EW alone.（4）Then,based on the above-mentioned multi-mixture system of soybean protein isolate-soybean dietary fiber-potato protein-egg white protein（SPI-DF-PP-EW）,textured soy protein was added to simulate the fibrous structure of the animal meat,and KG with different deacetylation degree（DD）were added as a binder to construct a plant-based lean meat system.The existence form of KG（KG₀,DD=0.00%;KG₁,DD=41.40%;KG₂,DD=80.01%;KG₃,DD=89.07%）in plant-based lean meat and its effect on the gel properties of plant-based lean meat were studied.The results showed that with the increase of the deacetylation degree of KG,the solubility of KG continuously decreased,and its morphology changed from fine filament to coarse filament,then to short filament,and finally to granular structure.The addition of appropriate amount of deacetylated KG was beneficial to improve the protein digestibility of the mixed gel.The regulation effect of KG on the gel properties of plant-based lean meat was closely related to its degree of deacetylation.The addition of low deacetylation KG（KG₀ and KG₁）resulted in the deterioration of gel properties of plant-based lean meat,while the addition of high deacetylation KG（KG₂ and KG₃）improved the gel properties of plant-based lean meat.Among them,1 g KG₂ had the best effect and improved the hardness of plant-based lean meat to 3307.16 g.The formula of plant-based lean meat was determined to be 11.7 g SPI,1.3g DF100,1 g PP,5 g EW,1 g KG₂,100 m L water,and 120 g textured soy protein.（5）Finally,starch-based emulsion gel was used to simulate animal fat tissue,and the effects of xanthan gum（XG）addition amount and oil/water phase ratio on gelling and cooking properties of emulsion gel were studied.The results showed that with the increase of oil phase/water phase ratio,the hardness of the emulsion gel decreased,and more oil exuded from the gel surface.The addition of XG improved the G’of the emulsion and the gel properties of the emulsion gel,and the oil leakage of the gel was alleviated.The texture and cooking properties of starch-based emulsion gel with 0.5%XG and 40%oil/water phase ratio（hardness2420.74 g and springness 0.97）were most similar to those of pig backfat.The formula of plant-based fat tissue was determined to be 4 g soy lecithin,40 g canola oil,40 g corn starch,0.5 g XG and 100 m L water.The formula of plant-based fat tissue and lean meat were mixed,and a marbled plant-based meat product were prepared by one-step heating method.The product had good formability,natural distribution of fat and thin,and maintained good shape after high-temperature frying.