Study On Soy Protein Modified Prefabricated Powder Suitable For Microwave 3D Printing

Protein has been wildly used in food 3D printing because of its nutritional and functional properties,and it has a wide range of application prospects.Materials that are suitable for 3D printing need to meet some certain physical and chemical characteristics,such as suitable fluidity and rigidity.However,most protein-based food materials,especially globulin,do not possess these characteristic.As a result,a pretreatment process is necessary to improve the printability of food materials that are not suitable for 3D printing.In this paper,we choose soy protein as our research object,because it is commonly used in food industry and it is unsuitable for 3D printing in its natural state.Based on the microwave 3D printing technology,the printability and microwave gelling characteristics of soy protein were improved by pretreatment,the compatibility between the physicochemical characteristics of printing pastes and microwave 3D printing effects was studied.Next,the effects of pretreatment on the structure of soy protein and the mechanism of the formation of soy protein gels were explored.In this study,we fabricated a prefabricated powder that could achieve self-gelling through microwave 3D printing after a simple rehydration process.The main research contents and results are as follows:(1)Study on the compatibility between physicochemical properties of soy protein and microwave 3D printing effects.Soy protein pastes with different physicochemical properties were prepared to study the compatibility between physicochemical properties and microwave 3D printing effects.The printability of the materials was divided into extrudability,shape stability and microwave instant gelling characteristics.The rheological properties,dielectric properties,thermal gelling properties and gel properties of the material were tested,and the physicochemical properties range of the microwave 3D instant gelling was determined.For extrudability,the printing pastes could be extruded smoothly when theτ_fis 1500～4000 and the n value is 0.038～0.184.As for the shape stability,the pastes could form a good shape after 3D printing at room temperature when theτ_yvalue is 90～250 Pa,the shear recovery rate>88%;the printed products have good shape stability during MW 3D printing when a value is 10000～300000,and the initial G’is 12000～40000.For microwave instant gelling characteristics,the pastes could achieve instant gelling when the gel temperature is within the extrusion temperature range,and the gel time is 10～25s.Soy protein pastes that meets the above physical and chemical conditions could achieve instant gelling after microwave 3D printing.(2)The mechanism of improving the microwave 3D printing characteristics of soy protein by pretreatment.With the increase of pretreatment degree,the tertiary structure of soyprotein unfolds,and hydrophobic groups were gradually exposed,forming a fibrin-like structure.After microwave3D printing,the pretreated soy proteins aggregated to form a stable three-dimensional network gel structure.The optimum pretreatment degree of soybean protein was 57%.Through the analysis of chemical force,it is found that theε-(γ-glutamine)covalent bond formed by transglutaminase and microwave is the main force driving the formation of gel network structure.Pretreatment exposed more action sites of TGase,which leads to the instant gelling of printing pastes in microwave 3D printing.However,excessive pretreatment may lead to excessive gelation of soy protein,resulting in the formation rough structure.(3)Microwave 3D printing for the rehydrated pastes of soy protein prefabricated powderIn this section,the pretreated soy protein pastes with ideal printing effect in the early stage were freeze-dried,pulverized,rehydrated and microwave 3D printed,and the printing effects of the rehydrated soybean protein pastes were explored.The effect of powder particle size and rehydration time on the printing effect of rehydration pastes was investigated.Due to the weak water holding capacity of the rehydrated pastes,the viscosity and G’of the precast powder rehydration system decreased significantly compared with the pastes before freeze-drying.With the decrease of particle size,water holding capacity,initial viscosity and energy storage modulus of slurry increased.With the extension of rehydration time,the rheological properties of the rehydration pastes and the formability of the printed product were gradually enhanced,and there was no further property change after 90min.The soy protein powder prepared by 270 mesh sieve and rehydrated for 90 minutes achieved instant gelling after microwave 3D printing,which verified the feasibility of microwave 3D printing of soy protein prefabricated powder rehydration system.