Design Of Curing Unit Of Microwave 3D Printing And Study Of Printed Surimi Products Quality

In 3D food printing,most food materials have high moisture content,strong fluidity,and lack of mainstream curing characteristics such as UV-curing and hot melt,so printed products are prone to deformation,collapse,and flow.The primary solution is to adjust the components of the slurry.Although these methods effectively improve the molding quality of products by optimizing the rheological properties and solid-like behaviors,the products after printing are still fluid dynamic materials.And there is no way to avoid deformation factors during printing and post-processing.Therefore,this article develops microwave 3D printing curing unit by constructing a multi-physics simulation model.The 3D food printing adapting material,surimi,was selected as the printing system.Finally,according to the thermal response of myofibril protein and transglutaminase(TGase)in surimi,explore the gelation mechanism in the process.This research aims to provide a theoretical basis and effective means for the instant curing of thermal gel food during the printing process.The main research contents and results are as follows:(1)Heating method design and computer simulation of curing unit of microwave 3D printDesign heating methods,and verify the situation of heating and extrusion based on multiphysics simulation technology.In the conduction heating mode,the temperature distribution of the slurry in the extrusion nozzle showed a "V" shape,and the temperature at the pipe wall was higher than the temperature at the center of the extrusion nozzle.Both strong shear thinninglow thermal conductivity slurry and weak shear thinning slurry had higher viscosity at the pipe wall.In the implanted microwave heating mode,the transmission distance of microwave was short,and the heating capacity was weak.Parallel wires and spiral microwave heating mode can lead microwaves out of the coaxial patch cord,so that high field microwaves were distributed near the antenna and targeted heating is realized.The shortening of the distance between the antenna and the extrusion nozzle and the increase of the antenna length reduced the microwave dissipation and improve the heating effect.At the same outlet temperature,the temperature distribution and extrusion effect of these two modes were not much different,but the heating efficiency of the spiral microwave heating mode was higher.The temperature distribution is not affected by the shear thinning properties and thermal conductivity,and there is no phenomenon of high wall temperature.The viscosity distributions of the four slurries all show a trend of gradually decreasing from the center line to both sides.(2)The effect of microwave 3D printing on the printing of surimiIn the microwave 3D printing,the surimi can maintain good pseudoplasticity at appropriate microwave powers(0 W/g?50 W/g).Simulation results showed that the change in microwave power affected the extrudability by changing the temperature distribution of surimi in the nozzle.The molding quality of surimi products has been significantly improved with the increase of microwave power,and hollow spherical products with better shapes can be formed.After printing,the surimi products formed solid gel at 40 and 50 W/g when TGase is added,and the value reached 217.51 ± 12.37 g·cm and 327.80 ± 18.15 g·cm,respectively.The heights of these products were 29.15 ± 0.05 mm and 29.29 ± 0.09 mm,which were the closest to the height of the model(29 mm).And the internal hollow area maintained a good arc shape after cutting and placement.Moreover,the cut section shows that adhesion occurred between each layer of the solid gel products.This means that the gel-curing of surimi occurred during selfgelation in the deposition process.(3)The mechanism of the gel-curing of surimi during microwave 3D printingScanning electron microscopy images clearly indicate that the synergistic effect of microwave and TGase promoted protein aggregation and formed "bridges" between proteins.With the increase in the microwave power,the hydrogen bonds content of the surimi products increased significantly,while the ionic bonds decreased.At 60 W/g,the clog occurd in the nozzle,the surimi was overheated,the content of disulfide bond and hydrophobic force were significantly increased,and the content of sulfhydryl group was significantly decreased.SDSPAGE results showed that the myosin heavy chain(MHC)bands almost disappeared at 40,50,and 60 W/g with TGase.No significant changes occurred in the other bands.At the same time,the protein solubility of these groups of samples was significantly reduced.