Research On Extrusion-based 3D Printing Based On Brown Rice Gel

3D printing technology has expanded the traditional processing methods,making food processing personalized,which will bring new development opportunities to catering and retail food industry.Food materials are as basis for 3D printing technology and it is also an important factor restricting the wide application of 3D printing technology in food industry.Most traditional food materials are facing difficulties that they are not suitable for 3D printing or with low printing quality.Therefore,the exploitation of food materials and the improvement of materials and process are the primary tasks to promote the development of 3D printing.In this paper,brown rice was used as raw material to explore the effect of drying method on the physicochemical properties and rheological properties of brown rice flour.Considering the printing feasibility of brown rice gel,the best drying method was determined.Based on this,brown rice flour was made into gel and the printing characteristics of gel were further improved by adding hydrocolloids in order to create complicated structure.Then the flow path in the barrel was simulated and analyzed during the material extrusion process,providing theoretical guidance for material selection.And effects of printing process parameters on the printing behavior and quality properties of the brown rice gel were explored.This study lays a theoretical foundation and practical application basis for the application of extrusion-based 3D printing technology in food industry.Firstly,effects of drying methods,hot air drying(HAD),microwave drying(MVD),vacuum freeze drying(FD),pulse microwave vacuum freeze drying(PSMFD)on the physicochemical properties and rheological properties of brown rice flour were studied.Results showed that the basic components and nutrients of brown rice flour were the best retained by FD and PSMFD.And the rheological results showed that the brown rice flour obtained by different drying methods had the shear thinning behavior,which met the basic condition for 3D printing.In especially,the brown rice flour obtained by FD and PSMFD had higher viscosity and mechanical strength.Compared with FD,PSMFD shortened the drying time by 62.50% with higher efficiency.Secondly,effects of xanthan gum(XG),guar gum(GG),xanthan-guar gum mixture(XGGG),Sodium carboxymethyl cellulose(CMC)and agar(AG)on the rheological properties,texture properties,microstructure and 3D printing properties of brown rice gel were explored.The printing behavior and deviations of different printed samples were compared and the stability of products printed by the optimized formula was evaluated.The results showed that samples added XG-GG mixture exhibited the best performance on printing behavior,and it had good shear-thinning properties,relatively high elastic modulus and low strain,strong mechanical strength and self-support ability.The microstructure of XG-GG also showed that it was more tightly connected and smooth than other samples without obvious fracture,in corresponding to less dimensional deviation of printed hollow cylinder(0.76% and-2.96% in diameter and height,respectively)and good stability within 12 h.Thus,brown rice gel added XG-GG was suitable for creating complicated structure during 3D printing.Then,the inner flow channel of the barrel was simulated to know parameters which were not easily obtained in the barrel.And effects of adjustable process parameters such as printing height,nozzle diameter,nozzle moving speed,extrusion level and relative position of the two nozzles on the printing behavior of the brown rice gel were explored.Results on simulation showed that with the width of the flow channel decreasing,the flow velocity of the material changed from slow to fast,the pressure from large to small,the shear rate from small to large,and the viscosity from large to small,which were beneficial to stable extrusion of materials.The results showed the optimal printing parameters were as followed: nozzle diameter 0.84 mm,initial height 0.84 mm,layer height 0.84 mm,nozzle moving speed 25 mm/s,and extrusion level 100% for one nozzle used.When two nozzles used,the initial relative position of the double nozzle was x=66.50 mm,y=0.80 mm,and other parameters were consistent with the one nozzle used.Finally,the effects of three variables,nozzle diameter,perimeters,and infill density on the dimensional and texture characteristics of the 3D printed sample were investigated using a response surface test.Results showed that the nozzle diameter had a great influence on the dimensional characteristics of the printed sample.The decrease of nozzle size from 1.56 mm to 0.84 mm used to print objects resulted in the increase of height from 14.78 mm to 16.25 mm and a decrease of diameter from 32.84 mm to 30.40 mm,which was closer to the designed one with less deviation.The perimeters had a positive effect that both the height and diameter of the sample increased with the perimeters increased.And the infill density had no effect on that.The texture properties of samples were significantly related to infill density,followed by perimeters and nozzle size(P<0.05).The hardness and gumminess of the printed sample decreased significantly with the decrease of nozzle diameter,perimeters and infill density(P<0.05).