Preparation Of High Internal Phase Emulsion Based On Polysaccharide And Its Application In 3D Printing

Extrusion-based 3D printing is an emerging additive manufacturing technology spawned by burgeoning food processing and manufacturing.It can simplify the tedious process of traditional processing,realize the personalized design of product appearance,and customize precise nutritional meals,thus promoting the food processing industry to enter the“Internet+”high-speed development mode.The use of high internal phase emulsions as food inks has become a novel development direction due to their appropriate rheological properties and ability to carry natural edible ingredients and specific nutrients,which contributes to broadening the scope of future inks designed for personalized nutrition,driving 3D printed products into the daily diets of consumer groups such as soldiers,astronauts,athletes,pregnant women,teenagers and children,patients and elderly people with swallowing difficulties.To obtain better molding effect and higher nutritional value,the extrudability,recoverability,self-supporting properties and nutrient delivery ability of high internal phase emulsions need to be further improved.In this paper,polysaccharide（β-cyclodextrin）was selected as the main emulsifier to modulate the physicochemical properties,3D printing quality,color conversion effect and delivery capability of high internal phase emulsions by introducing chitosan and changing p H value,thereby promoting the application of high internal phase emulsions in 3D printing and further satisfying the individual needs of specific consumer groups（e.g.,vegetarians and people with protein allergies）.The main research contents are as follows:（1）The effect of the aqueous phase environment on the 3D printing ability ofβ-cyclodextrin-based high internal phase emulsions was investigated.The effects ofβ-cyclodextrin concentration,p H value and ionic strength on the interfacial behavior,microstructure,rheological properties and 3D printing quality of the high internal phase emulsions were evaluated comprehensively.The results showed that high internal phase emulsions could be prepared at appropriateβ-cyclodextrin concentrations（0.6 wt%-1.5 wt%）,p H values（3-7）and ionic strength（25 m M-400 m M Na Cl）.The increase ofβ-cyclodextrin concentration and the decrease of p H value all contributed to the adsorption ofβ-cyclodextrin molecules at the oil-water interface,which improved the microstructure of the emulsions and led to a tighter inter-droplet buildup,thus showing higher printing potential in rheological tests and exhibiting better molding effect in 3D printing.These results are helpful to guide the application ofβ-cyclodextrin stabilized high internal phase emulsions in 3D printing and promote the synergistic development of 3D printing technology and high internal phase emulsions.（2）3D printing properties ofβ-cyclodextrin-stabilized high internal phase emulsions were further improved by using chitosan-modifiedβ-cyclodextrin via hydrogen bonds and electrostatic interactions.The most promising 3D printing inks were screened fromβ-cyclodextrin/chitosan stabilized high internal phase emulsions at chitosan concentrations of0.08 wt%-0.40 wt%and aqueous phase p H range of 3-7.The results indicated that theβ-cyclodextrin/chitosan complexes formed by 1.20 wt%β-cyclodextrin and 0.32 wt%chitosan at p H 5 had suitable wettability and interfacial tension,and enabled the formation of a protective film at the interface,which hindered the coalescence of emulsion droplets through electrostatic repulsion and steric hindrance effects.The rheological results demonstrated that the high internal phase emulsion under the above conditions exhibited excellent printing potential in three stages of 3D printing:the extrusion stage（shear thinning behavior）,the recovery stage（excellent shear recovery and creep recovery properties）,and the self-supporting stage（sufficient storage modulus and yield stress）.The subsequent 3D printing results illustrated that this high internal phase emulsion was capable of printing objects with high precision,high resolution and high fidelity.These findings provide ideas and guidance for the application of polysaccharide-based high-internal phase emulsions in 3D printing.（3）Theβ-cyclodextrin-based high internal phase emulsions were prepared using p H-sensitive curcumin and heat-labile Na HCO₃and then constructed butterfly shapes by 3D printer.After heating the butterfly shapes at 85°C for 10 min,the color of the butterfly changed from bright yellow to reddish brown.This was because the heating caused the decomposition of Na HCO₃to Na₂CO₃in the aqueous phase,which increased the p H value of the system and the oil-water interface,thus causing the change of curcumin conformation.Meanwhile,the changes in heating temperature,heating time and Na HCO₃concentration would have different effects on the degree of the color change of the printed samples.In addition,the introduction of chitosan and changing the p H value of the aqueous phase allowedβ-cyclodextrin-stabilized high internal phase emulsions to have a more defined butterfly texture after heating.These findings take full advantage of personalization and customization in 3D printing technology and enrich the application scenarios of HIPEs in 3D printing.（4）The stability and bioaccessibility of the loaded curcumin were investigated using the polysaccharide-based high internal phase emulsions prepared above as carriers.The results showed that the microstructure and rheological properties of theβ-cyclodextrin-based high internal phase emulsions loaded with curcumin could be modulated by changing the p H and introducing chitosan.Meanwhile,the thermal stability of theβ-cyclodextrin/chitosan-based high internal phase emulsions loaded with curcumin was superior to that of theβ-cyclodextrin-based high internal phase emulsions loaded with curcumin.These phenomena might be mainly attributed to the physical interactions betweenβ-cyclodextrin and chitosan that enhanced the ability ofβ-cyclodextrin to stabilize curcumin droplets.Moreover,the chitosan in the aqueous phase contributed to enhancing the viscosity of the high internal phase emulsions.In addition,the loading of curcumin reduced its degradation under natural light exposure and improved its stability and bioaccessibility after the gastrointestinal digestion stages,thus enhancing the delivery properties of the polysaccharide-based high internal phase emulsions as the 3D printing inks and giving full play to the dual advantages of high internal phase emulsions and 3D printing technology.