Preparation And Properties Of Pickering Emulsion Stabilized By Extruded Esterified Modified Starch

Rice starch the natural carbohydrate material can be used as emulsifier of the Pickering emulsion because of the small particle size.However,natural rice starch has poor hydrophobicity and is difficult to stabilize the Pickering emulsion.At present,most of them are modified by octenyl succinic anhydride(OSA),but dodecenylsuccinic anhydridee(DDSA)has longer carbon chain and the Starch Sodium Dodecenyl Succinate(SSDS)has better hydrophobicity and has the potential of forming more stable Pickering emulsion.The common method of synthesizing SSDS is wet synthesis,but the wet method has long modification time and low reaction efficiency,while the extrusion method has simple process,high reaction efficiency and friendly environment.In this paper,using rice starch as raw material,SSDS was synthesised by extrusion method.The stability and other characteristics of Pickering emulsion stabilized with SSDS were studied.Using rice starch as raw material,the extrusion conditions of preparing Starch Sodium Dodecenyl Succinate(SSDS)were studied.The effects of different extrusion such as temperature,moisture content,screw speed and the amount of dodecenyl succinic anhydride on the substitution degree(DS)and particle size of SSDS were studied.The results showed that SSDS had smaller particle size and the highest DS value when temperature was 120 ?,screw speed was 275 rpm,water content was43.75%,DDSA content was 5%.The results of SEM,XRD,viscosity and DSC analysis showed that compared with the natural rice starch,the crystal structure of extruded SSDS was destroyed and the particle morphology was completely changed.Pickering emulsion with high stability(O/W)was prepared by using SSDS as emulsifier.The effects of starch concentration,oil concentration,pH and salt concentration on the stability of emulsion were studied.The stability mechanism of emulsion was investigated by observing the microstructure and droplet size of emulsion.The results showed that Pickering emulsion was the most stable when starch concentration was 2.5%,oil concentration was 60% and pH was 5.Salt concentration has a significant effect on emulsion stability.The DS value and particle size of SSDS are the important factors to Pickering emulsion stability.The larger the DS and thesmaller the particle size of SSDS,the more stable the Pickering emulsion is.Through the analysis of optical microscope and laser confocal microscope,it can be seen that SSDS particles are adsorbed on the oil / water interface,enveloping the oil drop,forming a physical barrier on the surface of the oil drop to prevent the droplet from flocculation and coalescence.The drug-loading abilities and storage stabilities of Pickering emulsion were investigated by using curcumin and coumarin as model functional factors.The release characteristics of Pickering emulsions were explored through simulating the gastrointestinal tract environment.The scavenging abilities and anti-tumor activities of functional Pickering emulsions on DPPH and ABTS radicals were studied.The results showed that functional Pickering emulsion could release functional factors slowly in gastrointestinal fluid.The larger the DS and the smaller the particle size of SSDS,the more stable the functional materials loaded by Pickering emulsion were,and the slower the release rate of functional materials.With the increase of the concentration of drug-loaded Pickering emulsion,the scavenging rate to two kinds of free radicals can reach more than 80%.Through the cytotoxicity evaluation,drug-loaded Pickering emulsions have good inhibitory effects on the proliferation of MCF-7 and Hela two kinds of cancer cells.