Modification Of Cellulose Nanofibrils And Its Application In Stabilizing Emulsion

Pickering emulsion,which uses solid particles as stabilizers,is popular among researchers for its excellent stability,green and non-toxicity.Cellulose is the natural polymer polysaccharide that is renewable and abundant in nature.After mechanical and chemical treatments,cellulose can be endowed with the advantages of nanomaterials.It has the advantages of good biocompatibility,non-toxicity,and degradability,so that it is an ideal Pickering emulsion stabilizer.In this paper,cellulose nanofibrils(CNFs)were used as raw materials,and different modification reagents were used to enhance their hydrophobic properties,in order to improve the stability of CNFs in emulsions.Firstly,methyltrimethoxysilane(MTMS)was used to modify CNFs,and the most suitable modification process for CNFs by MTMS was discussed.When the system temperature was 25℃,p H 5,and the reaction time was 2 h,the water contact angle of CNFs after modification increased by 93.1±0.6°.The modified products(M-CNFs)were compared and characterized by Fourier infrared spectroscopy,X-ray diffraction analysis,and thermogravimetric analysis.And then,Pickering emulsions with M-CNFs as stabilizer were prepared,and the stability performance of the emulsion under different conditions of MCNFs concentrations,oil-water ratio,p H,and Na Cl concentrations were studied.Compared with CNFs,emulsions prepared by M-CNFs had a smaller and more concentrated droplet size distribution,and a higher absolute value of ζ-potential,which was more conducive to the preparation and application of Pickering emulsions.Secondly,dodecenyl succinic anhydride(DDSA)was chosen,to modify CNFs through esterification.It was determined through experiments that the most suitable modification process for CNFs by DDSA was system temperature 40℃,system p H value 8.5,and reaction time 6 h.The water contact angle of CNFs after modification increased by 83.2±0.9°.The modified products(D-CNFs)were compared and characterized by Fourier infrared spectroscopy,X-ray diffraction analysis,and thermogravimetric analysis,which proved the successful reaction of the modification.Pickering emulsions with D-CNFs as stabilizer were prepared,and the stability of the emulsion under different conditions of D-CNFs concentrations,oil-water ratio,p H,and Na Cl concentrations were studied.Through comparative experiments with CNFs,it was shown that the emulsions prepared by D-CNFs had better stability.The experiment found that the stability of D-CNFs in Pickering emulsion is better than that of M-CNFs.Therefore,D-CNFs were introduced into the simulated food emulsion system containing insect protein,and the stability performance of the simulated emulsion system under different conditions of D-CNFs concentrations,D-CNFs and insect protein ratio,oil-water ratio,p H,and Na Cl concentrations were studied.The experimental results showed that the D-CNFs concentrations in the water phase increases within a certain range,which enhanced the stability of the simulated emulsion system.Increasing the ratio of insect protein was not conducive to the stability of the emulsion.In the experiment,the ζ-potential value of the emulsion is under the combined action of D-CNFs and protein,which showed a trend of decreasing with the increase of p H.To investigated whether the addition of D-CNFs have effects on the digestion and absorption of oil in the emulsion,an in vitro digestion simulation was carried out.It was found that the final fat digestibility of the emulsion after adding D-CNFs was lower than that of the emulsion without D-CNFs,indicating that DCNFs could promote the inhibition of lipid absorption,or could be used for the development of specific functional foods.