Surface Modification Of Microcrystalline Cellulose (MCC) And Properties Of Its Pickering Emulsion

Because of its unique crystal structure,stable thermal properties and excellent mechanical properties,microcrystalline cellulose(MCC)is widely used in the fields of functional composite materials,drug excipients,controlled release of active ingredients,and low-sugar and low-fat foods.The preparation of Pickering emulsion with nano-scale cellulose(NCC)is a research hotspot in active material-encapsulated and functional foods currently,but the high price of NCC limits its widespread use in the food field.Therefore,in this paper,a green and low-cost method for preparation of amphiphilic cellulose(LA-MCC)was explored by mechanical grinding and ethanol solvothermal process.In this method,MCC was hydrophobic modified by lauric acid(LA)while reducing the particle size of MCC.Pickering emulsions were prepared with LA-MCC particles.The co-construction of methylcellulose(MC)and LA-MCC to build a stable emulsion in an acidic environment was studied.Meanwhile,the preparation method of magnetic amphiphilic cellulose(LA-FE-MCC)was studied and its emulsion properties were analyzed.The main research contents are as follows:(1)Preparation of LA-MCC particles by lauric acid(LA)modified MCC: Particle size,specific surface area and reactivity of MCC were regulated by mechanical grinding under alkaline conditions.The ethanol solvothermal process enhanced the esterification of MCC by LA and prepared an amphiphilic LA-MCC particle.The contact angle of modified MCC increased from 55° of original MCC to 84° of LA-MCC,showing amphiphilicity.Emulsion prepared with 1.5%(w/v)LA-MCC and 3:7(v/v)corn oil exhibited a Zeta potential of-58.7 mV under neutral pH of 7,showing good stability.Emulsion index only decreases by 1.66% after seven days,and the emulsion remains stable after 50 days.(2)MC and LA-MCC as co-stabilizers to construct stable acidic Pickering emulsions: The molecular interaction between MC and LA-MCC was enhanced by high-speed homogenization to construct strong interfacial barriers and three-dimensional gel network structures in emulsions.MC with a molecular weight of 120 kDa exhibited strong gel properties,which was beneficial to improve the emulsion stability under acidic conditions.Emulsion index was greater than 65% after 30 days,and the appearance,stability and rheology of the emulsion were improved.(3)Preparation of LA-FE-MCC and its Pickering Emulsion: Magnetic cellulose(FE-MCC)was prepared from ferrous sulfate solution by co-precipitation method.LA-FE-MCC particles were prepared by using ethanol solvothermal process to enhance the esterification of LA-MCC with LA.The effects of LA-FE-MCC particle concentration and pH value on its emulsion properties were studied.MC was used to suppress the aggregation of LA-FE-MCC particles and improve its dispersion stabilities.The results show that the contact angle of LA-FE-MCC is 90.5°,which is the ideal particle for constructing Pickering emulsion.Emulsion prepared with 0.8%(w/v)LA-MCC and 1:1(v/v)corn oil exhibited good stability and magnetic response.When the oil-water ratio is 7:3(v/v),the emulsion can undergo phase inversion,resulting in a water-in-oil(W/O)emulsion.When the water phase contains a certain amount of MC molecules,it cooperates with LA-FE-MCC particles to construct a gel-like emulsion,which inhibits the movement of droplets,increases the viscosity of the emulsion,and improves the stability of the emulsion.