Preparation,Structural Characterization And Application Of Egg White Protein/Sodium Carboxymethylcellulose Conjugated Aerogel

Aerogel is a traditional porous material,and several proteins have been developed and used for the preparation of protein-based aerogels.EWP,as an important component of avian egg protein,has excellent gel properties.However,the aerogels prepared by drying a single EWP gel network have poor mechanical properties and low oil loading efficiency.Therefore,the modification of EWP aerogels is an urgent problem to be solved.Researchers mainly have been improving the structure and properties of protein gels/ aerogels by physical modification(temperature,pressure,metal ions,etc.),chemical modification(p H,glycosylation,phosphorylation,etc.)and enzymatic modification(enzymatic digestion,enzymatic cross-linking,etc.).In this paper,we adopt the more mature and economical glycosylation modification method to optimize the preparation process of EWP aerogels,investigate the characterization of EWP/CMC-Na conjugated aerogels and apply them to antimicrobial packaging by introducing CMC-Na.The optimal preparation process of EWP/CMC-Na conjugated aerogels was obtained mainly by orthogonal tests with mechanical strength and oil loading capacity as the assessment indexes,and on this basis,the physicochemical properties of EWP/CMC-Na conjugates and their conjugated aerogels were investigated in terms of microscopic morphology,mechanical properties,pore properties,emulsification properties and oil loading properties.The antibacterial properties,release characteristics and storage properties of thymol in EWP/CMC-Na conjugated oleogels were also investigated.The main research results are as follows.(1)The aerogels were prepared by optimizing the EWP/CMC-Na dry heat Maillard reaction conditions(CMC-Na addition,dry heat temperature,dry heat time)and the gelation conditions(gelation p H and gelation temperature).The results of the orthogonal tests showed that when the CMC-Na addition was 2.5% of EWP,the dry heat temperature was 60 ℃,the dry heat time was 12 h,the gelation p H was 11 and the gelation temperature was 85 ℃,we obtained the best EWP-based aerogel with the mechanical strength of 2.75 MPa and the oil loading capacity of 5.71 g/g.(2)The amino group on EWP and the carbonyl group of CMC-Na were covalently cross-linked by the Maillard reaction to form a more uniform and delicate threedimensional mesh structure.The properties and structures of the conjugates and its aerogels were investigated by characterizing the properties and structures of them and analyzing the microscopic and macroscopic aspects of the EWP aerogels,we further elucidated the intrinsic mechanism of CMC-Na to improve the structure of EWP and significantly enhance the mechanical and oil loading properties of EWP aerogels by conjugated cross-linking.(3)As a semi-solid system consisting of a network structure formed by a polymer and a hydrophobic liquid(e.g.oil),the oleogel not only has a high encapsulation efficiency,but also enables the encapsulated material to have good slow release properties.Experiments indicated that thymol in EWP/CMC-Na conjugated oleogels as carrier matrix had antimicrobial activity against both S.aureus and E.coli;Thymol was continuously released from oleogels through slow release,and still has antimicrobial properties while the release rate is slow;The low temperature(4 ℃)can significantly reduce the moisture absorption rate of the oleogel and prolong its storage time up to 5days.At the same time,the effective retention rate of thymol in the oleogels could be maintained for a long time,up to 15 days.