Study On Properties And Application Of Egg White Protein Particle-rhamnolipid Compound Emulsions

Egg white protein particles,which have good emulsifying properties,can be prepared by egg white protein through acid-heat treatment.However,the relatively slow interfacial adsorption rate and minor emulsifying capacity limit the application of egg white protein particles in high oil phase systems.The combination of protein and small molecule emulsifiers in food can make up for the defects of single emulsifier effectively,resulting in improved emulsifying properties.Nevertheless,it is not clear about the influence of protein particle-small molecule composite emulsifiers on the properties of high internal phase emulsions(HIPEs),and the application of composite HIPEs in practical food system are absent.In this study,the interaction and interface relationship between egg white protein particles and Rhamnolipid were investigated.The properties of HIPEs in different interface compositions were analyzed,and the application efficiency of composite emulsions in nutrient delivery and plastic fat replacement were further evaluated.The specific research contents and results are as follows:Firstly,the interaction between egg white protein particles(prepared at p H 3.8 and 7.0)and rhamnolipid were investigated,as well as its effect on the properties of HIPEs.As can be seen from particle size,potential and microstructure characterization,egg white protein particles prepared at p H 3.8 had positive charge and smaller particle size,which would interact with negative-charge rhamnolipid and form complex.The egg white protein particlerhamnolipid combinations at various percentage of rhamnolipid could be divided into three regions according to the emulsifying capacity: Region Ⅰ,with egg white protein particles as the dominant on interface;Transition Region Ⅱ,egg white protein particles-rhamnolipid interface competition;Region Ⅲ,with rhamnolipid as the dominant.With increase in rhamnolipid percentage,the emulsifying ability of composite emulsifiers was significantly improved,and the maximum emulsified oil content increased from 83% to 96%.Compared with egg white protein particles at p H 7.0,egg white protein particles prepared at p H 3.8 had a stronger emulsifying ability and could combine with more rhamnolipid,which would delay the regional transition process.In region Ⅲ,the droplet size of emulsions decreased significantly as rhamnolipid reduced the interfacial tension.Egg white protein particles was mainly distributed in water phase,which could restrict the activity of water molecules effectively,thus improved the anti-coalescence stability of emulsions as stabilizers during storage.Secondly,the application of HIPEs constructed by egg white protein particles and rhamnolipid as a nutrient delivery system was explored.The curcumin loading capacity and the stability of egg white protein particles and rhamnolipid composite HIPEs in gastrointestinal environment were evaluated.As can be seen from the results,egg white protein particles as the interface dominant were more conducive to curcumin embedding and stability.In vitro digestion process,egg white protein particles and its digestive products could help stabilize emulsions morphology in stomach,while rhamnolipid could reduce emulsion droplet size during intestinal digestion,thus improved the efficiency of chylation.Combined with the experimental results of SDS-PAGE,high performance liquid chromatography and protein interface adsorption fraction,it could be seen that the addition of rhamnolipid could delay the digestion rate of egg white protein particles.During intestinal digestion,HIPEs constructed by egg white protein particles-rhamnolipid had smaller droplet size and higher peptide/amino acid interface adsorption rate,which was beneficial for improving bioaccessibility of curcumin.Finally,the emulsion gel system was constructed by introducing β-sitosterol into egg white protein particles and/or rhamnolipid composite emulsions,and its application in cookies as butter substitute was explored.The rheological and microstructure results showed that emulsion gels had a lower melting rate and faster cooling rate than butter.It made emulsion gels exhibited good plasticity,which was related to the crystallization network formed by β-sitosterol in the system.In the composite emulsion gel,egg white protein particles were helpful for stabilizing droplets in emulsion gels,while rhamnolipid could further reduce droplet size.The composite emulsion gels were used to completely replace butter in cookie system,and the texture,color measurement,geometry,oil/water migration and microstructure of dough and cookies were characterized.The results showed that emulsion gel system constructed by β-sitosterol and composite emulsifiers could help to form uniform matrix and improve the quality of cookies.At the same time,the uniform matrix structure limited the migration of oil and water during storage,thus effectively maintaining the crispness of cookies.Finally,the effects of egg white protein particles and rhamnolipid on cookies were further determined by sensory evaluation:Egg white protein particles could improve the hardness and smoothness,while rhamnolipid could improve the color and oral diffusion of cookies effectively.Cookies prepared by egg white protein particles,rhamnolipid and β-sitosterol emulsion gels could obtain closest physicochemical,structural and sensory properties to butter cookies.Therefore,the emulsion gel prepared by egg white protein particles,rhamnolipid and β-sitosterol could be regarded as a potential plastic fat substitute.