Studies On The Modifications Of Arabinoxylan Corn Fiber Gum And Its Emulsion Stability And Interfacial Rheology

China has been the largest consumer and second largest producer of corn for many years.In 2019,China's corn consumption and yield reached 275 and 261 million tons,respectively.Corn fiber is a low-valued coproduct of the corn milling process,which generally accounts for about 20% of the raw materials.Corn fiber gum(CFG)is a natural polysaccharide extracted from corn fiber,with a highly branched arabinoxylan structure.CFG has great potential to replace gum arabic as an emulsifier,thickener,adhesive,film-forming agent,etc.It is a renewable natural resource with good development prospects.As a natural,non-toxic,environmentally and economically friendly polysaccharide emulsifier,CFG fulfills the requirements of ‘clean label' and growing stringent consumption demand.At present,the related researches on the functional properties of CFG mainly focus on its emulsifying properties.Emulsions are complex systems with multiscale structure.The correlations among different scales,especially the role of the interfacial rheological properties at the microscopic scale in the bulk emulsion stability at the macroscopic scale,remain unclear.Therefore,it is of great theoretical significance and application value to study the correlation between the interfacial properties and the bulk emulsion properties by using multiscale approach.In addition,the stability of protein colloids has also been a technical challenge in the food or beverage industry.It is also of great significance to extend the knowledge about the interactions between polysaccharides and proteins,as well as stabilization mechanisms,thus providing useful information on the development of plant protein-based beverage formulations.In this dissertation,based on two kinds of CFG derivatives successfully prepared through chemical modifications,and the applications of these two modified products in stabilizing oil-in-water emulsions,plant protein dispersions,and hydrophobic active substances,we have focused on the study of the emulsification of the derivatives,especially the relationship between the interfacial rheological properties and the bulk emulsion stability.The detailed contents and conclusions are as follows:1.In order to further improve the physicochemical properties of CFG and widen its application fields,we first hydrophobically and hydrophilically modified CFG.A series of octenyl succinate anhydride(OSA)modified CFG(OSA-CFG)with different degrees of esterification(DE,0?6.1%)and carboxymethylated CFG(CMCFG)with different degrees of substitution(DS,0?0.69)were successfully prepared,respectively,and detailed structural characterization was carried out.2.By using OSA-CFG samples with different DEs as model emulsifiers,multi-techniques,as well as a multiscale approach,the relationship between the interfacial rheological properties and the bulk emulsion stability were revealed,and the stabilization mechanisms were clarified.Compared with native CFG,the introduction of hydrophobic groups endowed OSA-CFG with higher efficiency in reducing the oil-water interfacial tension,forming thicker interfacial films with higher interfacial elasticity and viscosity,as well as preparing emulsions with smaller droplets and better bulk stability.Coupling analysis results among different scales showed that the emulsion stability correlated well with the droplet size;a decent correlation was also found between the interfacial viscoelasticity and the bulk emulsion stability.This work was the first to combine the conventional rheometer with QCMD to investigate the interfacial rheological properties of polysaccharide emulsifiers.The accessible frequency range was enlarged,and important rheological parameters were obtained.We demonstrated good agreement of the macroscopic and microscopic techniques.Using multi-techniques and a multiscale approach,the present work effectively correlated the interfacial rheological properties of native and esterified CFG to the bulk emulsion stability.The correlation provided theoretical guidance and technical approaches for effectively predicting and controlling the bulk system properties by tuning the interfacial rheological properties.3.We compared the effectiveness of CMCFG with CFG,high-methoxy pectin(HMP),sodium carboxymethyl cellulose(CMC)and konjac glucomannan(KGM)on the improvement of the physical stability of PPD,and analyzed their different stabilization mechanisms in detail.By comparing the particle size,zeta potential,apparent viscosity,and instability index,we studied the effects of type,DS and concentration of the polysaccharides,as well as p H on the stabilization behavior of PPD.It was found that all these polysaccharides could improve the stabilization of PPD.The electrostatic repulsion,steric hindrance effect and high viscosity of continuous phase were main contributors to stabilize the systems.Due to the low viscosity of the CFG solution,a high concentration(? 10%)was needed to obtain a good stability of PPD,whereas HMP,CMC and KGM could well stabilize PPD at lower concentrations(? 1%).Results also showed that a certain level of carboxymethyl modification could effectively enhance the effectiveness of CFG on stabilizing PPD,thus improving the utilization of CFG.These results extended the knowledge about the stability of protein induced by polysaccharides,thus providing useful information on the development of plant protein-based beverage formulations.4.A new type of plant-derived composite nanoparticle containing pea protein concentrate(PPC)and CMCFG was successfully prepared,and its ability to encapsulate and control the release of curcumin(Cur)was studied.The Cur-loaded complexes prepared at p H 7.0 or 3.5 exhibited enhanced thermal and chemical stability,bioaccessibility,and controlled release behavior of encapsulated Cur.In addition,the Cur in core-shell complex showed better water solubility and antioxidant activity than free Cur in water.These results suggested that the complexes formed by plant-derived PPC and CMCFG had great potential as vehicles for the encapsulation and delivery of Cur,thereby showing potential for applications in the food,cosmetic,and pharmaceutical industries.