Construction Of Co-assembly Hybrid Composites By Rice Proteins And Walnut Proteins And Its Application In The Preparation Of High Internal Phase Emulsions

Compared with the process of obtaining plant proteins,the production process of animal proteins needs more land and freshwater resources,and emits more greenhouse gases at the same time,which is not constant with the concept of sustainable development.What’s more,the dietary pattern based on animal proteins has been proved to be related to the high incidence of chronic non-communicable diseases.Therefore,the exploitation of plant protein resources is one of the hotspots in food science.Unfortunately,most plant proteins have extremely poor aqueous solubility,which strictly limits their further application in the food industry.This research chooses rice proteins(RPs)and walnut proteins(WPs)as the objects.RPs are a by-product of the rice starch(sugar)industry,while WPs are a by-product of the walnut oil industry.Both proteins have high gluten content,therefore exhibit extremely low aqueous solubility under neutral conditions.Existing researches focused on the improved solubility of both proteins mainly based on the traditional methods,such as enzyme reaction,Maillard reaction,and ultrasonic modification.However,both physical,chemical,and enzymatic reactions have limitations and what’s more important,cannot achieve simultaneous solubilization of both proteins.In this study,the co-assemble hybridization technology was used to achieve the simultaneous solubilization of two hydrophobic proteins,RPs,and WPs.This result was achieved by dissolving the two proteins at p H12 to fully unfold their structure prior to neutralization.The solubility of RPs was boosted to 97.5% ± 2.2% while WPs were completely solubilized by adjusting the ratio of RPs to WPs(R/W)to 1:2(w/w).The primary structure of the both proteins was retained entirely.The results from electron microscope showed that the protein composites(R/W = 1:1,w/w)exhibited a relatively uniform spherical morphology(≈ 100 nm)while the hydrophobic aggregates were broken.The results from the dynamic characterization of refolding process of protein composites showed that the addition of WPs has a switch to the structure of protein hybrid-bodies.The rigidity of the protein hybrid-bodies made the proteins embed hydrophobic groups and exposed hydrophilic groups under neutral conditions.Adequate surface charge(zeta-potential <-35 mv)supported the high colloidal stability of the protein composites.Inspired by the combination of two hydrophobic macromolecules through non-covalent interactions forming a hydrocolloid,this technology was applied to the construction of a novel delivery system for an alkali-soluble hydrophobic active substance,apigenin.After the same treatment,encapsulation efficiency of 91.22%±1.07% while a loading capacity of 98 μg/mg±2μg/mg can be achieved under the optimal preparation conditions(R/W = 1:1.5,w/w,initial protein concentration 1%,initial apigenin concentration 0.1%,w/v).The apigenin-loaded protein composites with a uniform(≈100 nm)spherical shape has a good solubility in water(10 mg/m L).In vitro simulated gastrointestinal digestion experiments showed that the bioavailability of apigenin after encapsulation boosted from 15.72%±2.15% to52.72%±1.46%,proving the reliability of the loading system.Finally,considering the structural properties of the protein composites,the potential of using it as a stabilizer for high internal phase Pickering emulsions(HIPPEs)was investigated.Furthermore,an attempt was made to develop a whole plant-based walnut-mayonnaise with the features mentioned above.When protein concentration(c)and oil volume fraction(Φ)reached 2%(w/v)and 75%(v/v)repectively,HIPPEs showed self-supporting properties and strong resistance to stress.It can remain stable even after being heated at 95 ℃ for 30 min,which showed that the protein composites had good soft particle-based Pickering stabilizer performance.Enhanced ionic strength(I > 50 mmol/L)gave HIPPEs high freeze-thaw stability(> 3 cycles).The whole plant-based walnut-mayonnaise prepared with walnut oil,walnut protein,and rice protein(protein 0.4%,fat 75%,Na Cl 0.1%,wt%)has rheological properties similar to those on the market.It has potential commercial value for its high freeze-thaw stability,low cost,health-related,and environmentally friendly properties at the same time.