Design Of Whey Protein Isolate/oxidized Starch Complexed Particles And Regulation Of Rheology And Digestibility Of Pickering Emulsion

With the global aging society,it is a new challenge for modern nutritious health food industry to creating personalized food for the elderly with dysphagia and glucose metabolism disorder.Elderly liquid nutrition formula food is a complexed emulsion system composed of macronutrients such as carbohydrates,proteins,lipids and suitable kinds of vitamins and minerals.It is an effective way to realize the personalized creation of elderly liquid food by controlling the distribution of emulsion components and the structure of O/W and W/W interfacial film for synergistic regulation of emulsion stability,rheological properties and digestibility.Therefore,based on the composition of elderly liquid nutrition formula food and the characteristics of colloidal particles suitable for stabilizing O/W and W/W Pickering emulsion interface,the article proposes to control the molecular interaction between whey protein isolate and oxidized starch to obtain complexed micro/nano colloidal particles with different sizes,favourable interface properties and digestibility,and to design Pickering emulsions with different interface properties.To reveal the regulation mechanism of its stability,rheological properties and digestibility,and on this basis to construct elderly liquid nutrition formula food for those with dysphagia and glucose metabolism disorder.Based on the characteristics of Pickering colloidal particles which are suitable for stabilizing oil-water and water-water interfaces,corn starch was oxidized to introduce negatively charged groups for starch molecules,and then combined with whey protein isolates obtained under different heating conditions to prepare whey protein isolate/oxidized starch complexed micro/nano colloidal particles.The electrostatic and hydrogen bonding interaction between whey protein isolate and oxidized starch was regulated by changing the mass ratio between whey protein isolate and oxidized starch,p H and the amount of cross-linking agent.It was found that the complexed colloidal particles,which are suitable for stabilizing O/W Pickering emulsions,with particle size of 373.53±4.32 nm,Zeta-potential of 8.92 m V,interfacial contact angle of 90.84°,the interfacial tension value of 6.26 m N/m and predicted glycemic index（p GI）of 64.14±0.47 could be obtained when the mass ratio of whey protein isolate,oxidized starch and cross-linking agent was 7:1:0.2 and the p H was 3.5.And for the complexed colloidal particles which are suitable for stabilizing W/W Pickering emulsions,with the particle size of 1228.5±4.95 nm,the potential of-9.62 m V,the contact angles with yam starch and guar gum were 57.64°and 62.86°,and p GI of 50.34±0.22 were obtained when the mass ratio of whey protein isolate heated at 110℃for 20 min,oxidized starch and cross-linking agent was 1:1:1 and the p H was 3.5.Using the obtained complexed micro/nano colloidal particles as interfacial stable particles,O/W and W/W Pickering emulsions with satisfactory stability were constructed by high pressure homogenization/high-speed shear.It was found that both Pickering emulsions were stable through the adsorption of complexed micro/nano colloidal particles on the interface and the formation of interface film through the investigation by laser confocal microscopy.The rheological and digestible properties of Pickering emulsions can be regulated by optimizing the volume fraction and concentration of dispersed and continuous phase,addition of complexed micro/nano particles with different sizes,homogenization pressure/shear rate and so on.The results indicated that both Pickering emulsions showed the characteristics of shear thinning and gel-state elasticity.With the increase of oil ratio,yam starch and guar gum concentration,complexed colloidal particle content and shear rate/homogenization pressure,the emulsion with higher viscosity,stronger gel structure and more stable can be obtained.The coating ability of olive oil and yam starch in O/W and W/W Pickering emulsion was enhanced by properly increasing the amount of complexed colloid particles and shear rate/homogenization pressure,which showed that the digestion degree of olive oil and the p GI value decreased.The W/W Pickering emulsion showed medium or low GI emulsions.O/W and W/W Pickering emulsion with different rheological and digestibility were compounded to obtained the complexed emulsion.The results showed that the complexed emulsion was a multiphase Pickering emulsion which is co-stabilized by heat-treated whey protein isolate microgel/oxidized starch complexed colloidal particles and O/W Pickering emulsion droplets adsorbed on the two-phase interface to form a stable composite elastic film.By adjusting the water/oil ratio,two-phase concentration and the addition of O/W Pickering emulsion,the viscosity of the composite emulsion at 50 s^-1 was between 134.87～669.46 m Pa.s,and the p GI value was between 52.40～55.58,which was 42.89～46.16%lower than that of gelatinized yam starch.The viscosity of liquid formula food based on the complexed emulsion was between 105.85～605.70 m Pa.s and the p GI value was between 62.69～66.74,which belongs to medium GI food.It could maintain excellent system stability,rheological and digestive properties during the storage period（half a month）,and realize the synergistic regulation of rheological and digestive properties,which was suitable for the elderly with different dysphagia and glucose metabolism disorders.In this paper,by regulating the interaction between whey protein isolate and oxidized starch molecules,the complexed micro/nano colloidal particles with suitable particle size,preferable interfacial and digestible properties and stable different interfaces were selected,and the O/W Pickering emulsion and W/W Pickering emulsion with adjustable rheological and digestibility were constructed.By controlling the emulsion formation conditions,particle size and composition distribution design.The control of rheological properties of the complexed system were regulated,and the coating of oil and starch was achieved synchronously,so that the digestion rate of oil and starch was controlled.The elderly liquid nutrition formula food suitable with different dysphagia and glucose metabolism disorders was obtained,which provides a theoretical basis and a new way for the creation of special diet food for the elderly.