Study On The Location And Encapsulation Of Bioactive Components In O/W Emulsion Stabilized By Whey Protein Isolate

Whey protein isolate?WPI?has been suggested to be used as an edible carrier in the food industry because of its high nutritional value and multiple functional properties.O/W emulsions stabilized by WPI have been widely used as effective carriers for hydrophobic bioactive components to improve the water solubility,environmental sensitivity and bioavailability.However,the traditional protein-stabilized O/W emulsion has large specific surface area,thin interface protein layer,and low internal oxidation stability of the oil phase.In addition,it was only used as an encapsulated carrier for a single hydrophobic bioactive component.Based on multiple functional properties of proteins including emulsification,aggregation and binding of low-molecular-weight ligands,antioxidants can co-adsorb to the oil-water interface layer and portion in aqueous phase to improve the oxidative stability of the emulsion,and it is possible for co-encapsulation of multiple bioactive components with different solubility characteristics in protein-stabilized O/W emulsion.In this thesis,heat-denatured whey protein isolate?hWPI?was chosen as an emulsifier model to prepare O/W emulsion for encapsulation of the amphiphilic resveratrol.The encapsulation,localization of resveratrol and the oxidative stability of the emulsion was studied.The results will provide theoretical guidance for the design and development of co-encapsulation carrier by the protein-stabilized O/W emulsion with high oxidative stability.The main contents and results of this thesis were drawn as follows:1.The sunflower oil emulsions stabilized by hWPI were prepared.The influence of Ca²⁺and gum Arabic on emulsion structure,encapsulation and partition of resveratrol,and lipid oxidation stability were studied.The results showed that high concentration of Ca²⁺or gum Arabic could significantly increase the protein content at the oil-water interface of hWPI emulsion.Resveratrol transferred to more hydrophobic environment with addition of Ca²⁺and gum Arabic.The oxidative stability of oil in hWPI emulsions were improved by adding Ca²⁺while high concentration of gum Arabic reduced the oxidative stability slightly.It significantly delayed the oxidation of oil with encapsulation of resveratrol in emulsions.It could achieve co-encapsulation of resveratrol and vitamin D₃ in O/W emulsion stabilized by hWPI-Ca²⁺-gum Arabic,since had high encapsulation efficiency and did not cause side effect each other.2.The sunflower oil,origanum essential oil and peppermint essential oil were chosen as internal oil phase with different polarity and resveratrol solvency,and gum Arabic as a polysaccharide model to prepare hWPI emulsions.The influence of oil type and gum Arabic on emulsion structure,total encapsulation efficiency and partition of resveratrol in emulsions were studied.Sunflower oil emulsion had the highest interfacial protein content comparing to essential oil emulsions stabilized by hWPI.The total encapsulation efficiency of resveratrol in different hWPI emulsions were as follows:peppermint essential oil emulsion?⁹8%?>sunflower oil emulsion?⁶6%?>origanum essential oil emulsion?⁴8%?.In peppermint essential oil emulsion,resveratrol was mainly encapsulated in internal oil phase of emulsified oil droplet,and interfacial protein content did not significantly affect content of resveratrol in emulsified oil droplet and total encapsulation efficiency in emulsion.In sunflower oil and origanum essential oil emulsions,resveratrol were mainly encapsulated on oil-water interface layer of the emulsified oil droplets,and the content of resveratrol on oil-water interface layer increased with increase of interface protein content.Gum Arabic improved the interfacial protein content of all emulsions and the encapsulation efficiency of resveratrol on the oil-water interface layer of sunflower oil and origanum essential oil emulsions.Resveratrol had high storage stability in all emulsions system,and it was the highest in the peppermint oil emulsion.3.The emulsions stabilized by hWPI-polysaccharide for co-encapsulation of resveratrol and fish oil were prepared,to study the influence of concentration,type and order of addition of polysaccharide on emulsion structure,encapsulation efficiency and stability of active ingredients.Gum Arabic's concentration and order of addition had less influence on the emulsion when the concentration?0.50%.The size and absolute potential of the emulsions increased significantly with the increase of concentration of pectin,and the influence were similar for adding pectin before and after emulsifying when the concentration?0.20%.The emulsions had larger size for adding high concentration of polysaccharide after emulsifying than before while emulsions stability decreased by adding pectin after emulsifying.Low concentration of polysaccharide did not significantly affect the encapsulation efficiency and stability of resveratrol.The total encapsulation efficiency and content in the emulsified oil droplets of resveratrol increased with the polysaccharide's concentration?0.50%,and pectin was more effective than gum Arabic,but the stability of resveratrol were reduced.The encapsulation of resveratrol did not affect by order of addition of polysaccharide.Polysaccharide had no significant influence on the encapsulation efficiency of EPA and DHA.Adding low concentration of polysaccharide before emulsifying could slightly improve the stability of EPA and DHA but reduced at high concentration,and the stability of EPA and DHA did not depend on the type of polysaccharide.Emulsions stabilized by hWPI could significantly improve the oxidative stability of fish oil,and content of oxidation products decreased by adding 0.05%gum Arabic before emulsifying but increased when the concentration of gum Arabic?0.50%.The addition of pectin before emulsifying could improve the oxidative stability of fish oil and it was independent of concentration.It had no significant effect on the oxidation stability of fish oil by adding gum Arabic after emulsifying.Encapsulation of resveratrol in hWPI-stabilized fish oil emulsions could improve the storage stability of EPA and DHA and the oxidation stability of fish oil.