Study On The Encapsulation Of Bioactive Materials Based On Whey Protein Isolate-sodium Alginate Complex Carriers

Bioactive components,including vitamins,phenolic compounds and so on,can adjust the physiological function of human body and prevent or delay the onset of chronic diseases.However,many bioactive components have poor water solubility or stability and are highly susceptible to degradation during food processing and storage process by light,oxygen,temperature,pH and other environmental factors,therefore losing their activity and limiting practical application in food industry.These bioactive components can be encapsulated and protected by edible carriers to overcome the limitations.It is inevitable to design a carrier that can contain multiple bioactive components simultaneously with the development of a variety of healthy functional foods.Protein has many functional properties such as emulsification,gel-forming,ligand binding,polysaccharide complexation and so on.The combination of protein and polysaccharide has been found to improve the stability and function properties of protein.Whey protein isolate?WPI?was selected as the model protein in this thesis,using its ligand binding,emulsification,the complexation characteristics with polysaccharide,and gel-forming characteristics of polysaccharide gel assembly again,to explore the co-encapsulation effect of?-tocopherol/resveratrol,propolis and?-tocopherol in the assemblies.We also studied the influence of the stability of bioactive components and discussing the possibility of reassembly based on single protein emulsion as a carrier to co-encapsulate bioactive components.The main content of this article could be divided into two parts:?1?The encapsulation of?-tocopherol/resveratrol in emulsion-filled gel beads based on WPI and Ca-alginate:Ca²⁺-induced emulsion-filled gel beads were prepared by the combination of heat-denatured WPI's emulsification and alginate's gelation at various contents of WPI and oil for co-encapsulation of resveratrol and?-tocopherol.Influence of the content of WPI and sunflower oil in the emulsion-filled gel beads on encapsulation efficiency,stability during storage and simulate gastro-intestinal digestion,and the changes of gel beads themselves were also studied.High efficiency for the co-encapsulation of resveratrol and?-tocopherol was achieved for the emulsion-filled gel beads containing 1%WPI and 1%-4%oil.Encapsulation efficiency of resveratrol gradually increased as the protein content increased from 0.1%to 1%.WPI content was more important than the content of oil for the protection of resveratrol while the content of oil was more important for the encapsulation and protection of?-tocopherol during storage.Resveratrol remained 73%after releasing from the emulsion-filled gel beads containing 1%WPI and 1%-2%oil for 6 h.The release of?-tocopherol was less than 20%while resveratrol was rapidly released during simulate gastric fluid digestion.?2?The encapsulation of propolis or?-tocopherol in complex emulsion based on WPI and sodium alginate:The contents of total phenol and total flavone in ethanol extracts of Brazilian propolis were 126.94 mg/g and 54.15 mg/g propolis,respectively.Propolis-WPI and propolis-WPI-sodium alginate particals were prepared and the solubility of propolis in water had been significantly increased.In three antioxidant methods,different results were found.For the ABTS⁺?radical scavenging ability,the propolis-WPI nanoparticles was stronger than propolis in ethanol.For DPPH?radical scavenging ability,the ability was unchanged.For FRAP method,the reducing power was lower than propolis in ethanol.The partical size and absolute value of?-potential of propolis-WPI solution were increased after adding sodium alginate.When the concentration of alginate was 1 or 2 mg/mL adding to the propolis-WPI solution,the storage stability was increased.According to the anti-oxidation property of propolis,propolis was added to the emulsion containing?-tocopherol to investigate whether propolis can retard the degradation of?-tocopherol or not.The influence of propolis'addition on emulsion particle size and?-potential were characterized.The retention of the main components of propolis and?-tocopherol during storage period and the effect of the addition of propolis on the digestive stability of propolis in emulsion were also studied.The addition of propolis and and sodium alginate solution had no significant effect on the initial particle size compared to blank emulsion.Whereas the?-potential value of emulsion increased significantly after adding sodium alginate.However,the?-potential value and size of all kinds of emulsions had no obvious change at 25?and 45?after 30 days,which means all of them were stable during storage.From the results of 45?storage experiment,we found that adding propolis can obviously improve the retention of?-tocopherol after storage from 76.35%to 91.52%,further ups to 95.40%once adding sodium alginate solution.And the addition of propolis can also significantly improve the stability of artificial?-tocopherol in simulate intestinal fluid digestion.