Preparation Of Whey Protein-maltodextrin Microcapsules And Their Encapsulation And Protection Of Bioactive Compounds

Bioactive compounds such as functional oils and antioxidants have various health benefits.The co-fortification of different bioactive compounds in food can not only improve the efficiency of resource utilization,but also improve the added value of products.However,many bioactive compounds have poor water solubility and are highly sensitive to environmental factors such as light,heat,and oxygen.They are prone to degrade during processing and storage,resulting in reduced or lost biological activity.Moreover,bioactive compounds with different physicochemical properties are difficult to be directly stabilized in food systems.Microcapsules prepared by spray drying have been widely used in the encapsulation and protection of different bioactive compounds.But most researchers focus on the microencapsulation of a single bioactive compound,and their loadings are relatively low.In addition,the study on the co-encapsulation of multiple bioactive compounds with different physicochemical properties is relatively rare.Whey protein isolate(WPI)has high nutritional value and various functional properties including emulsification and the complexation characteristics with polysaccharides.Heat denaturation can expose more hydrophobic residues and improve its emulsifying properties.The combination of various wall materials can improve the encapsulation efficiency of microcapsules.The addition of maltodextrin(MD)can reduce the viscosity of droplets and improve the retention and stability of microcapsules.In this study,microcapsules using heat-denatured/native whey protein isolate(h WPI/WPI)and maltodextrin(MD)mixtures as wall materials were produced by spray drying to achieve the high load of vitamin E and the co-encapsulation of fish oil and curcumin.The results will provide theoretical guidance for the co-encapsulation of different bioactive compounds based on spray drying.The main contents and results of this study are as follows:1.Construction of microcapsules with high encapsulation efficiency.Using mediumchain triglyceride as the oil phase,and effects of heat denaturation temperature,type of polysaccharide and maltodextrin content on the properties of emulsions and microcapsules were explored.It was found that when the heat denaturation temperature was 85℃,the surface oil content of microcapsules was lower,the encapsulation efficiency was higher,and the solubility was good.The addition of maltodextrin can further reduce the surface oil content.When the maltodextrin content was 5%,the surface oil content of microcapsules was0.62%,which can meet the demand of food industry.On this basis,the effect of h WPI and WPI ratio on structure,physicochemical properties and stability of initial,reconstituted emulsions and microcapsules were further explored.All emulsions were stable and their viscosity was lower than 0.3 Pa·s,which can ensure good atomization.Microcapsules with higher h WPI content(3%-7%)showed lower surface oil content and higher encapsulation efficiency,leading to their better storage stability.And wall materials consisting of 5% h WPI,5% WPI and 5% MD had the highest encapsulation efficiency(97.70%)for 10% MCT,which may be related to the interfacial protein content.Moreover,the microcapsules with different h WPI and WPI ratios had good solubility,low moisture content and water activity,and their hygroscopicity was relatively low.It was conducive to their application in the food industry.2.Preparation and characterization of microcapsules with high vitamin E content.The lipid-soluble bioactive compound vitamin E was added to medium-chain triglycerides to prepare vitamin E microcapsules,and the effect of vitamin E content on the properties of emulsions and microcapsules was explored.It was found that emulsions with different vitamin E contents were stable.With the increase of vitamin E content,the surface oil content of the microcapsules increased,while the encapsulation efficiency and solubility decreased.Microcapsules with different vitamin E contents had good thermal stability,their moisture content was below 4% and water activity was below 0.3.The increase of vitamin E content had no significant effect on its retention.After storage at 45℃ for 35 days,the microcapsules with 20% vitamin E can retain ～68% vitamin E.3.Preparation and characterization of fish oil and curcumin co-encapsulated microcapsules.Using fish oil as the oil phase,the amphiphilic bioactive compound curcumin was added to h WPI to prepare fish oil and curcumin co-encapsulated microcapsules,and the effect of curcumin content on the properties of emulsions and microcapsules was explored.It was found that increasing curcumin content had no significant effect on size distribution of the initial emulsions and ζ-potential of the emulsions.The obtained emulsions were stable.There was no significant difference in the surface oil content,encapsulation efficiency,moisture content,water activity,flowability and curcumin retention of microcapsules with different curcumin contents,but the increase of curcumin content could significantly improve the solubility,oxidative stability and retention of EPA and DHA of microcapsules.The microcapsules with 0.80% curcumin can still retain 81% curcumin,39% EPA and 39% DHA after storage at 45℃ for 35 days.The obtained microcapsules had good thermal stability and oxidative stability,and can provide effective protection for bioactive compounds.