| The preparation of whey protein isolate is mature and it has high nutritional value,which can be a multifunctional component of gelling,foaming and emulsifying properties.It can be used as a good emulsifier,but its thermal sensitivity limits the application in the food field.Heating and pH adjustment are common processing methods in food processing.Through acid and heat treatment,food protein can be formed into nano-fiber,which provides new ideas for the development of its functional characteristics.At present,conditions for fibrils of preparation are relatively mature.Pickering emulsion has some advantages including less emulsifier,no pollution and high stability.The high bioactivity and low bioavailability of natural active ingredients limit their effective supplement in diet.Pickering emulsion is expected to be used for the encapsulation,protection and delivery of such hydrophobic functional active ingredients.However,there are still some problems to be solved:1.The formation mechanism of fibril aggregates and the structural regulation and control of fibril aggregates under different conditions should be solved and how to investigate the emulsification changes.2.Optimization of the fibril stabilized-Pickering emulsion which can be used as a delivery system for natural hydrophobic molecules.Whey protein isolate can be used as raw material in this study.Nanofibrils were formed by heating.As a stabilizer,they can stabilize Pickering emulsion.To research the formation and stability of Pickering emulsion loaded with nobiletin.To provide theoretical data of reference for the construction and the improvement of bioavailability of Pickering Emulsion late-loaded nobiletin.The research results are as follows:1.The formation of the Self-assembly and regulation of structure in whey protein nanofibrilsThe WPI fibril was formed by heat and acid treatment.The process was happened with denaturation of protein and hydrocortisone into peptide.The structure of the fibril was affected by pH.When pH is 5,aggregation occurs due to the proximity to the isoelectric point,and it is speculated that such aggregation is caused by a single fibril entanglement.The concentration of WPI fibrils had no effect on its morphology.However,there was a tangle when the concentration increases to 0.4wt%in solution.2.Effect of pH and fiber concentration on the emulsifying properties of whey protein isolate nanofibrilsThe fibrils have good emulsifying properties.WPI fibrils with different pH and concentration have important effects on the emulsifying properties of fibrils.Stable emulsion can be formed with fibrils under different pH(2-7)and different concentration(0.1%-1.25%).When pH is adjusted to the isoelectric point,emulsifying properties of WPI fibril are more extensive,and the intermolecular force is weakened,which reduces the rate of fibril adsorption to the interface.When the concentration is low(less than 0.5%),the nanofibril is not enough to cover the entire interface.When the concentration is too high,the depletion between the unadsorbed fibril will lead to flocculation of the emulsion.3.Optimization of preparation conditions and stability study of Pickering emulsion stabilized by whey protein isolate nanofibrilThe fibril forms a stable Pickering emulsion at a very low concentration(0.1%fibril,0.7 oil fraction or 0.05%fibril,0.5oil fraction).Stable full emulsion can be showed with high oil phase and low fibril concentration(0.7oil,0.5%fibril).After long-term storage for 28 days,the whey protein isolate nanofiber-stabilized Pickering emulsion still has high stability.Under pH and salt ion conditions,the whey protein isolate nanofibers were stable.After loading the nobiletin,the whey protein nanofiber-stabilized Pickering emulsion is still relatively stable,and the fiber is stable at the oil-water interface to prevent the crystallization of the nobiletin.The oil droplet can prevent the crystallization of nobiletin. |
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