Preparation And Application Of Soybean Separation Protein/Chitosan Hydrochloride Complex

The protein and polysaccharide complex system is a research hotspot in the fields of medicine,food and cosmetics.The protein-polysaccharide complexes with unique functional characteristics can be prepared by controlling the processing conditions.The use of such complexes as carriers of bioactive compounds can not only improve their water solubility and the environmental sensitivity,covering bad flavor,etc.,but also achieve the accurate release of the bioactive compounds and improve their bioavailability during digestion.In this thesis,the interaction between soy separation protein(SPI)and chitose hydrochloride complex(CHC)under different p H,SPI/CHC ratio and particle concentration has been investigated,and the application prospects of SPI/CHC complex in the stabilization of Pickering emulsion and encapsulation of bioactive compounds have been explored.The results obtained are as follows:(1)The existence state of SPI and CHC and their interaction under different p H conditions were studied.It is found that the CHC/SPI complex system forms soluble complex between p H3 and 6.5,and condenses near the isoelectric point of the system(p H 7.8),at which time CHC/SPI binds most tightly and forms insoluble complex.FITR,DSC and SEM analysis indicated that the gel network structure was formed between CHC/SPI complexes through electrostatic interaction.(2)Pickering emulsion with CHC/SPI soluble complex was prepared by adjusting p H,CHC/SPI mass ratio,total concentration of CHC/SPI and oil ratio,and the microstructure,stability and rheological properties of the emulsion were studied.It is found that CHC/SPI soluble complex particles formed at the mass ratio of CHC/SPI 1:1,p H 4 and particle concentration of 2% could stabilize Pickering emulsions with an oil ratio of up to 0.8,while the particle size was the smallest when the oil ratio was 0.6.The emulsion can be stored for more than 30 days at room temperature without delamination or demulsification.The emulsion droplets are round in shape and closely connected with each other,squeezing each other.They have high apparent viscosity and strong gel properties and can withstand external forces.During the storage period,the emulsion forms a hard shell due to the CHC/SPI complex particles,which protects lipids from oxidation to a certain extent.(3)Citrus essential oil emulsion(CEOP)was prepared using Pickering emulsion stabilized by CHC/SPI complex.The results of antibacterial and antioxidant assays showed that CEOP could effectively inhibit the growth of S.aureus and E.coli.The antioxidant activity was dependent on the content of essential oils in CEOP.The results showed that CEOP emulsion diluent(CEO concentration 4500μL/L)not only improved the water solubility of essential oil,but also reduced the Browning rate of fresh cut apple.(4)Structural characteristics and in vitro digestibility of rutin microcapsules embedded in CHC/SPI composite condensate(SC)were investigated.CHC/SPI condensate-RUT microcapsules were prepared under the conditions: CHC/SPI ratio 1:8,the total concentration2%,and p H 6,RUT concentration 200 mg/L.The encapsulation rate and loading capacity of the microcapsules were 90.34% and 5.1%,respectively.The microcapsules showed gel network structure with strong thermal stability,and the system was stable and uniform after 12 days of storage.In the process of in vitro digestion,the release rate of SCR microcapsules in gastric juice was 16.97%,and the release rate in intestinal juice was 76.53%,thus the slow release of RUT in the digestive process was achieved.In addition,the digestive products were found to possess good antioxidant activity.