| Immunoglobulin G (IgG) is human body's most remarkable active functional factor and physiological material among bovine colostrums. IgG, the main compositional material of the humoral immune, has the immunologic function when combined with specific antigen. However, IgG is sensitive to heat, acid, alkali and digestive enzymes, leading to the reduction of physiological activity. Nowadays, the prevailing solutions are adding protective agents or encapsulating IgG with different methods to improve protein stability followed by separation and purification.In this study, we optimized the extraction and purification process and studied the physicochemical property of IgG. We improved IgG stability through adding protective agents and encapsulating IgG. We investigated the property of microcapsule by scanning electron microscopy (DSC), infrared spectroscopy (FT-IR), in vitro simulation experiment and rheological technologies. The concrete research contents and results are as follows:IgG, purity over 70%, obtained by degreasing, casein precipitation and multi-step salting. IgG had preferable thermal stability under 60°C, but it would be completely deatured merely by short-term treatment above 80°C. IgG's reaction order of thermal denaturation dynamic equation ws 1.1. IgG had preferable acid and alkali stability when pH value ranged from 5.0 to 10.0. Sucrose, maltose, glycine and galactose could significantly improve IgG stability. The best formula of the compotite protective system were composed of 10 wt % sucrose and glycine, with the ratio of 2:1.Soybean oil and whey were respectively used as oil phase and water phase to fully mixed two phases, when Span and Tween series added by certain ratio of oil to water. W/O bovine colostrums whey emulsion was prepared with 5 wt % arabic gum (GA) and maltodextrin (MD) as wall materials and stabilizers, by the method of ultrasonic emulsification. We further investigated the hydrophile lipophile balance value (HLB), composite emulsifiers, the ratio of oil to water, emulsifier dosages and times of ultrasonic emulsification on the system's stability via relative volume and conductance measurements. The optimal technical parameters were as follows: HLB value 4.8, Span-85 and Tween-60 as composite emulsifier, the water/oil ratio 1:1, ultrasonic emulsification for 12 times under a certain condition. The morphology of W/O emulsion was observed by microscope and the emulsion contains uniform droplets with 2μm average particle size. The W/O Bovine colostrums whey emulsion followed shear-thinning behavior, fitting the model of Herschel-Bulkley. IgG microcapsules were prepared by emulsified/spray drying. We further investigated the the ratio of oil to water and of GA to MD, wall materials dosages and air-in temperature on encapsulation efficiency of microcapsules through orthogonal test. The optimal technical parameters were as follows: the oil/water ratio 3:4, GA/MD ratio 1:2, wall materials addition 5%, air-in temperature 140°C. Fine integrity and 1~5μm average particle size of microcapsules were observed using scanning electron microscopy. Infrared test results showed that microencapsulated IgG, containing all characteristic peaks of polyacrylamide, retained the original structure and nutritional value. Model-fitting was used to study the release kinetics of the microcapsules. The results indicated that the microcapsule release in simulated gastric and intestinal liquids obeyed first-order equation, while zero-order equation was best fitted in PBS. |
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