Studies On The Removal Of Cholesterol From Yolk With β-CD Immobilized Magnetic Materials

Functional magnetic materials were widely used in separating and extracting targets in the field of food, environment, chemistry and other fields due to their beneficial properties: small particle size and quick response under magnetic field. β-CD immobilized magnetic materials were one of the functional magnetic materials which retained the advantages in coating hydrophobic substances and the beneficial properties of magnetic materials. Compared with traditional methods, β-CD immobilized magnetic materials have advantages in cholesterol removal from yolk due to the reason that the functional material was rapid binding with the target molecule and the material could be separated rapidly from the system. Most importantly, β-CD was unlikely remained in the food system thus the applying security of β-CD was improved.In this study, β-CD immobilized magnetic materials were prepared by coating β-CD on the chitosan modified magnetic nanoparticle with cross-linking agent“1, 6-hexamethylene diisocyanate”and catalyst “stannous 2-ethylhexanoate”. Appropriate preparing conditions of the magnetic nanoparticles were studied.The reacting time was 60℃,stirring speed was 700 r/min and the mass ratio of β-CD to Fe₃O₄@chitosan-HMDI was 3:1. The size, morphology and magnetic properties of β-CD immobilized nanoparticles were analyzed. The processes designed in our study to prepare Fe₃O₄@cyclodextrin magnetic materials were simple and efficient. It was found that the average size of nanoparticles was 232 nm and the magnetic materials show sphere morphology with good magnetic properties, dispersity and high stability. Magnetic content of Fe₃O₄@cyclodextrin was about 64.2%.With these chitosan modified nanoparticles grafted with cyclodextrin, process of cholesterol adsorption conducted in standard cholesterol solution was studied. The adsorption process was analyzed using pseudo first order and second order model. Results showed that the adsorption equilibrium was within 45 min at 25℃and pH 3.0, the maximum adsorbing amount was 210 mg/g. The cholesterol adsorption process could be described by pseudo-second order.The application of Fe₃O₄@cyclodextrin magnetic materials in removing cholesterol from yolk was investigated in our study. Several factors such as the amount of magnetic materials added, temperature, dilution fold, pH and enzymatic pretreatment were analyzed. Following were the preferable removal conditions: adsorbing time was remained at 80 min; mixing ratio of yolk and water was 1:10（w/v）; pH of yolk was set to 3.0 and 9.0. At optimized conditions, cholesterol removal efficiency could reach 58% and the conditions were beneficial for further application of yolk.The change of the amount of protein, lecithin and emulsifying properties of yolk were studied after the Fe₃O₄@cyclodextrin magnetic materials removing cholesterol from yolk. Protein loss was about 7.6% and Lecithin loss was about 9.1% when the cholesterol removal efficiency was 42%. Protein structure changes occurred when the cholesterol was removed from yolk and the emulsifying properties of yolk were lowered. Fe₃O₄@cyclodextrin magnetic materials have good recycling properties as the cholesterol adsorption amount of Fe₃O₄@cyclodextrin magnetic materials remained above 200 mg/g after repeating adsorption-elution process 15 times and the recovery of Fe₃O₄@cyclodextrin magnetic materials can remain 95% after 15 repeated times.