Producing Of Corn Porous Starch By Enzymatic Hydrolysis And Cross-Linking Modification

Porous starch, a new type of modified starch, has various advantages as a kind of absorbent with high efficiency, innocuity, safety and biodegradability. It can be widely used in many industries, including food, medicine, commodity and agriculture, and is becoming a study hotpot. This paper mainly focused on the production process, characteristics and applications of porous starch and cross-linked porous starch which was made from corn starch.During the production process of porous starch, oil absorption ratio of porous starch and degree of the corn starch hydrolysised were use as the index to evaluate the porous starch. Based on single factors and orthogonal experiment designed, optional conditions of porous starch production were obtained: the ratio of alpha-amylase: glucoamylase is 2:1(w:w), the content of enzymes added is 2.4%, reaction temperature is 50℃, pH is 6.0 and the reaction time is 24h. The oil absorption of porous corn starch is 50.23% and the hydrolysis degree of corn starch is 50.23% under this condition. In order to enhance the porous stach's stability, the porous starch was further modified by being cross-linked with POCl3. Settling volume was used as the index to evaluate the cross-linking degree. Finally, we obtained the best reaction conditions: pH is 11, the starch concentration is 70%, 1% (starch weight) POCl3, reaction temperature is 40℃, and the reaction time is 120 min. The settling volume of the cross-linked porous corn starch obtained under this condition is 1.15ml. The physicial properties of porous corn starch and cross-linked porous corn starch were determined. Compared with the native starch, the penetration and solubility increased, the oil absorption and water absorption ratio were 2.4 times of the native corn starch, the surface area were about 2.5 times of the native corn starch and the pore volume is about 5.5×10-3cc/g. The Brabender viscosimeter analysis indicated that: the gelatinization temperature and the stability were lower after enzyme hydrolysis, but after cross-linking these values of porous starch were heightened. The SEM photographes showed that there were many pores on the surface of the starch granule and the diameters were 0.75μm ~1.5μm. For cross-linked porous corn starch was always used as the adsorption and protection medium. The drug loading properties were studied by use methylene blue as the model drug and the quantity of loaring drug, encapsulate efficiency used as the evaluate index. The quantity of loaring drug can reach 29.5mg/g and the encapsulate efficiency reach 68% after. Putting the dry drug loaded cross-linked porous corn strach in artificial gastric fluid and artificial intestinal fluid, the cross-linked porous corn strach show the markedable sustained release properities compared to the native corn starch.