Preparation, Property And Characterization Of Acetylated Amylose Corn Starch

The amylose corn starch has unique properties. In order to improve the property of amylose corn starch and enlarge its application field, the amylose corn starch was modified by acetic anhydride.The preparation of the amylose corn starch was studied by using the high amylose corn starch as material, the sodium hydroxide as dispersant agent, the Butyl alcohol and the isoamylol as complex agent and the acetic anhydride as acylate agent in this paper. Study the amylose corn starch yield coefficient and the substitution degree of acetylated amylose corn starch effect of factors such as sodium hydroxide solution concentration, standing time, amount of butyl alcohol (the volume ratio of butyl alcohol to isoamylol), reaction temperature, reaction time, amount of acetic anhydride (the percentage of the mass ratio of acetic anhydride to the dry amylose corn starch) and pH. The optimum conditions for preparing amylose corn starch and acetylated amylose corn starch were obtained by Design-Expert software on the bases of single factor. The amylose corn starch content confirmed by compared with the blue value of standard sample and product. The substitution degree of acetylated amylose corn starch was determined by the saponification method. The results showed that the best technology conditions for preparing the amylose corn starch were:sodium hydroxide solution concentration 0.5mol/L, standing time 24h and amount of butyl alcohol (the volume ratio of butyl alcohol to isoamylol) 82%. And the best technology conditions for preparing the acetylated amylose corn starch were: reaction temperature 29℃, reaction time 2.Oh, amount of acetic anhydride (the percentage of the mass ratio of acetic anhydride to the dry amylose corn starch) 8.7%, pH 8.5.The acid and alkali resistance, cold and hot viscosity stability, blue value of amylose corn starch were improved but the retrogradation, freeze-thaw stability and swelling power were decreased compared with the high amylose corn starch. The acid and alkali resistance, cold and hot viscosity stability, retrogradation and swelling power of amylose corn starch were improved but the blue value and freeze-thaw stability were decreased after the amylose corn starch was modified by the acetylation.The granular structure, thermal property, microcrystalline structure and particle morphology of the high amylose corn starch, amylopectin corn starch, amylose corn starch and acetylated amylose corn starch were characterized by the infrared spectrogram, differential scanning calorimetry, X-ray diffraction and polarizing microscope. The results showed that:The absorption peak of acetylated amylose corn starch at wave number 1730 cm-1 was carbonyl groups. It proved that the carbonyl group was introduced into the molecules of the acetylated amylose corn starch owing to the acetylation. The onset temperature, peak temperature, and end temperature of amylose corn starch were improved but the melting enthalpy was decreased compared with the high amylose corn starch. After the amylose corn starch was acetylated, the onset temperature, peak temperature, and end temperature of acetylated amylose corn starch were decreased, but the melting enthalpy of acetylated amylose corn starch was higher than that of amylose corn starch. The crystallinity degree of high amylose corn starch, amylopectin corn starch, amylose corn starch and acetylated amylose corn starch were 19.06%、0%、0%、25.94%. The granular structure of high amylose corn starch was destroyed after separated. The microcrystalline structure of amylose corn starch was changed after the amylose corn starch was modified by the acetylation. The polarization cross of high amylose corn starch was distinctly observed, and the particle morphology shape of high amylose corn starch was ellipsoid. The polarization cross of amylose corn starch and acetylated amylose corn starch was disappeared, and the shape of particle morphology was irregular block.