Effect of dual modification of acid-ethanol treatment and acetylation on physicochemical properties of corn starches and starch films

• Main Authors: Fung-Ming Lin, 林芳民
• Other Authors: Yung-Ho Chang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/48828973838862635670

碩士 === 靜宜大學 === 食品營養研究所 === 98 === Corn starches (Waxy corn, Normal corn and Hylon VII) with different amylose contents were used to prepare starches with different molecular sizes by acid-ethanol treatment (AET), then, the modified starch was treated by acetylation. The physicochemical properties of native and modified starches and starch films made from them were determined for elucidating of the dual modification on starch. Results showed that the recovery of corn starches was higher than 96% after AET. The average molecular weight of corn starches decreased with increasing extent of AET. The degree of substitution (DS) of all acetylated starches increased with increasing concentration of acetic anhydride. The DS of normal corn and Hylon VII starches decreased with increasing extent of AET. However, the DS of waxy corn showed a reverse tendency. The gelatinization onset temperature, peak temperature and conclusion temperature of corn starches decreased with increasing concentration of acetic anhydride. Besides, the gelatinization onset temperature decreased with increasing extent of AET. The light transmittance of corn starch pastes increased with increasing extent of AET and acetylation. However, the light transmittance of starch pastes after refrigerated storage decreased with increasing duration of storage, this was resulted from retrogradation of the starches molecular. After AET, gel consistence of starch pastes obviously increased with increasing duration of AET. Gel consistence of starch pastes increased with increasing extent of acetylation. However, gel consistence of starch pastes made from native waxy corn and normal corn starch after acetylation was lower than the starch pastes made from their native counter parts. Besides, the gel consistence decreased with increasing extent of acetylation, this could be due to the increase in viscosity of starch after acetylation. Films of corn starch after dual modification had high transparency. Furthermore, the transparency of films increased with increasing extent of AET and acetylation. Films from native starch had higher tensile strength, but decreased after AET and acetylation. The tensile strength of starch films decreased with increasing extent of AET and acetylation. Among the starches, films from Hylon VII starch had the highest tensile strength. Corn starch films had higher elongation after AET and acetylation, and elongation of starch films increased with increasing extent of AET and acetylation. In addition, Hylon VII starch films had the highest elongation in the same conditions of dual modification. Films from corn starch after dual modification provided with high water vapor permeation (WVP), and WVP increased with increasing AET duration and degree of acetylation.