Abstract:

In this study, the process for preparing acetylated acid modified waxy corn starch from waxy corn starch by acetic anhydride acetylation under the catalysis of sodium hydroxide and subsequent hydrochloric acid hydrolysis, in which anhydrous sodium sulfate was first added to starch milk as a swelling inhibitor, was studied. Meanwhile, the modified starch prepared was functionally characterized. Waxy corn starch had been modified by hydrochloric acid was acetylated by acetic anhydride to explore the effects of the acetylation reaction conditions, including temperature, time, pH, acetic anhydride loading, and anhydrous sodium sulfate loading, on starch substitute degree. Additionally, the effect of the sequential order of acetylation and acidic hydrolysis on starch substitute degree and fluidity was evaluated when the reaction conditions of acidic hydrolysis and acetylation were both kept unchanged, and the results showed no effect. The above reaction conditions were all found to affect the preparation of acetylated acid modified waxy corn starch. The optimum conditions for the acetylation of hydrochloric acidmodified waxy corn starch with acetic anhydride were determined as follows: reaction at 25 ℃, pH 8.5 for 50 min under the catalysis of 1.5% anhydrous sodium sulfate. After the optimized acetylation, hydrochloric acid-modified waxy corn starch showed an increase in both transparency and freeze-thaw stability, which was positively correlated with substitute degree. Starch retrogradation, however, was not affected by acetylation.

Key words: waxy corn starch, acetylation, acid hydrolysis, preparation, property