title: Effects of acetic acid/acetic anhydride ratios on the properties of corn starch acetates.
abstract: Corn starch was pre-treated with acetic acid and then acetylated by acetic anhydride under microwave irradiation. The effects of molar ratios of these two reagents on the acetylation of starch were investigated. Starch acetate with a high degree of substitution (DS, 2.93) was obtained at a molar ratio (acetic acid/acetic anhydride) of 1:1. However, the DS should tend to decrease with a change of this ratio. The FT-IR analysis indicated characteristic absorption peaks, with increasing DS materialised by an increase of the carbonyl CO group and a decrease of the hydroxyl O-H group, at about 1750cm(-1) and 3450cm(-1), respectively. The X-ray diffraction patterns of acetylated starch showed an amorphous structure. Degree of crystallinity, surface morphology, water solubility and water absorption index of corn starch were also affected by the changes in reagent ratios. The glass transition (Tg) and melting (Tm) temperatures of acetylated starches also decreased after acetylation.
authors.affiliation: Huazhong Agricultural University, College of Food Sciences and Technology, 430070 Wuhan, Hubei, PR China.
authors.forename: Cherif Ibrahima Khalil
authors.initials: CI
authors.lastname: Diop
authors.affiliation: Huazhong Agricultural University, College of Food Sciences and Technology, 430070 Wuhan, Hubei, PR China.
authors.forename: Hai Long
authors.initials: HL
authors.lastname: Li
authors.affiliation: Huazhong Agricultural University, College of Food Sciences and Technology, 430070 Wuhan, Hubei, PR China. Electronic address: bijunxie@sina.com.
authors.forename: Bi Jun
authors.initials: BJ
authors.lastname: Xie
authors.affiliation: Guelph Food Research Center, Agriculture and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario, Canada N1G 5C9.
authors.forename: John
authors.initials: J
authors.lastname: Shi
keywords: Acetic acid/acetic anhydride ratios; Acetylation; Corn starch; Degree of substitution; Microwave heating; Physical properties