Abstract

Butyrylated arenga starches (BAS) with different degree of substitution (DS 0.074, DS 0.151, DS 0.226) were synthesized by the reaction of arenga starch with butyric anhydride under varying pH and butyric anhydride concentration. The products were characterized for resistant starch (RS), chemical structure of the RS by nuclear magnetic resonance (NMR) spectroscopy and functional properties including water and oil holding capacity (WHC and OHC), bile acid/salts and cholesterol binding. The results indicated that RS increased with increase in the DS of BAS. Analysis of ¹H NMR spectra of RS from BAS revealed the presence of methylene (CH₂) and methyl (CH₃) protons, while the ¹³C NMR spectra gave the signals of methylene, methyl and carbonyl carbon of butyryl groups. Compared to the ¹³C NMR spectrum of the native starch, the modified starches gave additional signals broadening of the C1 and C6 signals. Those results further suggested that the butyryl groups were substituted at the C2 and C6 positions. The WHC and OHC of RS from BAS increased with increase in the DS, indicating that butyrylation increased both hydrophilicity and hydrophobicity of the starches. The bile acid/salts of RS from BAS increased with the increase of DS and the total cholesterol decreased with the increasing DS.

Key words: Resistant starch, butyrylated arenga starch, degree of substitution.