Characteristics of butyrylated arenga starch prepared at different reaction time and butyric anhydride concentration

Butyrylation of starch leads to products with an increased hydrophobicity. Depending on the degree of substitution (DS), some of the highly hydrophilic hydroxyl groups in the anhydroglucose units of starch are converted to more hydrophobic butyryl groups which change the physical and chemical properties. Arenga starch was reacted with butyric anhydride at 5 - 15% (starch basis, sb) in aqueous slurry for 10 - 60 min. The modified starches were characterized for DS, crystallinity, water and oil holding capacity (WHC and OHC), swelling power and solubility and resistant starch (RS) after hydroxylation with α-amylase and amyloglucosidase. The FTIR results indicated that the modification resulted in the butyryl group incorporation with the starch as shown by absorption of the ester carbonyl group at band 1728 cm^-1. Increasing butyric anhydride concentration (5-15%) resulted in increase in DS (0.057-0.226), however, butyrylation with 5% butyric anhydride for 40 min resulted in the maximal DS. X-ray diffraction revealed that increasing DS was related to decreasing crystallinity. The WHC and OHC of butyrylated arenga starches increased with increasing DS indicating increase in both hydrophilicity and hydrophobicity of the starches. Swelling power increased and solubility decreased with the increasing DS. The RS derived from butyrylated arenga starches tended to increase with the increase of DS. The data obtained in this study indicated the possibility of the application of the butyrylated arenga starch with potential health properties in food product development.