Production of RS4 from rice by acetylation: Physico-chemical, thermal, and structural characterization.

The SR-1, SR-2, Jhelum, and Pusa rice starches were extracted by the alkaline method and acetylated by using acetic anhydride to make modified food starches with high contents of type 4 resistant starch (RS4). The results revealed 6-10-fold increase in the RS4 content of rice starches via acetylation. The acetyl % and degree of substitution values (DS) of rice starches ranged from 1.83 to 2.31, and 0.05 to 0.10, respectively. The introduction of acetyl groups in starch chains was confirmed via Fourier transform infrared spectroscopy (FTIR). Acetylation was found to increase water absorption capacity, oil absorption capacity, bile-acid binding, swelling power, solubility index, light transmittance (%), and freeze-thaw stability, whereas amylose content, syneresis, pasting parameters, and thermal properties decreased with acetylation. The SEM micrographs of the acetylated rice starch revealed the presence of polyhedral granules with rough surfaces. Also fissures and deformed depressed zones were observed in some granules. [ABSTRACT FROM AUTHOR]