Physico-chemical properties of acetylated starches from Indian black gram (Phaseolus mungo L.) cultivars.

Starches separated from three black gram cultivars were modified by acetylation and compared to their native starches. Acetylation was carried out by treating starches with 0.04 and 0.08 g of acetic anhydride/g of starch dry weight basis (db) at 25 °C. The extent of acetylation increased proportionally with the concentration of acetic anhydride used. Retrogradation of acetylated starch pastes decreased significantly (p ≤ 0.05) as revealed by significant decrease in syneresis, increased freeze thaw stability and increased light transmittance. The pasting curves of 10.7 % starch slurries showed that acetylation decreased the setback viscosity values by 51.2-82.8 % and pasting temperature by 3.1-5.6 °C than respective native starches. Differential scanning calorimetry observations also revealed significant decrease in gelatinisation temperature of acetylated starches than native starches. Hardness and adhesiveness of starch gels varied between 10.3 and 32.6 g and 4.6-82.3gs, respectively which were significantly lower than corresponding native starch gels.