Effects of Annealing and Heat Moisture Treatments on the Physicochemical Properties of White Sorghum (Sorghum bicolor) Starch

Abstract

The effects of annealing and heat-moisture treatment on the digestibility and physicochemical properties of white sorghum (sorghum bicolor) starch were studied. The native sorghum starch isolated from the sorghum grains was modified physically by heat – moisture treatment at 100oC, 16 hour at 25% moisture level; and annealed at 50oC for 24 hours. The physicochemical properties such as swelling, solubility, morphology, etc. of the native sorghum starch (NSS), heat moisture treated sorghum starch (HSS) and annealed sorghum starch (ASS) were studied. Pasting property of the starches was determined with the aid of Rapid Visco Analyzer (RVA), while their resistant, total and digestible starch were also determined. The amylose content (27.01%) of the NSS decreased after modification to 26.90% (HSS) and 26.10% (ASS) respectively. The starch solubility and swelling power increased in the temperature range, 50 – 90oC, with the native starch having the highest values. Also, the water absorption capacity of the starches reduced from 1.47gg-1 in NSS to 1.26gg-1(ASS) and 0.867gg-1 (HSS). The total starch reduces from 22.83% in NSS to 19.60 and 20.65% in ASS and HSS respectively. Annealing reduces the resistance starch of the NSS from 19.33% to 7.45% while heat moisture treatment increased  it from 19.33 to 19.97%. Keywords:  Sorghum, Annealing, Heat moisture treatment, Digestibility.