Effect of pepsin and SO2 treatments on the yield, physicochemical, morphological, and functional properties of pearl millet starch

Abstract

Influence of enzymatic and SO2 treatments on the yield, physicochemical, functional, morphological, and colour properties of starches isolated from pearl millet (Ashana and Demby cultivars) was studied. The treatment conditions were; control (steeping for 24 h with 0.2% SO2), B (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH, 4.5), S (steeping for 7 h with 3 h in distilled water and 4 h in 0.2% SO2), BE (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH (4–4.5) + 250 mg pepsin) and BES (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH, 4.5, + 250 mg pepsin + 0.2% SO2). The result showed that starch yield from the treatment BE, BES and S was significantly (p ≤ 0.05) higher than that of B and control treatments in both cultivars. From the micrographs studies, the hydrolytic effect of pepsin on protein matrix attached to the starch could be observed as holes created on the surface of starch granules. All treatments significantly (p ≤ 0.05) affected the amylose content and pH value of both starches, while the falling number and acidity were not affected (p ≥ 0.05) by these treatments compared to controls. Water absorption capacity and fat absorption capacity reduced significantly in all treated starches from the two pearl millet cultivars, while viscosity increased following treatments in both cultivars except treatment S (p ≤ 0.01). In conclusion, functional properties and yield of starch from both millet cultivars were improved by using a combination of enzyme and SO2 during wet milling process.