Extraction of starch from hulled and hull-less barley with papain and aqueous sodium hydroxide.

Abstract

Starch was isolated from hulled (VJM 201) and hull-less (BL 134) barley with papain and aqueous sodium hydroxide treatments. For enzyme-assisted extraction, barley was steeped in water containing 0.2% SO2 + 0.55% lactic acid at 50° ± 2°C for 4-5h. The slurry was mixed with 0.4-2.0g papain/kg barley and incubated at 50° ± 2°C for 1-5h. Aqueous sodium hydroxide (0.01-0.05M) was added to the finely ground barley meal. The alkaline slurry was incubated at ambient temperature (25° ± 2°C) for 15-60min. The starch and grain fractions were isolated by screening and centrifugation. Increases in the time of treatment significantly affected the fiber, centrifugation and non-starch residue losses. Concentration of papain and sodium hydroxide had negligible effect on extraction losses. The enzyme-assisted extraction efficiency of starch was higher (80.7-84.6%) than the alkaline method (70.9-83.7%). The hulled barley showed higher extraction efficiency than the hull-less barley. The slurry treated with 0.4g papain/kg barley for 5h and 0.03M sodium hydroxide for 60min produced maximal yield of starch. Barley starch showed desirably high pasting temperature, water binding capacity and hold viscosity; and low final and setback viscosity compared with the commercial corn starch. The alkaline extracted hull-less barley starch showed exceptionally high peak and hold viscosities.