Promotive Effect of Shearing-Force on Cold Water Solubility and Gelatinization of Low Moisturized Starch Melt at an Elevated Temperature

Abstract

Kyushu Uniuersity, 6-1O-1, Hakozaki, Higashi-ku, Fuleuoka 812 Heated and heated-sheared starches (corn, wheat, potato and sweet-potato starches containing 20 and 25% moisture(dry basis)) at l50°C were prepared with a flow tester and then cold water solubility and the degree of gelatinization were compared. For heated samples, cold water solubilities of corn, wheat, potato and sweet-potato starches containing 20% moisture were only 3.5, 3.7, 1.8 and 5.6%, respectively while for heated-sheared samples, they were 48.3, 28.5, 33.2, and 51.0% (as the average value of 30-500kg/cmcm² samples), respectively. For heated samples, the degrees of gelatinization of corn, wheat, potato and sweet-potato starches were 38.4, 40.6, 24.7 and 28.8%, respectively although for heated-sheared samples of starches, they increased up to 85.6, 90.3, 89.8 and 84.0 (ast, eaverage value of samples treated at 30-500kg/cmcm²), respectively. The trends were same for starch samples containing 25% moisture. The results of the present experiments conducted that the shearing-force on starch melt may strongly influence the increase of cold water solubility and the degree of gelatinization of low moisturized starch under heating.