Gelling properties of extruded yam (Dioscorea alata) starch

摘要

Yam (Dioscorea alata) starch was pregelatinized in a sing]e screw extruder. Response Surface Melhodo1ogy was used to study the effect of extrusion variables: feed moisture (l8, 2l. 24/100), extruder ten1perature (l20, l50. l80 deg C) and die diameter (3. 4. 5 mm) on cold viscosity. gel-forming capacity and retrogradation of extruded starches. Cold viscosity was higher from starch samples processed at higher moisture and die diameter, at lower temperatures. Slurries of the extruded starch (8/100, w/v, d .b. ) formed opaque and firm gels. Higher valles for gel strength were found in samples extruded at highest and lowest moistures at intermediate temperature and increasing die diameter. Gels of extruded starch had lower retrogradation values than non-extruded gelatinized starch after one and two weeks storage at refrigeration temperature. Prediction equations for the studied functional properties can be used in selecting processing conditions for specific food applications.