Functional properties of pregelatinized and cross-linked cassava starch obtained by extrusion with sodium trimetaphosphate

Cassava starch was cross-linked with sodium trimetaphosphate (STMP) on a Cerealtec single-screw extruder at different extrusion temperatures and concentrations of STMP and NaOH. The effect of variables on functional properties of the products was analysed by the response¯surface methodology. The degree of substitution (DS) was influenced by NaOH and phosphorus level, and increased when their concentration increased. Extrusion temperature affected water absorption, cold viscosity and gel characteristics. The introduction of phosphate groups by cross-linking, with maximum DS of 1.5×10-4, increased the gel strength, water absorption index, resistance to high temperature and shear, and decreased gel cohesiveness, starch clarity and water solubility index. The products had different DS and degree of gelatinization and thus can be applied in several kinds of foods.