Publication no. C-2000-0412-03R |  VIEW ARTICLE

Extrusion of Cross-Linked Hydroxypropylated Corn Starches I. Pasting Properties (1).

A. E. McPherson (2), T. B. Bailey (3), and J. Jane (2,4). (1) Journal paper no. J-18471 of the Iowa Agriculture and Home Economics, Experiment Station, Ames, IA, Project No. 3258. (2) Graduate student and professor, respectively, Center for Crops Utilization, Research and Department of Food Science and Human Nutrition, Iowa State University. (3) Professor, Department of Statistics, Iowa State University. (4) Corresponding author. E-mail: <jjane@iastate.edu> Cereal Chem. 77(3):320-325. Accepted January 5, 2000. Copyright 2000 American Association of Cereal Chemists, Inc.

A series of cross-linked (0, 0.014, 0.018, 0.024, and 0.028% POCl(3), dry starch basis) hydroxypropylated (8%) corn starches were extruded using a Leistritz micro-18 co-rotating extruder. Process variables included moisture, barrel temperature, and screw design. Differential scanning calorimetry and X-ray diffraction studies showed the level of starch crystallinity decreased with increasing severity of extrusion conditions. Pasting properties of the extruded starches were examined using a Rapid Visco Analyser. Pasting profiles of starches extruded at different conditions displayed different hot paste viscosity and final viscosity. Increasing starch moisture content during extrusion and level of cross-linking increased starch viscosity (P < 0.0001), whereas increasing extrusion temperature and shear decreased starch viscosity (P < 0.0001). Interactions were found between level of cross-linking and screw design and between extrusion temperature and starch moisture content (P < 0.0001).