Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2002
Publication Date: 12/30/2002
Citation: Byars, J.A., Fanta, G.F., Felker, F.C. 2002. THE EFFECT OF COOLING CONDITIONS ON JET-COOKED CORN STARCH DISPERSIONS. American Association of Cereal Chemists Meetings. xx.
Technical Abstract: When aqueous dispersions of normal corn starch are jet-cooked under excess steam conditions, their properties depend on the manner in which they are cooled. Phase separation of amylose and amylopectin dramatically alters the final properties, and the extent of phase separation depends on the processing history of the sample. The aim of this study was to determine the effects of cooling rate, stirring rate and starch concentration on the rheology and microstructure of the cooled dispersions. A Rapid Visco Analyser was used to obtain a range of cooling profiles and stirring rates. Rheological measurements showed that samples that were stirred during cooling had higher viscosities and were more elastic than unstirred samples. Light microscopy revealed incipient phase separation of amylose and amylopectin in samples cooled immediately after jet cooking. After gradual cooling for 4 hours, both irregular, amorphous particles, and spherical or toroidal crystalline particles were observed in various proportions depending on starch concentration, cooling rate, and stirring during cooling. These results correlate with the extent of phase separation, and they indicate that the cooling history of a jet-cooked starch dispersion can significantly affect the properties of the final product. Specifically, controlling these factors will enhance development of applications for jet-cooked corn starch.