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United States Department of Agriculture

Agricultural Research Service

Title: The Effect of Cooling Conditions on Jet-Cooked Normal Starch Dispersions

item Byars, Jeffrey
item Fanta, George
item Felker, Frederick

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 13, 2003
Publication Date: May 2, 2003
Citation: Byars, J.A., Fanta, G.F., Felker, F.C. 2003. THE EFFECT OF COOLING CONDITIONS ON JET-COOKED NORMAL STARCH DISPERSIONS. Meeting Abstract. xx.

Technical Abstract: When aqueous dispersions of normal corn starch are jet-cooked under excess steam conditions, the properties of the final product depend on the manner in which the cooked dispersion is 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 dispersion. A Rapid Visco Analyzer 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 hrs, 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 indicate that the cooling history of a cooked starch dispersion can significantly affect the properties of the final product.

Last Modified: 4/18/2015