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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Starch Concentration and Mineral Oil on Crystallite Formation in Jet-Cooked Cornstarch Dispersions.

Authors
item Felker, Frederick
item Fanta, George
item Shogren, Randal
item Byars, Jeffrey
item Salch, John

Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: June 2, 2004
Publication Date: September 22, 2004
Citation: Felker, F.C., Fanta, G.F., Shogren, R.L., Byars, J.A., Salch, J. 2004. EFFECTS OF STARCH CONCENTRATION AND MINERAL OIL ON CRYSTALLITE FORMATION IN JET-COOKED CORNSTARCH DISPERSIONS.. American Association of Cereal Chemists Meetings. xx.

Technical Abstract: The development of a starch-oil composite technology based on excess steam jet cooking has led to further study of this processing method on starch itself. Previous work has shown that after jet cooking, starch dispersions which are allowed to slowly cool form toroidal, lobed, and spherical crystallites, depending on conditions. This study was made to examine effects of starch concentration on the types of crystallites formed, to determine the influence of mineral oil on their formation, and to partially characterize the crystallites by SEM, phase contrast microscopy, birefringence, and X-ray diffraction. In the absence of mineral oil, 4% starch yields a mixture of small toroidal crystallites and larger, symmetrical lobed crystallites. As starch concentration is increased to 10%, the size of the lobed crystallites increases, and they appear more spherical. Characteristic, banded birefringence patterns and X-ray diffraction patterns confirm the developmental relationship between the smaller, lobed form and the larger spherical form. When mineral oil is present, toroidal crystallites do not form. Instead, small (~1 micron), uniform aggregates of even smaller spherical particles appear, and these particles are associated with the lobed and spherical crystallites whose appearance and birefringence are altered by the attachment or inclusion of the small aggregates. Identification of the mechanisms for this crystallite polymorphism will allow the development of new applications for jet-cooked cornstarch.

Last Modified: 12/17/2014
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