Submitted to: Carbohydrate Polymers
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2005
Publication Date: 8/1/2005
Citation: Peterson, S.C., Fanta, G.F., Adlof, R.O., Felker, F.C. 2005. Identification of complexed native lipids in crystalline aggregates formed from jet cooked cornstarch. Carbohydrate Polymers. 61(2):162-167. Interpretive Summary: When cornstarch is jet cooked and cooled slowly, two different types of crystalline particles (larger spherical and smaller torus-shaped) have been found in the resulting solutions. It is not clear what controls the formation of one type of particle over the other. Past literature has shown that both of these particles are made up of molecular complexes of starch and the native lipids that are in cornstarch. The goal of this study was to determine what types of lipids were in each type of crystalline particle and see if they were a determining factor in the type of particle formed. It was discovered that the percent composition of the lipids in the spherical-shaped particle matched that of the starting cornstarch very closely, while the torus-shaped particles did not. A separate experiment also showed that when the jet cooked cornstarch is slowly cooling, the spherical particles form first, at higher temperatures, followed by the smaller torus-shaped particles. Understanding how and why these two shapes of crystallites form may allow us to control future jet cooking reactions with more precision and control, which could potentially be used to create specific encapsulation products and applications.
Technical Abstract: Crystalline aggregates, resulting from crystallization of helical inclusion complexes of amylose with the native lipids in jet cooked cornstarch, exhibit two distinct morphologies: smaller, torus-shaped and larger, spherical/lobed particles. Gas chromatographic analyses of extracted lipids showed that these two species contained mixtures of the same native lipids found in granular cornstarch, although in different relative amounts; especially the 16:0 (palmitic) and 18:2 (linoleic) components. The torus-shaped particles contained about twice as much palmitic as linoleic acid; whereas these ratios were reversed in the lipids extracted from the spherical/lobed particles. These findings are consistent with X-ray diffraction data. Microscopic examination of crystalline aggregates formed at different temperatures showed that the spherical/lobed particles are the first to form, and that the torus-shaped particles form at a lower temperature. The fact that the composition of the lipid mixture extracted from the spherical/lobed particles closely resembles that of the lipid mixture extracted from cornstarch itself is consistent with the fact that these particles are the first to form.