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United States Department of Agriculture

Agricultural Research Service

Title: Thermal Properties of Starch in Corn Variants Isolated after Chemical Mutagenesis of Inbred Line B73

Authors
item Yamin, F - IOWA STATE UNIVERSITY
item Lee, M - IOWA STATE UNIVERSITY
item Pollak, Linda
item White, P - IOWA STATE UNIVERSITY

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1998
Publication Date: N/A

Interpretive Summary: Corn starch is widely used in food products. Because raw starch has physical and chemical limitations for use as food in these products, it is often modified with chemicals. Chemically modifying starch can be expensive and cause environmental problems, and the modified starch may not be as healthy for food uses as normal starch. Corn with natural modifications, however, can help prevent these problems. Corn seeds treated with a starch from the resulting ears analyzed to determine if the mutagen caused useful lines had different starch properties from the original corn line. The chemical mutagen likely changed the genes that affect starch structure. Further development of these lines could produce corn starch without the limitations of raw corn starch in food products. Results of our research could lead to "all-natural" processed food products which would be healthier and cheaper for the consumer.

Technical Abstract: The starch from eight ethyl methanesulfonate (EMS)-treated M4 families of the corn (Zea mays L.) inbred line B73 was analyzed by using differential scanning calorimetry (DSC), a rapid visco analyzer (RVA), and a texture analyzer (TA). The eight families were chosen from 144 families previously selected for having starch with unusual DSC parameters. Apparent amylose contents of the starch from the eight families generally were lower than that of the control. By DSC, starches from mutagenized families tended to have lower onset temperature (To) of gelatinization, enthalpy (delta-H of gelatinization, and peak height index (PIE), but broader gelatinization range (R) than the B73 control. Their values for delta-H and percentage of retrogradation (%R) were clustered around that of the control. Pasting properties from the RVA of the starches from the M4 families also were clustered around those of the control B73 starch, except for the setback values which were lower than B73 for M4 starches. Gel firmness values, as measured by the TA, of all the M4 starches were generally lower than that of the B73 starch at both storage treatments, 1 day at 25 deg. C and 7 days at 4 deg. C. The stickiness of the gels of the M4 starches tended to be greater than that of B73 after 7-day storage at 4 deg. C. The three observations were consistent with the lower apparent amylose values for the M4 starches. Possibly, EMS treatment altered the genes affecting internal structure of the starch granules. Starch from the mutagenized families likely had more than one population of starch granules, heterogeneous and regular granules, lower bonding forces among molecules, and fewer long chains in the amylopectin molecules than B73.

Last Modified: 4/20/2014
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