Location: Plant Introduction ResearchTitle: Effect of Planting Date on Cornstarch Stuctures and Properties) Author
Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 6/14/2010
Publication Date: 10/24/2010
Citation: Medic, J., Abendroth, L., Elmore, R., Blanco, M.H., Jane, J. 2010. Effect of Planting Date on Cornstarch Stuctures and Properties [abstract]. In: Cereal Foods World. American Association of Cereal Chemists Meetings. 55:A59. Interpretive Summary:
Technical Abstract: Because of unexpected weather conditions during planting season, many growers have to plant corn before or after the optimal planting date. A significant delay in planting corn reduces grain yields, but the effect on starch structures and properties is not well understood. We obtained grains of B73 and a commercial corn hybrid planted at Ames and Nashua, IA at three to five planting dates from April 16 to June 11 of 2008. Structural and functional characteristics of isolated starches were studied. Starch from corn planted early (April 16 and April 30) contained a significant number of very large granules with diameter >20 µm, whereas corn planted on June 11 had homogeneous granule size distribution with fewer large granules. These results suggest that with early planting dates, some starch granules had more time to develop into a larger size. The apparent amylose content of cornstarch decreased with the delay in planting time from 25.38% (db) to 24.56%, and 24.28% to 23.35% for the commercial hybrid and B73, respectively. For the commercial hybrid, there was a decreasing trend in the average chain length of amylopectin from 21.1 to 20.0 glucose units with delayed planting dates, with the exception of the corn planted April 16 (19.8). The molecular weight of amylopectin was not significantly affected by the planting dates. The onset, peak, and final gelatinization temperatures of the commercial hybrid starch decreased with the delay in planting dates from 62.74°C to 60.65°C, 68.12°C to 65.53°C, and 72.34°C to 71.09°C, respectively. The pasting temperature and setback viscosity of the commercial hybrid starch decreased from 70.15°C to 69.5°C, and 96.05 RVU to 91.33 RVU, respectively, but the peak viscosity increased from 161.96 RVU to 177.25 RVU with the delay in planting dates. The enzyme hydrolysis of starch in ground corn showed that corn samples planted earlier were less digestible than those planted later. The exception was the sample planted April 16, which showed slow hydrolysis rate in the beginning, but a very fast rate in the later stage of hydrolysis. In conclusion, planting time significantly affected structural characteristics of the cornstarch and consequently, altered its functional properties.