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Optimizing a Small-Scale Corn-Starch Extraction Method for Use in the Laboratory

¹Graduate student, postdoctoral research associate, and professor, respectively, 2312 Food Sciences Building, Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011. ²Currently, postdoctoral research associate, Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907-2009. ³Currently, assistant professor, Department of Food Science, The Pennsylvania State University, University Park, PA 16802. ⁴Corresponding author. Phone: 515-294-9688. Fax: 515-294-8181. E-mail: pjwhite@iastate.edu

The objectives of this experiment were to determine the effects of altering starch extraction procedures designed for use in the laboratory on starch yield, protein content, and thermal properties. Public Corn Belt inbred line Mo17 was used in this study. The altered procedures that were examined included steeping time (24, 48, or 72 hr), numbers of corn kernels extracted (2, 5, or 10 kernels), and isolation method (sedimentation or centrifugation). Starch thermal properties were obtained by using differential scanning calorimetry (DSC). Starch yield and protein content were significantly different among the experimental treatments. In general, more kernels, and sedimentation rather than centrifugation, resulted in greater yields. Also, treatments involving more kernels or sedimentation rather than centrifugation, yielded starch with the lowest protein content. Starch extracted after steeping for 24 hr and purified by the sedimentation method had the lowest gelatinization onset temperature (by DSC) and the widest gelatinization temperature range among the treatments. The energy required to gelatinize starch did not differ among the treatments. The differences among treatments in onset temperature and temperature range were probably caused by annealing of starch that occurs over time, during steeping. Therefore, to obtain the purest starch quality, this study suggests that sedimentation is preferred over centrifugation, and 10 kernels is preferred over 2 or 5. Furthermore, soaking the seeds for less than 24 hr is preferred if minimal annealing is desired.