| Marvin R. Paulsen
Dept.of Agricultural Engineering
(217) 333-7926; email@example.com
In 2001, the U.S. produced about 9.51 billion bushels of corn. Of these, 2.03 billion bushels were used for food and industrial uses (Corn Annual, 2002). Of these 2.03 billion bushels, wet milling, fuel, and beverage alcohol utilized 1.84 billion bushels. Thus, about 19 percent of the corn produced in the U.S. involves starch extraction. Extractable starch refers to the amount of starch that can be recovered from a maize kernel by the wet milling process. Extractable starch percentages are lower than starch content and often are reduced due to severe drying, genotype, and year-to-year growing conditions. A combination of wet harvest moistures and kernel-drying temperatures over 140°F are very detrimental to extractable starch and can cause a five to six percentage point reduction in extractable starch (Paulsen et al., 1999). Each improvement of one percentage point in extractable starch has a value of about 4 to 6 cents per bushel (Paulsen et al., 1999).
Figure 1. Foss Infratec 1229 NIT grain analyzer.
A calibration for the Foss Infratec 1229 NIT instrument was developed
for extractable starch in corn (Figure 1). Since 1997,
over 2,200 samples have been scanned and have had laboratory reference values
performed based on the 100-g wet milling test of Eckhoff et al. (1996).
Extractable starch can range from 51 to 71 percent dry basis, as shown in
(Figure 2). A calibration developed in spring 2002 had
samples with extractable starch greater than 50 percent dry basis and moistures greater than 9 percent wet basis (Paulsen and Singh, 2002). Mean extractable starch was 65 percent. Approximately one-fifth or 389 samples were randomly selected and removed from this data set to use as a validation set. Using Infra Soft International (WinISI Version 1.5) software, a calibration was developed. When predicting the validation data set, the standard error of prediction (SEP) was 1.34 with an R2 of 0.80 and an RPD (ratio of standard deviation to SEP) of 2.2, as shown in (Figure 3). The NIT calibration provides a potential tool for screening varieties high in extractable starch.
Figure 2. Histogram of laboratory
100-g extractable starch values for 2,073 samples
of maize between 7 and 25 percent moisture and more than 50 percent extractable
starch for 1997 through 2001 crop years.
Figure 3. Calibration equation predicting the validation set of 389 samples.
Corn Annual. 2002. U.S. Corn Refiners Association, Inc. Washington, D.C. 20006.
Eckhoff, S.R., K. Singh, B.E. Zehr, K.D. Rausch, E.J. Fox, A.K. Mistry, A.E. Haken, Y.X. Niu, S.H. Zou, P. Buriak, M.E. Tumbleson, and P.L. Keeling. 1996. A 100-g laboratory corn wet milling procedure. Cereal Chemistry. 73(1):54–57.
Paulsen, M.R., S.W. Mbuvi, A.E. Haken, B. Ye, and R.K. Stewart. 1999. Extractable starch as a quality measurement of dried corn. ASAE Paper No. 99-6023. ASAE. St. Joseph, MI.
College of Agriculture, Consumer and Environmental Sciences
University of Illinois Extension
© 2002 University of Illinois
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