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Predicting Extractable Starch In Corn Varieties With NIT

Marvin R. Paulsen Marvin R. Paulsen
Dept.of Agricultural Engineering
(217) 333-7926; mpaulsen@illinois.edu
Mukti Singh

Mukti Singh
Research Assistant
Dept.of Agricultural Engineering
(217) 265-5020; mbajaj@illinois.edu


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).

Foss Infratec 1229 NIT grain analyzer

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 2,073
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.

Histogram of laboratory 100-g extractable starch values

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.

Calibration equation predicting the validation set of 389 samples

Figure 3. Calibration equation predicting the validation set of 389 samples.


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