C. Chemical Composition
Chemical composition of corn is important because the components of protein, starch and oil are of significant interest to end users. The chemical composition attributes are not grade factors. However, they provide additional information related to nutritional value for livestock and poultry feeding, for wet milling uses, and other processing uses of corn. Unlike many physical attributes, chemical composition values are not expected to change significantly during storage or transport.
Protein is very important for poultry and livestock feeding. It supplies essential sulfur-containing amino acids and helps to improve feed conversion efficiency. Protein is usually inversely related to starch content. Results are reported on a dry basis.
- In 2013, the U.S. Aggregate protein averaged 8.7%, which was significantly lower than the 9.4% found in 2012, but the same as the 8.7% found in 2011.
- Protein ranged from 6.5 to 13.3% with a standard deviation of 0.66% for the U.S. Aggregate corn.
- Protein standard deviation in 2013 was similar to 0.66% and 0.60% found in 2012 and 2011, respectively.
- Protein was distributed with 48.9% between 8.0% and 8.99%, 26.2% between 9.0% and 9.99%, and 7.4% at 10.0% or higher.
- Protein averages for Gulf, Pacific Northwest, and Southern Rail ECAs were 8.5%, 9.1%, and 9.1%, respectively.
Starch is an important factor for corn used by wet millers and dry-grind ethanol manufacturers. High starch content is often indicative of good kernel maturation/filling conditions and reasonably high kernel densities. Starch is usually inversely related to protein content. Results are reported on a dry basis.
- The U.S. Aggregate starch averaged 73.5% in 2013, significantly above the 73.0% found in 2012, and higher than 73.4% found in 2011.
- Starch ranged from 71.1% to 75.9% with a standard deviation of 0.65% for the U.S. Aggregate.
- Starch was distributed with 21.8% between 72.0% and 72.99%, 49.7% between 73.0% and 73.99%, and 24.9% equal to or greater than 74.0%, and was similar to the distribution in 2011.
- Starch averages for the Gulf, Pacific Northwest, and Southern Rail ECAs were 73.5%, 73.4% and 73.2%, respectively.
Oil is an essential component of poultry and livestock rations. It serves as an energy source, enables fat-soluble vitamins to be utilized, and provides certain essential fatty acids. Oil is also an important co-product of corn wet and dry milling. Results are reported on a dry basis.
- U.S. Aggregate oil averaged 3.7% in 2013. Average oil has been fairly constant over the three years.
- Oil ranged from 2.0 to 5.0% with a standard deviation of 0.34% for the U.S. Aggregate.
- Oil standard deviation in 2013 was similar to 0.34% and 0.31% found in 2012 and 2011, respectively.
- Oil was distributed with 39.2% of the samples at 3.25 to 3.74%, and 35.6% of samples at 3.75 to 4.24% and 8.5% at 4.25% and higher.
- Oil averages for Gulf, Pacific Northwest, and Southern Rail ECAs were 3.7%, 3.5% and 3.7%, respectively.
SUMMARY: CHEMICAL COMPOSITION
- The lower protein in 2013 compared to 2012 is likely attributable to the 2012 crop experiencing the drought. During the 2012 growing season, available nitrogen was distributed over fewer corn metric tons per hectare (or fewer bushels per acre), causing protein percentages to be higher in 2012 than in 2013 or 2011. The U.S. Aggregate average protein in 2013 is most likely closer to the long run average protein level.
- Starch content (73.5%) was significantly higher in 2013 compared to 73.0% in 2012, but nearly the same as that found in 2011. Since starch and protein are the two largest components in corn, when the percentage of one goes up the other usually goes down. This relationship is illustrated in the adjacent figure showing a weak but negative correlation between starch and protein. The correlation coefficient is -0.57. The higher starch may indicate good kernel filling that should be desirable for corn wet milling.
- Since the phase-out of high-oil corn from past years, oil content has been fairly constant averaging about 3.7%, (standard deviation 0.34%) during the past three years.