C. Chemical Composition

The chemical composition of corn consists primarily of protein, starch, and oil. While these attributes are not grade factors, they are of significant interest to end users. Chemical composition values 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 transit.

Summary: Chemical Composition

  • The U.S. Aggregate protein concentration in 2016 (8.6% dry basis) was higher than 2015, slightly higher than 2014, but lower than 5YA.

  • The Gulf ECA had lower protein concentrations than the other ECAs in 2016, 2015, 2014, and 5YA.

  • Average U.S. Aggregate starch concentration in 2016 (72.5% dry basis) was lower than 2015, 2014, and 5YA.

  • The Gulf ECA had higher starch concentrations than the Pacific Northwest and Southern Rail ECAs in 2016, 2015, 2014, and 5YA.

  • Average U.S. Aggregate oil concentration (4.0% dry basis) in 2016 was higher than 2015, 2014, and 5YA.

  • Chemical composition was less variable in 2016 than in the previous two years and 5YA (based on lower standard deviations for protein, starch, and oil).

Protein

Protein is very important for poultry and livestock feeding by supplying essential sulfur-containing amino acids and helping to improve feed conversion efficiency. Protein concentration tends to decrease with decreased available soil nitrogen and in years with high crop yields. Protein is usually inversely related to starch concentration. Results are reported on a dry basis.

Results

  • U.S. Aggregate protein concentration in 2016 averaged 8.6%, higher than 2015 (8.2%) and 2014 (8.5%), but lower than 5YA (8.7%).

  • U.S. Aggregate protein standard deviation in 2016 (0.50%) was slightly lower than 2015 (0.53%), 2014 (0.55%), and 5YA (0.60%).

  • Protein concentration range in 2016 (6.8 to 11.7%) was similar to the ranges in 2015 (5.6 to 11.3%) and 2014 (6.4 to 11.3%).

  • Protein concentrations in 2016 were distributed with 17% below 8.0%, 55.6% between 8.0 and 8.99%, and 27.4% at or above 9.0%. The protein distribution in 2016 shows fewer samples with low levels of protein than in 2015 or 2014.

  • Protein concentration averages for Gulf, Pacific Northwest, and Southern Rail ECAs were 8.5%, 8.8%, and 8.7%, respectively. The Gulf ECA had the lowest protein for 2016, 2015, 2014, and 5YA.

  • Based on U.S. Aggregate averages over the past six years, as protein concentration increases, true density increases (resulting in a correlation coefficient of 0.94), as shown in the figure to the right. Protein concentration appears to be lower in years with lower true density (2015) and higher in years with higher true density (2012).

Starch

Starch is an important factor for corn used by wet millers and dry-grind ethanol manufacturers. High starch concentration is often indicative of good kernel growing/filling conditions and reasonably moderate kernel densities. Starch is usually inversely related to protein concentration. Results are reported on a dry basis.

Results

  • Average U.S. Aggregate starch concentration (72.5%) in 2016 was lower than 2015 (73.6%), 2014 (73.5%), and 5YA (73.4%).

  • U.S. Aggregate starch standard deviation in 2016 (0.59%) was slightly lower than 2015 (0.61%), 2014 (0.63%), and 5YA (0.64%).

  • Starch concentration range in 2016 (69.2 to 74.3%) was similar to 2015 (70.5 to 76.3%) and 2014 (71.7 to 76.1%).

  • Starch concentrations in 2016 were distributed with 22.3% of the samples below 72.0%, 54.3% between 72.0 and 72.99%, and 23.4% at 73.0% and higher. The distribution shows more samples had lower levels of starch in 2016 than in 2015 and 2014. The lower concentrations of starch in 2016 were likely due in part to higher protein concentrations in 2016.

  • Starch concentration averages for the Gulf, Pacific Northwest, and Southern Rail ECAs were 72.6%, 72.2%, and 72.4%, respectively. Starch concentration averages were highest in the Gulf ECA in 2016, 2015, 2014, and 5YA. Thus, the Gulf ECA had the highest starch and lowest protein in 2016, 2015, 2014, and 5YA.

  • 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 negative correlation (-0.79) between starch and protein. 

Oil

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.

Results

  • Average U.S. Aggregate oil concentration (4.0%) in 2016 was higher than 2015 and 2014 (both 3.8%), and 5YA (3.7%).

  • U.S. Aggregate oil standard deviation in 2016 (0.23%) was lower than 2015 (0.30%), 2014 (0.31%), and 5YA (0.32%).

  • Oil concentration range in 2016 (3.2 to 4.9%) was narrower than 2015 (2.5 to 5.4%) and 2014 (2.8 to 5.0%).

  • Oil concentrations in 2016 were distributed with 13.1% of the samples at 3.74% or lower, 67.5% of samples at 3.75 to 4.24%, and 19.4% at 4.25% and higher.

  • Oil concentration averages for Gulf, Pacific Northwest, and Southern Rail ECAs were 4.0%, 4.1%, and 4.1%, respectively.