Submitted to: Proceeding of Plains Nutrition Council Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2002
Publication Date: 4/25/2002
Citation: Drager, C.D., Dew, P.F., Brown, M.S., Cole, N.A. 2002. The effect of degree of corn processing on the chemical composition of corn [abstract]. In: Proceeding of Plains Nutrition Council Symposium, April 25, 2002, Amarillo, Texas. Publication No. AREC 02-20, Texas A&M Research and Extension Center, Amarillo, Texas. p. 126.
Technical Abstract: An experiment was conducted to determine the effect of degree of processing on the chemical composition of corn. Corn was processed by dry rolling to a bulk density of 0.59 kg/L (46 pounds/bushel, DR46) or steam flaking to a bulk density of 0.36 or 0.28 kg/L (28 [SF28] and 22 [SF22] pounds/bushel, respectively). Each treatment was prepared on a given day, and treatments were replicated on ten days. On each day, unprocessed corn was cleaned and bagged (34 kg each), and bags were randomized to treatment. Dry rolled grain was prepared initially, and SF22 and SF28 were prepared in random sequences; samples of processed and unprocessed corn were collected. The coefficients of variation for nutrient concentrations (% of DM) in unprocessed corn (includes assay variation, pooled across days) were: ash (14.5%); ADF (17.1%); NDF (8.5%); CP, automated N combustion procedure (2.7%); CP, Kjeldahl N procedure (3.3%); P (6.1%); Mg (7.5%); K (7.0%); Na (27.1%); total starch (8.8%); available starch (8.8%); available starch, % of total starch (9.5%). For each variable, the unprocessed nutrient concentration was included in the statistical model as a covariate for analyzing the corresponding processed corn nutrient, and covariates remained in the model when significant (P < 0.10). Increasing the degree of processing decreased ash content (linear, P < 0.001; 2.12, 1.76, and 1.59 ± 0.09 % of DM for DR46, SF28, and SF22, respectively). A quadratic response (P = 0.03) was observed for ADF content (2.8, 2.8, and 2.4 + 0.1%), whereas NDF decreased linearly (10.9, 9.6, and 8.4 + 0.3%). Total starch (67.6, 69.8, and 74.4 + 1.3%), Kjeldahl assay CP (9.2, 8.6, and 8.2 + 0.07%), and combustion assay CP (8.9, 8.3, and 7.9 + 0.07%) decreased linearly (P < 0.002) as degree of processing increased. Potassium (0.42, 0.32, and 0.26 + 0.01%), P (0.34, 0.24, and 0.18 + 0.01), and Mg (0.12, 0.08, and 0.06 + 0.004%) concentration decreased linearly (P < 0.0001), whereas Na responded quadratically (P = 0.03; 0.07, 0.09, and 0.07 + 0.005%) as degree of processing increased. The sum of assayed minerals of DR46, SF28, and SF22 accounted for 45, 41, and 36% of ash content, respectively. These data suggest that processing corn decreases the concentration of phosphorus (29 to 47%), potassium (24 to 38%), magnesium (33 to 50%), crude protein (8 to 11%), and neutral detergent fiber (11 to 23%). Further research is needed to determine potential avenues of nutrient disappearance and(or) limitations in analytical determination.