Title: Nutrient concentrations and proportions in particle size fractions of corn steam flaked to different bulk densities Authors
Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2010
Publication Date: September 15, 2010
Citation: Hales, K.E., Cole, N.A., Galyean, M.L., Leytem, A.B. 2010. Nutrient concentrations and proportions in particle size fractions of corn steam flaked to different bulk densities. Professional Animal Scientist. 26(5):511-519. Interpretive Summary: Corn grain is commonly processed before feeding to finishing beef cattle in the Southern Great Plains. Steam flaking is the most widely used processing method. It involves the application of heat, moisture, and mechanical action to disrupt the starch structure and increase digestibility of corn grain. When the bulk density of steam-flaked corn is decreased, starch availability is increased, therefore increasing the feeding value. Little research is currently available to characterize the particle size distribution and corresponding nutrient profiles of steam-flaked corn processed to varying bulk densities. Therefore, we conducted a grain processing experiment to describe the distribution of nutrients in particles of varying sizes in steam-flaked corn processed to three bulk densities. Steam-flaked corn processed to bulk densities of 22, 26, and 30 (pounds/bushel) was sieved to determine the proportions in particle size fractions ranging from greater than 8,000 um to less than 600 um, and total starch, crude protein, neutral detergent fiber, phosphorus, ether extract, and ash concentrations were determined in the resulting fractions. The greatest proportion of particles was in the greater than 8,000-um fraction, whereas the smallest proportion was associated with the 600-um sieve fraction. The proportion of total starch, crude protein, neutral detergent fiber, and ash present in particles greater than 8,000 um decreased as flake bulk density decreased. In addition, the proportion of total starch within particle sizes of 4,760 to 8,000, 1,180 to 2,360, and 600 to 1,180 um was greater for 22 than for 26 and 30 pounds/bushel flakes. Within the range of bulk density of steam-flaked corn evaluated, some nutrients accumulated in finer particles created during the steam flaking process. In conclusion, if smaller particles are disproportionately sampled, flaked corn would seem to differ in composition from the intact grain.
Technical Abstract: The particle size distribution that results from steam flaking corn could be responsible for the difference in the chemical composition noted between steam-flaked corn and unprocessed grain. Steam-flaked corn (SFC) processed to bulk densities of 283, 335, and 386 g/L was dry sieved to determine the proportions in particle size fractions ranging from > 8,000 µm to < 600 µm, and total starch, crude protein (CP), neutral detergent fiber (NDF), phosphorus (P), ether extract (EE), and ash concentrations were determined in the individual fractions. Data were analyzed as a completely randomized design using the four to six batches of corn that were flaked as experimental units. Concentrations of CP, NDF, P, EE, and ash of the intact flakes were not affected (P >/= 0.09) by flake bulk density. The greatest dry weight proportion of particles in grab samples was in the > 8,000-um fraction with the smallest proportion was associated with the 600-um sieve fraction. The proportion of NDF, P, EE, and ash present in particles >8,000 um decreased (P < 0.05) as flake bulk density decreased. In addition, the proportion of total starch within particle sizes of 4,760 to 8,000 and 1,180 to 2,360 um was greater (P </= 0.02) for 283 than for 335 and 386 g/L flakes. Within the range of bulk density of SFC evaluated, certain nutrients were more concentrated in the finer particles created during the steam flaking process. If smaller particles are disproportionately under-sampled, flaked corn would appear to differ chemically from the grain being flaked.