Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract only
Publication Acceptance Date: 5/10/2008
Publication Date: 9/21/2008
Citation: Liu, K. 2008. Relationships of Particle Size Distribution, Compositional and Color Properties between Ground Corn and Distillers Dried Grains with Solubles (DDGS). American Association of Cereal Chemists Meetings. Spet. 21-24 Honolulu, Hawaii. Interpretive Summary:
Technical Abstract: A major process for making ethanol from corn is dry-grind method, by which, the first step is to grind corn into powder whereas the last step is to recover a co-product, distillers dried grains with solubles (DDGS). Oftentimes, corn processors believe that ground corn and DDGS are interrelated in certain quality parameters. Yet, previous research, although rather limited, has shown no scientific basis for it. In this study, six ground corn and resulting distillers dried grains with solubles (DDGS) samples were collected from different ethanol processing plants in the U.S. Midwest area. Particle size distribution (PSD) by mass was determined using a series of six selected U.S. standard sieves: No. 8, 12, 18, 35, 60, and 100, and a pan. The original sample and sieve sized fractions were measured for contents of moisture, protein, oil, ash and starch, and surface color. Total carbohydrate (CHO) and total non-starch CHO were also calculated. Results show that the geometric mean diameter (dgw) of particles was different among corn and DDGS samples, and that dgw of DDGS was larger than that of corn (0.696 vs. 0.479 mm, average values), indicating that during conversion of corn to DDGS, certain particles became enlarged. For dgw and mass frequency of individual particle size classes, the relationship between ground corn and DDGS varied, but particle size distribution was well correlated between corn and DDGS (r = 0.807). Upon conversion from corn to DDGS, on an average, protein was concentrated 3.59 times; oil, 3.40 times; ash, 3.32 times; and total non-starch CHO, 2.89 times. There were some positive correlations in contents of protein and non-starch CHO and in L value between corn and DDGS. However, actual variations in nutrients and color attributes were larger in DDGS than in corn, and for the same sample, variation was larger in sieved fractions than in whole fraction. Raw material, processing method and addition of yeasts are among major factors considered for causing large variations in these attributes of DDGS, whereas raw corn exerted its effect through concentration resulting from starch depletion. The study partially supports the common belief by processors that quality attributes of corn affect those of DDGS.