Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2009
Publication Date: August 18, 2009
Citation: Liu, K.S. 2009. Fractionation of Distillers Dried Grains with Solubles (DDGS) by Sieving and Winnowing. BioResource Technology. 100:6559-6569. Interpretive Summary: Distillers dried grains with solubles (DDGS) is a major co-product of bio-ethanol production from corn and other grains. It is a mixture of particulate material, containing roughly 10% moisture, 25% protein, 10% oil, 4% ash and 50% carbohydrate. Currently, it is used mainly as feed of ruminant animals. With increasing production of bio-ethanol in recent years, there is a great need to study DDGS and find new ways to enhance its quality and end use values. Accordingly, this applied study was conducted. It focused on dry fractionation of DDGS by sieving, winnowing and their combinations. Results show that the selected processing methods, particularly the combination of the two, were effective in dry fractionating DDGS samples, and resulted in production of at least two major types of fractions, a protein and oil enriched fraction and a fiber enriched fraction. The protein and oil enriched DDGS could be better used as feed for non-ruminant animals (including fishes) and as food ingredients. Fiber enriched fractions could be better used for production of corn fiber oil, corn fiber gum, or cellulose-based ethanol. Thus, dry fractionation of DDGS not only enhances nutritional values of certain fractions but also would expand market shares. Furthermore, enhanced DDGS could potentially sell at a higher price.
Technical Abstract: Four commercial samples of distillers dried grains with solubles (DDGS), were subjected to sieving and then winnowing. All sieved fractions except for the pan fraction, constituting about 90% of original mass, were subjected to winnowing with an air blast seed cleaner. Sieving was effective in producing fractions with varying composition. As the particle size decreased, protein and ash contents increased, and total carbohydrate (CHO) decreased. Winnowing sieved fractions was also effective in shifting composition, particularly for these of larger particle classes. Heavy sub-fractions were enriched in protein and oil while light sub-fractions were enriched for CHO. As the velocity of air flow increased, light sub-fraction mass increased, while the compositional difference between the heavy and light sub-fractions decreased. Winnowing three times at a lower velocity was as effective as winnowing one time at a medium velocity. For protein, there was a balanced effect between sieving and winnowing, while combination of the two resulted in a maximum 56.4% reduction in a fraction and maximum 60.2% increase in another fraction. Winnowing was more effective than sieving in changing oil and CHO contents. Winnowing the whole sample of DDGS 4 was not as effective as sieving winnowed fractions in changing composition, but their combined effect appeared comparable to that of sieving followed by winnowing.