Comparison of protein concentrate, protein isolate and wet sieving processes for enriching DDGS protein

Distillers dried grains with solubles (DDGS) is a coproduct of the dry grind ethanol process. Due to its high fiber content, use of DDGS is limited as an ingredient in ruminant animal diets. Reducing fiber and increasing protein content will increase the value of DDGS. Further increase in protein content and decrease in fiber content can be achieved by removing oligosaccharides and other soluble carbohydrates from DDGS. Two DDGS samples were produced: one using the conventional dry grind process (conventional DDGS) and another using a modified dry grind process (E-Mill DDGS). Three protein enrichment processes were used on E-Mill and conventional DDGS. These enrichment processes were protein concentrate and isolate processes, adapted from soybean industry, and a wet sieving process. For E-Mill DDGS, protein contents of protein concentrate, protein isolate and sieved coproducts were 48, 52 and 51 % (db), respectively, compared to 42 % (db) for E-Mill DDGS. For conventional DDGS, protein contents of protein concentrate, protein isolate and sieved coproducts were 33, 37 and 40 % (db), respectively compared to 34 % (db) for conventional DDGS. Among the three processes, the wet-sieving process resulted in the highest protein content for conventional and E-Mill DDGS samples.