Compositional profile and variation of Distillers Dried Grains with Solubles from various origins with focus on non-starch polysaccharides

Corn-, wheat- and mixed cereal Distillers' Dried Grains with Solubles (DDGS) were investigated for compositional variability among DDGS origins, ethanol plants, and the relationship between corn and corresponding DDGS. A total of 138 DDGS samples were analyzed by use of Near Infrared Reflectance Spectroscopy for common constituents, while 63 DDGS samples along with 11 corn samples were characterized for their non-starch polysaccharide (NSP) content. The results indicated that the compositional profile of DDGS reflected the nutrient content of the parent grain but with a greater content of remaining nutrients (e.g. protein, fat, fibre and minerals) after fermentation of starch to ethanol. Corn DDGS differentiated from wheat DDGS by a greater content of fat (P≤0.006), insoluble-NSP (P<0.001), uronic acids (P<0.001), cellulose (P=0.032), and arabinose/xylose (P<0.001) - and uronic acid/xylose-ratio (P<0.001). Wheat DDGS differentiated from corn DDGS by a greater content of ash (P=0.001), soluble-NSP (P<0.001), and Klason lignin (P<0.001). Among the three sources of DDGS, the greatest variation was observed for the content of soluble-NSPs, especially soluble arabinoxylan. Based on the compositional profiles of the DDGS, principal component analysis allowed for a visual differentiation of corn DDGS from five different ethanol plants, indicating the potential of each ethanol plant to produce DDGS with consistent compositional characteristics. Furthermore, investigation of corn and corresponding DDGS indicated that the NSP fraction is modified during the fermentation process, especially arabinoxylan, by an increase in soluble arabinoxylan proportion in DDGS. In addition, the arabinose/xylose (P<0.001) and uronic acid/xylose-ratio (P<0.001) were greater for corn, compared with corresponding DDGS, indicating modifications of the endosperm arabinoxylan during the fermentation and drying process.