FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Rheological properties of condensed corn distillers solubles


In the paper, the rheological properties were presented of condensed fraction of corn distillers solubles (CCDS) originating from the production of ethanol. In the samples analyzed, the content of dry matter ranged from 10 to 40 % of CCDS. The measurements were performed using a rotational and oscillatory shear flow. It was proved that the CCDS suspensions were fluids showing complex rheological properties. Their characteristics were that of thixotropic fluids, and, within the concentration range from 25 to 40 %, the yield stress was present. To describe the flow curves at an increasing and decreasing shear rate, a Herschel-Bulkley model was applied. The yield stress values of fresh suspensions varied in the range from 3.2 Pa for CCDS of a 25% concentration rate to 46.7 Pa for CCDS of a 40 % concentration rate. The destruction of CCDS microstructure in the shear flow caused the yield stress values to decrease fourfold. Based on the oscillation tests, it was confirmed that a gel microstructure was formed in the fluid at rest. That microstructure was destroyed in a rotational shear flow, which, at the same time, prevented its complete reconstruction. On the other hand, the reconstruction of that microstructure was observed in the oscillatory flow. The microstructure reconstruction time was strongly dependent on the CCDS concentration rate. For the concentrations rates of 25 % and 30 %, the complete reconstruction of the microstructure occurred after 8060 and 10350 s. In the case of the CCDS concentration rates of 35 and 40 %, 54 and 45 % of the fluid microstructure was reconstructed during the ongoing experiment (10 800 s).


distillery grains, rheology, thixotropy, yield stress, corn, gel