Oil recovery from condensed corn distillers solubles
Condensed corn distillers solubles (CCDS) contains more oil than dried distillers grains with solubles (DDGS), 20 vs. 12% (dry weight basis). Therefore, significant amount of oil is present in the liquid fraction after fermentation and ethanol distillation. The oil removed represents a significant alternative feedstock for biodiesel production. The objectives of the present research were to study the effect of enzyme hydrolysis on oil recovery from CCDS, to determine the effect of physical and chemical processes on oil recovery from CCDS, and to characterize quality of oil recovered from CCDS and the nature of deposits in CCDS oil. Employing enzyme processes with Protex TM 13FL (acid protease) increased oil recovery as enzyme concentration increased, with greatest oil recovery, 70% being achieved at 10% v/w (dry weight basis) enzyme concentration. Reducing the particle size of CCDS (by grinding) increased oil recovery, achieving 83% when Multifecty Pectinase and ProtexTM 13 FL were used. Zein-lipid interaction in a model system was strong such that only 10% of the oil could be freed by centrifugation alone. Following enzyme hydrolysis of the zein-oil complex with Alcalase 2.4L, oil recovery increased to 97%. For the physical and chemical processes, heating increased oil recoveries, 2.5-fold when temperature was increased from 25 to 59 yC. Oil recovery at acidic pH was significantly greater than at alkaline pHs. Oil extraction using isopropanol and butanol achieved > 80% total oil recovery. When oil was co-extracted with zein using hexane as a co-solvent, greatest total oil recovery achieved was 89%. Churning CCDS for 3 h at 50 yC and pH 3.5, up to 80% of the oil could be recovered. CCDS oil contains lipids (CCDS oil deposit) that solidify and settle to bottom of tank at ambient temperatures. This deposit had high free fatty acid (36%), high palmitic acid and wax contents causing a semi-solid appearance at ambient temperatures.