Soy hull carbon as adsorbents of crude soy oil components: Effect of carbonization time

Studies were conducted to evaluate the performance of soy hull carbon adsorbents as affected by carbonization time. Carbonization was done by heating soy hulls to 400 degrees C for up to 30 min. Increased carbonization time resulted in elevated surface pH and titratable alkalinity. The effectiveness of adsorbents in binding minor soy oil components was studied. Free fatty acids content was decreased 70% with adsorbents carbonized for 30 min. Peroxides were adsorbed, but increasing carbonization time did not alter absorption by carbons. A similar trend was observed with the adsorption of total phospholipids. The residual lutein content of crude soy oil was not affected by the adsorbents. X-ray diffraction studies showed that carbonization at 400 degrees C converted the polysaccharide-based structure of soy hull to an amorphous, highly disorganized, random structure. Increase in carbonization time resulted in broadening of the diffraction pattern between 5 and 25 degrees 2 theta. Infrared spectra of soy carbon samples revealed presence of asymmetric C-H stretch, symmetric C-H bends, and C=O groups. The intensities of these spectra decreased with time of carbonization.