Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 3, 1998
Publication Date: N/A
Technical Abstract: Corn products--starch (CS), fiber (CF), ground corn cobs (GCC), corn gluten meal (CGM), and distillers' dried grains (DDG) were each thermochemically reacted with citric acid (CA) to generate citrate derivatives. Citrate derivatives of the first three were each generated by oven heating 1:1 w/w material/CA for 24 hrs. Whereas CGM and DDG derivatives were generated by two passages of 1:1 w/w mixtures through a Brabender-PlastiCorder PL 2000 (3/4" laboratory extruder), single screw, 30:1 L/D, fitted with 1/1 screw and no die; zone temperatures were 140, 200, 196 deg C; speed was 20 rpm. The resulting citrate derivatives from either process were finely ground and water washed at pH 2 to remove unreacted CA to yield acid-insoluble derivatives. Each derivative was oven dried at 75 deg C for 24 hrs and reground. These derivatives (ie 1.000 g) were each dispersed in 100 mL of metal ion solution where metal ion concentration was calculated to be approx. 200mg/L; pH was adjusted to 4.5 with 1N NaOH to give a charged ligand. Metal chelates were formed with Pb(NO3)2, CdCl2, AgNO3, ZnSO4, CuSO4, CoCl2, NiSO4, FeSO4, and MnSO4. The ability of citrate derivative to chelate metals varied. In general, CS/CA derivatives gave highest degree of binding with metal ions, whereas both DDG/CA and CGM/CA bound Pb2 better than all others. Comparison of metal binding ability of CS/CA with a sulfonic acid, styrene type analytical grade cation exchange resin (AG50W-X8 from Bio-Rad Laboraties, Richmond, CA) showed the CS/CA derivative to have 37-81% of the capacity to bind metals than the petroleum based product where ability to bind metals varied with metal ion bound. The biobased metal chelators produced in our study can be generated at a considerable cost savings when compared with petroleum based products.