Soy hull as an adsorbent source in processing soy oil

Abstract

Soy hull, a co-product of the soybean industry, was evaluated as an adsorbent source for processing soy oil. Ground soy hull (<100 mesh), boiled soy hull, and soy hull carbon were each added to crude soy oil at various levels in the laboratory under commercial bleaching conditions. The free fatty acid (FFA), peroxide value (PV), pigments, and total phospholipid contents (PL) of treated samples were measured. The microstructure (scanning electron microscopy, SEM), X-ray diffraction patterns (XRD), and Fourier transform infrared (FTIR) spectra of the soy hull adsorbents were also examined. The soy hull carbon was more efficient as an adsorbent relative to the ground or boiled soy hulls. The differences between ground and boiled soy hulls in the reduction of FFA were not significant. The effectiveness of adsorbents to reduce PV was: soy hull carbon > boiled soy hull = untreated soy hull; and for PL adsorption: soy hull carbon = ground soy hull > boiled soy hull. Boiling resulted in an open, porous structure, as evident from the SEM data, but carbonization did not affect the particle size. The XRD patterns of ground and boiled soy hulls were similar to those of powdered amorphous cellulose, but the carbon was more amorphous and had a random structure, as well as a more polar surface, as revealed by the FTIR spectra.