Abstract:

This study was focused on reducing the soap content in corn oil by adsorption at freezing temperature. The effect
of the soap content and water content in degummed and deacidified corn oil, the addition of different amounts of diatomite
to the oil, stirring speed and crystal growing time on the soap residue after adsorption was examined. Using single factor
experiments and response surface methodology, the optimal process conditions for removing soap from corn oil were
determined as follows: addition of 0.4% diatomite to crude corn oil containing 321 mg/kg soap and 0.4% moisture, stirring
at 12 r/min, and 27 h crystal growth. Under these conditions, the residual soap in the oil was 23.1 mg/kg, and 92.8% of
the initial concentration was removed. The freeze-adsorption method was similarly effective as the conventional washing
process in reducing the soap content as indicated by the comparison of oil quality. On the other hand, the new method did
not need washing or drying. In addition, the method enabled pre-dewaxing and streamlined the processing steps. Without
producing sewage, it accomplished the purpose of energy conservation and environmental protection.

Key words: corn oil, freeze adsorption, percentage removal of soap, soap residue, without producing sewage