The effect of different thermal histories (different heating time and heating temperatures) on the changes of relative molecular weight and its distribution of soybean oil was measured by gel permeation chromatography(GPC)with the oil injection mode,and the analysis results were fitted. The results indicated that the novel substances gradually appeared in the heating process, which took the center relative molecular weights of triglycerides dimer, triglycerides trimer, etc. Extending the heating time or improving the heating temperature could promote the polymerization of oil, showing that the degree of polymerization at 270℃ got the highest, followed by 240, 210, 180℃. The study result of oxidation kinetics of soybean oil indicated that zero order reaction was suitable for describing the polymerization at high temperature, while the oxidation reaction tended to first order reaction when temperature went higher. |