Several Studies Of High-Temperature Aging Vegetable Oil

In order to study the impacts of different heating condition (heating temperature and heating time) on molecular groups, molecular weight and molecular distribution, especially on rheological properties, The FTIR, GPC and advanced rheometer were applied to characterization. Meanwhile, Mixing different ratios of the fresh oil and aging oil to observe the influence of rheological properties of fresh oil while aging oil mixed in. Conclusion were shown as follows:1.The study Of vegetable oil in the mid-infrared region showed that the vegetable oil would darken in the heating process is not caused by the groups change;2. The vegetable oil groups will continue to react at room temperature after heating process indicated that new active substances produced in the heating process;3. The new substance gradually appeared in the heating process, which takes the molecular weights of oxidized triglycerides dimer, oxidized triglycerides trimer, etc. as the center. Extend the heating time or improve the heating temperature will promote the polymerization, express that the polymerization at 270℃get the highest degree,then 240℃,210℃,180℃ followed in turn. Oxidation kinetics show zero order kinetics is suitable for describing the polymerization under high temperature of soybean oil, but the oxidation reaction tends to first order kinetics when temperature goes higher;4. The viscosity of the vegetable oil will rise by the heating process. But the effect is not ideal while put it as a indicator to judge the degree of ageing or detect whether the aging oil had mixed into the fresh oil;5. Raising the heating temperature and extending the heating time, both will increase the loss modulus of the vegetable oil. So Loss modulus can be evaluated as an indicator of the degree of aging vegetable oil system, and the index can be a good guidance for the detection of cooking oil or adulterated oil.