1, primary oil and secondary oil are highly refined. After degumming, deacidification, decoloration and deodorization, it has the characteristics of tasteless, light color, high smoke point, less cooking fume and difficult solidification at low temperature. After refining, the content of harmful components in primary oil and secondary oil is low, and many nutrients are lost;
2. The refining degree of the tertiary oil and the tertiary oil is low, and only through simple degumming, deacidification and other processes. Its color is dark, the smoke point is low, and the oil smoke is large during cooking. Due to the low degree of refining, the impurities in the third and fourth grade edible oils are high, and some carotene, chlorophyll and vitamin E are also retained.
3. The primary and secondary oils have high purity and low impurity content, and can be used for cooking at higher temperature, such as stir-frying. Third-and fourth-grade oils are not suitable for high-temperature heating and can be used to make soups and stews.