The production of first-grade cottonseed oil primarily involves conventional refining. However, two parameters of cottonseed oil need additional processing steps:
1. Color: Conventional refining alone is not sufficient to achieve the desired color quality of cottonseed oil.
2. Low-Temperature Storage: Cottonseed oil may develop low-melting-point fats that cause poor transparency when stored at low temperatures. The deep color of cottonseed oil is mainly due to the presence of gossypol and its derivatives. Gossypol, found in the pigment glands of cottonseeds, is a significant pigment accounting for 20% to 40% of the total pigments. Gossypol can form very stable pigments when heated, increasing the difficulty of subsequent refining. Therefore, in the cottonseed extraction workshop, refining the mixed oil that has not been subjected to high-temperature treatment (as detailed below) is an effective method for reducing the color of cottonseed oil. Additionally, low-melting-point fats that precipitate during low-temperature storage require an extra fractionation step (as detailed below) to remove these substances from the cottonseed oil.