During use, oil composition changes as it interacts physically and chemically with food, oxygen and heat to create byproducts.  Some of these byproducts evaporate harmlessly while others stick around to change the nature of the oil.  Contaminants, including food particles, water and starches, migrate from food during and after normal cooking.  However, there are several ways operators can minimize potential oil contamination and slow changes in composition. For normal contaminants entering the oil during cooking, careful and frequent filtering, coupled with good fry station management, will remove solid contaminants including food particles and non-dissolved salts.

Frequent oil filtering removes sediment and contaminants from food, slows the creation of compounds that affect oil quality, and significantly extends oil life. Experts suggest that most operators filter oil at least once daily. In high volume operations and when frying heavily battered items, you should filter periodically throughout the day. With integrated or built-in filters, oil filtering can be conducted at start-up and at various times during the day when patron traffic in slower. Built-in filters make this process easier and more convenient for employees, increasing the likelihood that it actually happens.