Abstract:

Although detection methods for waste edible oil are currently available, these methods have defects. According
to our theoretical analysis, those materials which are hard to remove during refining of waste edible oil contain carbonyl or
hydroxyl groups. In this study, two methods were presented to identify waste edible oil by measuring carbonyl and hydroxyl
values, respectively. Used cooking oils had an obviously higher hydroxyl value than fresh ones. There was an over three-fold
increase in the hydroxyl value as compared with the fresh cooking oils, even though the used cooking oils were refined. Thus
hydroxyl value is a specific indicator to identify waste edible oil.

Key words: waste edible oil, hydroxyl value, diglyceride, comprehensive detection index system