Deep frying is one of the most used worldwide methods in food preparation, but controlling the oil quality
(temperature and formation of polar compounds) is crucial. The main objective of this work was to assess the
practices of food handlers with regard to the frying processes in social food services located in Navarra (a region
of northern Spain). The study was performed in two phases: in the first one, a self-administrable questionnaire
regarding the usual practices on food deep-frying processes was sent to the food services through the main social
catering companies of Navarra participating in the study. In the second one, in situ monitoring of the frying
practices was performed as verification tools of frying practices reported by food services and to check the oil
quality. Almost half of the fryers exceeded the maximum recommended temperature to avoid the formation of
toxic compounds (175 ◦C). Despite only one the fryers exceeded the maximum limit of polar compounds
established by current Spanish regulation, the obtained values indicated that the oil had begun to degrade in 20%
of the fryers. Oil temperature is an important factor that affects the quality of the oil. In addition, significant
differences were found between the different frequencies of change or types of oils. We have noticed a lack of
knowledge in relation to the risks associated to the bad management of frying oil. Therefore, it would be
desirable to improve food handlers training in relation to this matter. Defining a periodic frequency of oil change
according to its use and periodic controls of temperature and polar compounds (as part of the Hazard Analysis
and Critical Control Point system), could be adequate tools to improve management of frying oil in food services