Quality and safety of frying oils used in restaurants.

Fresh, in-use and discarded frying oils were collected from randomly selected restaurants in downtown Toronto, Canada, in order to assess the oxidative and hydrolytic state of oil used in commercial practice and consumed regularly by the local population. All in-use and discarded samples showed extremely high levels of oxidation products based on the p-anisidine value (p-AV) (7.6<p-AV<56.5), bringing into question the toxicological safety of foods prepared with such oils. High peroxide values (PVs) (PV>10meq/kg) and free fatty acid (FFA) levels (FFA>1%) suggested that 30-35% of in-use frying oils and 45-55% of discarded oils were not acceptable. However, total polar compounds (TPCs), the most widely used measure of frying oil quality in Europe, suggested that the oils were of acceptable quality (15.5>TPC). The TPC test was found to greatly underestimate oil degradation. We recommend that National Public Health authorities include frying oil inspections in their monitoring programs.