Refrying foods repeatedly in a thin layer of oil can lead to significant accumulation of oxidized products within 20-30 minutes.

“In restaurants, however, when you are frying something, especially if you are frying in a thin layer of oil, the research shows like going from like a I want to say it's like a 1 cm to like 5 cm of oil, huge difference in how quickly oxidized and u negative products will start to form. And if you are having oil that you are frying, reffrying in over and over and over, yes, they're within certainly with a thin layer, within 20 30 minutes, you can start to have significant amounts of these negative products accumulating.”