Heat induced changes in hydroxy-, epoxy- and dihydroxy-PUFA in Edible Oils

Abstract

Vegetable oils are a main ingredient in our daily food. Most vegetable oils contain high levels of polyunsaturated fatty acids (PUFAs). For example sunflower and rapeseed oil are rich in linoleic acid (C18:2n6, LA) while the later also contains relevant amounts of a-linolenic acid (C18:3n3, ALA). These PUFAs are prone to oxidation, leading to the formation of a large variety of oxidized fatty acids. These oxylipins include hydro(pero)xy-, epoxy-, and dihydroxy-PUFA.

We investigated the formation and degradation of these oxylipins in vegetable oils during food processing. In particular, we evaluated the differences between cold-pressed and refined oils. This includes the changes occurring at every stage of the refining process: Degumming, in case of chemical refinement neutralization, bleaching and deodorization. During refining, changes were observed only in the bleaching and deodorization step, including a reduction of E,Z-hydroxy(peroxy)-PUFA during bleaching an deodorization.

In the talk, we will present how levels of specific oxylipins are changed during the process of industrial refining in the main vegetable oils, such as sunflower and rapeseed oil. Additionally, we will present how the reactions occurring during thermal treatment of oils might allow to discriminate between virgin and refined oils. The heat induced changes are compared to our previous studies (J Agric Food Chem, 2023, 71(19) 7508) on the effect of frying on the formation and degradation of oxylipins.