AbstractBACKGROUNDCanola oil processing generates as by‐products cakes rich in proteins, which have high nutritional value. These cakes contain an expressive amount of phenolic compounds which are important as antioxidants, but can interfere in proteins nutritional value. The aim of this work was to identify the phenolic compounds present in canola seed cake and to maximize their extraction by investigating the factors: temperature (20–70 °C), ethanol concentration in water (0–85%) and sample/solvent ratio (1:5–1:20).RESULTSThe maximum phenolic compounds amount was obtained at 65 °C, ethanol concentration of 35% and sample/solvent ratio of 1:20. At this condition, more than 95% of these compounds were extracted from the canola seed cake. It was observed that the solvent could be re‐used for additional extractions, reducing the solvent consumption. A large number of phenolic compounds were identified (24 compounds) and quantified, including sinapic acid derivatives, flavonoid glycosides derivatives and major and minor sinapoyl choline derivatives.CONCLUSIONThe phenolic compounds can be easily extracted from the canola seed cake, resulting in a cake with low antinutrients content and, in contrast, an extract rich in antioxidant compounds with possible use as a natural source of antioxidants. © 2019 Society of Chemical Industry