Formation of trans fats during food preparation

Can J Diet Pract Res. 2012 Summer;73(2):98-101. doi: 10.3148/73.2.2012.98.


Purpose: An investigation was completed to determine how typical cooking procedures used in food preparation, such as baking and stir-frying, affect trans fats formation.

Methods: Canola oil was used as the main fat ingredient. Zucchini cake and gingersnap cookies were baked at 180o C and 200o C, while stir-fried chicken was prepared at 200o C and 275o C. The lipids from the food were extracted following the Folch procedure, and analyzed for trans fatty acids according to ISO official method 15304.

Results: Minimal changes were observed in the amount of trans fats during baking. Application of extreme temperatures during baking, which caused carbonization of the outer layer of products, yielded an insignificant increase in the amount of trans isomers. As with baking, stir-frying did not result in significant isomerization of the fatty acids, even when the oil was heated to 275o C and smoking heavily before the food was placed in it. Irrespective of the cooking procedure, linolenic acid was the most prone to isomerization with the highest amount of trans isomers formation.

Conclusions: Baking and stir-frying at normal and/or extreme temperatures do not significantly affect the amounts of trans fats. Likewise, heating oil to the smoking point during stir-frying may decrease the amount of polyunsaturated fatty acids because of oxidative degradation.

MeSH terms

  • Cooking / methods*
  • Fatty Acids, Monounsaturated / metabolism*
  • Fatty Acids, Unsaturated / analysis
  • Fatty Acids, Unsaturated / metabolism
  • Hot Temperature*
  • Oxidation-Reduction
  • Plant Oils / metabolism*
  • Rapeseed Oil
  • Trans Fatty Acids / analysis*
  • Trans Fatty Acids / metabolism*


  • Fatty Acids, Monounsaturated
  • Fatty Acids, Unsaturated
  • Plant Oils
  • Rapeseed Oil
  • Trans Fatty Acids