Impact of heat treatment on molecular composition of sunflower, cottonseed, and flaxseed oils
Abstract
This study presents a multiplatform analysis of sunflower, cottonseed, and flaxseed oils using FTIR, ¹H NMR, and GC-MS to evaluate compositional changes under heat treatment simulating deep frying. Prolonged heating at 180-250 °C increased trans-fatty acids (TFA) from <2% to ~4-6% in sunflower and cottonseed oils and up to ~20% in flaxseed oil. Saturated fatty acids (SFA) rose by ~10% across all oils. Sunflower and cottonseed showed notable reductions in polyunsaturated fatty acids, while flaxseed exhibited a sharp decline in monounsaturated fatty acids, from ~15% to <5% after extended heating. GC-MS revealed accumulation of free-/epoxy-fatty acids and aldehydes, alongside progressive tocopherol and phytosterol depletion. Results demonstrate that oil type is the dominant factor determining both baseline composition and thermal stability. Further research is needed to establish nutritionally safe and stable frying practices and elucidate compositional changes when oils interact with food ingredients during real-time cooking.