Aroma modulation of vegetable oils—A review

Aroma is an important quality factor for unrefined vegetable oils especially the condiment oils, whose application and acceptability largely depend on their aroma attributes. The ever-advanced techniques including extraction, separation, detection and identification in flavor science allow hundreds of volatile compounds and aroma-active compounds with high complexity to be identified, which enables us a deep and comprehensive understanding of the aroma in various type of vegetable oils. Studies show that several avenues, mainly including enzymatic reaction, Maillard reaction, Strecker degradation, caramelization, lipid oxidation and thermal degradation of other compounds, account for the formation of these aroma compounds, though some may dominate over others depending on the processing methods/conditions. Based on these findings, novel approaches such as mild-heat treatment, roasting, microwave processing, infrared radiation, enzymatic treatment and fermentation, among others, have been applied to pretreat oil seeds or fruits with the aim to modulate the flavor generation and sensory quality in oils, whereby promising and insightful results are obtained. This review summarizes and discusses the volatile composition and key aroma compounds in common unrefined vegetable oils, their generation pathways as well as the approaches used to modulate their formations.