Variations of Polycyclic Aromatic Hydrocarbons in Vegetable Oils During Seed Roasting Pre-Treatment

Abstract

Seed roasting is a critical step for fragrant oil as it achieves the development of aroma and flavor, but also it is the way of polycyclic aromatic hydrocarbons and other harmful substances generated. In this study, for the purpose of mimic moderate roasting as well as powerful roasting condition, five oilseeds (peanut, sesame, sunflower, rapeseed and flaxseed) were submitted to roast at six selected temperatures (160 °C, 180 °C, 200 °C, 220 °C, 240 °C and 260 °C) for increasing time. The PAH levels in the five oils which obtained from corresponding roasted seed were quantified via GC-MS. The results showed that the concentrations and types of PAH substances in oils rapidly became more plentiful over seed roasting temperature and time, resulting an increase in total PAH concentrations, particular at temperature above 200 °C. The PAHs produced during the roasting of oilseeds may be mainly attributed to the lipid content and the degree of unsaturation (or P/S index) of the oilseeds. The higher lipid content in the oilseed, the easier it is to produce PAHs during seed roasting pretreatment. Oilseed with high polyunsaturated fatty acids tend to produce HPAH, on the contrary, low polyunsaturated fatty acids tend to produce LPAH.