Cashew nut oil: effect of kernel grade and a microwave preheating extraction step on chemical composition, oxidative stability and bioactivity

The cashew nut kernels can be broadly classified by colour, size, quality and integrity, into whole (W), butts (B), splits (S) and P (pieces). This work evaluated seven sizes and qualities of cashew kernel (B1, S1, W4, SP1, SP2, P2 and W240), for oil extraction. Then, two oil extraction methods, using cold pressing (CP) and microwave preheating (MP), respectively, were investigated. In evaluation of cashew kernel grades, the fat content varied between 51.6 and 57.6g100g(-1), and the acidity and peroxide were low, indicating good chemical quality for all grades. The oil extracted by MP showed a higher induction time in the Rancimat test (46.25h). The cashew nut oil showed bioactivity, mainly associated with the level of total phenolic compounds (CP: 202.17mg100g(-1); MP: 371.95mg100g(-1)), and showed antiproliferative activity against cancer cells (lung, breast and liver) but only at high concentrations. The MP extraction preserved many components and increased the phenolic compounds in the cashew kernel oil, without promoting negative changes in its physicochemical and oxidative qualities.