Microwave pretreatment effects on the changes in seeds microstructure, chemical composition and oxidative stability of rapeseed oil

• Tocopherol contents depending on both the MV time and rapeseed moisture content.
• MV pretreatment of rapeseed did not alter the fatty acid composition of oils.
• MV irradiation significantly increased concentration of canolol in rapeseed.
• An increase of canolol content resulted in markedly improved oxidative stability.

The purpose of the present study was to investigate the effect of microwave (MV) irradiation on the microstructure of rape seeds, recovery of oil, and to examine changes in oxidative stability, composition of FA, and contents of tocochromanols and canolol of rapeseed oil. Rapeseeds (Brassica napus) of two varieties, Kana and Bakara, adjusted to moisture contents of 7 and 9%, undergone MV pretreatment under 800 W for 0, 3, and 7 min, prior to oil extraction by cold-press. Tocochromanol contents were differently affected by the MV pretreatment of rapeseed prior to pressing. Depending on the adjusted seed moisture content both individual and total tocopherol contents increased to the maximum at different microwave times. The amount of canolol detected in cold-pressed oil samples ranged from 16.34 to 16.97 μg/g of oil; this was increased to 926.42 and 821.86 μg/g by MV pretreatment for 7 min (at 7% moisture level). The oxidative stability prolongation from 3.64 to 4.09 h up to 11.52–12.75 h was observed. Regarding the FA composition of the oils, no significant changes (P > 0.05) in the fatty acid composition occurred during seeds MV pretreatment.