Abstract: The effects of microwave or roasting preptreatment on the acid value, peroxide value, fatty acid composition, antioxidant activity and volatile flavor components of cold pressed double low rapeseed oils were studied. The results showed that the acid value of cold pressed rapeseed oil in the two pretreatment groups ranged from 0.64 to 0.88 mg/g and the peroxide value ranged from 1.65 to 1.95 mmol/kg. The acid value and peroxide value of cold pressed rapeseed oil were affected by either pretreatment, but both of them remained within the range of the quality standard for cold pressed rapeseed oil. Microwaving and roasting had no significant effects on the fatty acid composition of cold pressed rapeseed oil. The antioxidant activity of rapeseed oils with different pretreatments, as evaluated by 1,1-dipheny1-2-picryl-hydrazyl (DPPH) radical scavenging capacity, could be ranked as follows: roasting at 180 ℃ for 15 min > roasting at 180 ℃ for 10 min > microwaving for 2 min > roasting at 180 ℃ for 5 min > microwaving for 90 s > microwaving for 1 min > control without any pretreatment. A total of 42 volatile flavor components were detected in the seven rapeseed oils, mainly including sulfide, glucosinolate degradation products and heterocyclic compounds. Microwaving and roasting had significant effects on volatile flavor components of rapeseed oils. With the extension of microwaving and roasting time, the characteristic volatile flavor compounds of rapeseed oils changed from glucosinolate degradation products to pyrazines, and the overall flavor changed from sulfureous and green aroma to baked and nutty aroma.

Key words: pre-processing techniques; cold pressed double low rapeseed oil; quality; volatile flavor components