Flavor enhancement of strong fragrant rapeseed oils by enzymatic treatment

Fragrant rapeseed oils with the sensory characteristics attract increasing market in China. The unique flavor of strong fragrant rapeseed oil (SFRO) is the first choice to attract the consumers' preference. Thus, enzymatic treatments of rapeseeds were used to enhance the flavor properties of SFROs in the present study. Results showed that SFRO produced from neutral protease and α-amylase-treated rapeseeds (NRO+ARO) had the highest percentages of unsaturated fatty acid (USFA), monounsaturated fatty acid (MUSFA) and oleic acid (C18:1) of 93.30%, 65.90% and 65.22%, respectively, with the highest tocopherol content of 577.35 mg/kg and total sterol content of 4523.46 mg/kg. The NRO+ARO showed a strong nutty and rich roasted fragrance and distinguishing sweet flavor with the highest overall sensory evaluation score. Majority of volatile compounds in NRO+ARO belonged to pyrazines and furans originated from Maillard reactions with the highest contents. The highest decrease trends of monosaccharide and amino acid contents from 8.42 g/kg to 2.04 g/kg and from 128.91 mg/kg to 47.39 mg/kg, respectively, were observed in the neutral protease and α-amylase-treated rapeseeds after roasting. Glucose/xylose-lysine reaction products contained the high contents of pyrazines, suggesting enhancement of supply of glucose/xylose and lysine in rapeseeds would significantly improve the fragrance of SFROs. The outputs of present study would provide a clue to understand the formation of unique flavor of SFROs and a reference to develop series of SFRO products.