Abstract: In an attempt to investigate the effect of different preparation methods on the quality and shelf life of Qinghai flaxseed oil, Qinghai flaxseed was pretreated by baking in an electric oven or far infrared oven, high-pressure high-temperature wet heating, degumming or vacuum freeze drying before being used for oil preparation by screw pressing or hydraulic pressing. The oil yield, peroxide value, acid value, moisture content and volatile component contents, fatty acid composition, volatile components and total phenol content of flaxseed oil were determined. A kinetic model for the oxidation of flaxseed oil was established by using the Schaal oven method to predict the shelf life. The results showed that the oil yield and total phenol content of flaxseed oil prepared by electric oven baking combined with screw pressing was significantly higher than those of the samples prepared by the other methods. Meanwhile, the peroxide value, acid value, moisture content and volatile component contents were lower than those of the other samples, and the shelf life was the longest, 353 days. The sample prepared by electric oven baking combined with screw pressing had the largest number of volatile components (72), compared to 40–60 for the other samples. Different preparation methods had significant effects on the volatile components of flaxseed oil. In addition, the content of linolenic acid was the highest among the five major fatty acids of flaxseed oil, ranging from 54.71 to 61.03 g/100 g. However, different preparation methods had no significant effect on the fatty acid content of flaxseed oil. Compared with those prepared by the other methods, the quality of flaxseed oil obtained by electric oven baking combined with screw pressing was better.

Key words: flaxseed oil; pretreatment; preparation method; quality analysis; shelf life