Abstract: Detoxified rapeseed meal solution was extracted by alkaline precipitation method to obtain phytic acid and the antioxidant activity of phytic acid obtained was evaluated through exploring its effect on acid value and peroxide value of lard using BHT as the positive control. Meanwhile, the antioxidant activity was also investigated through comparing its scavenging capacities against hydroxyl, superoxide anion and DPPH free radicals as well as hydrogen peroxide, determined by flow injection chemiluminescence and visible spectrophotometric methods, with those of VC. The results showed that the best condition for the extraction of phytic acid was pH 8. Under the optimal extraction condition, the yield of phytic acid was 92.83% and the purity was 45.96%. The extracted phytic acid could inhibit rancidity and peroxidation in lard with a better effect than that of BHT. The extract revealed the strongest scavenging effect against superoxide anion free radicals, followed by hydroxyl free radicals, hydrogen peroxide and DPPH free radicals. Moreover, it was superior to vitamin C in scavenging superoxide anion and hydroxyl free radicals. Therefore, the extract is a good natural antioxidant.

Key words: rapeseed meal, phytic acid, extractionl, free radical, antioxidant activity