| The extraction of free gossypol from cottonseed kernel by methanol was studied so as to reduce the toxicity of cottonseed meal and extract gossypol efficiently. On the basis of single factor experiment, the extraction conditions were optimized by response surface methodology. The results showed that extraction time had the most significant effect on the extraction rate of free gossypol, followed by ratio of solid to liquid, extraction temperature and stirring rate; the optimal extraction conditions were obtained as follows: ratio of solid to liquid 1∶24, extraction temperature 35℃, extraction time 42 min, stirring rate 2 600 r/min and extraction times twice(first extracting for 21 min with ratio of solid to liquid 1∶12, then also extracting for 21 min with ratio of solid to liquid 1∶12). Under the optimal conditions, the extraction rate and the purity of free gossypol reached 68.9%±0.81% and 81.9%±0.85% respectively, and the residue of free gossypol in cottonseed meal was 839.7 mg/kg, which was lower than the allowed maximum residue of free gossypol 1 200 mg/kg in cottonseed cake and cottonseed meal in hygienical standard for feeds (GB 13078—2001). |
