| To improve the utilization ratio of protein resources from cottonseed meal, the preparation process of polypeptides from the hydrolysis of gossypol removed cottonseed meal by composite protease was investigated. Taking the yield of polypeptides and degree of hydrolysis as the evaluation indexes, the different types of proteases on hydrolysis capability of protein from cottonseed meal were compared, and a composite protease composed with trypsin and Aspergillus oryzae protease in a enzyme activity ratio of 3∶?1 was determined as the optimal protease for the hydrolysis process. Then, the hydrolysis process conditions, including protein mass concentration of cottonseed meal, enzyme dosage, pH, hydrolysis temperature and hydrolysis time were analyzed and optimized by single factor experiment and response surface methodology. And the optimal process conditions were determined as follows: protein mass concentration of cottonseed meal 25 g/L, enzyme dosage 5 000 U/g, pH 8.91, hydrolysis temperature 50-55?℃ and hydrolysis time 5.92 h. Under the optimal conditions, the yield of polypeptides was 71.85%. The results of amino acid composition showed that polypeptides could effectively maintain the amino acid composition of cottonseed meal protein, the variety of amino acids was complete, contents of eight kinds of essential amino acids were abundant and the nutritive value was high. |
