Cottonseed Protein Isolated Extraction Technology

As an important protein source, the cottonseed protein has rich supply. However, its application range and content in animal feed has been limited because of containing the free gossypol and some anti-nutritional factors. In order to use the protein resources effectively, this study discussed the extraction process so as to obtain a higher extraction rate, at the same time reduce the content of free gossypol.This text studied the extracting temperature, extracting time, pH value, solid-liquid ratio and extracting times which are the factors affecting the extraction of cottonseed protein by using lower concentration of NaOH solution. The result showed that the gossypol content was reduced significantly and got a higher purity of the protein using this method. The experiment determined the optimum conditions by orthogonal test: pH 7-8, temperature 50℃, time 3h, solid-liquid ratio 1:10, the extracting rate was up to 63.77% and the purity of protein was 90% which reached the standerd of separated protein, gossypol content decreased to 0.043%.Using NaCl for the solution of cottonseed protein extraction, the effecting factors NaCl concentration, time and temperature were studied. The results indicated that it could get higher purity of protein except that the removal of gossypol had no significant effect. The optimum extraction condition were NaCl concentration 2.6%, temperature 40.5℃and extracting time 1.96h which were determined through RSM. The extracting rate was up to 54.5% and the purity of protein was 92% which reached the standerd of separated protein, gossypol content decreased to 0.051%.The free gossypol content was reduced significantly using NaOH extraction of cottonseed protein combined the treatment by methanol. After that the cottonseed protein accorded fully with the food safety standard. The experiment could reduce gossypol content to 0.02% using methanol: extracting solution =0.8:1.Amino acid analysis result showed that the essential amino acids in the extracted cottonseed protein accounted for 29.6% of the effective amino acids. Besides the ratio of lysine and methionine was hige, so the cottonseed protein had a higher nutritional value.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) was used to analyze the separated cottonseed protein, the result showed that the cottonseed protein content was about 60% and the main components was low molecular spherical protein. The cottonseed protein contained six subunits, the molecular weight were respectively 49kd, 43kd, 33kd, 26kd, 18kd, 14d.The functional properties of the separated cottonseed protein were studied, including water absorption, oil absorption, emulsifying and emulsion stability, foaming capacity and foam stability. The comparison between cottonseed protein and soy protein was also studied. The results showed that the cottonseed protein has higher water absorption, emulsification, emulsion stability and oil absorption, the applicability is also relatively good, the foaming is relatively poor.