Food Chemistry 30 (1988) 19-27 Aqueous Protein and Gossypol Extraction from Glanded Cottonseed Flour: Factors Affecting Protein Coagulation and Gossypol Content A. H. E1 Tinay, A. M. Nour, S. H. Abdel-Karim & S. O. Mahgoub Department of Biochemistry,Faculty of Agriculture, Shambat, Sudan (Received 15 September 1987; revisedversion receivedand accepted 30 November 1987) ABSTRACT Protehl extracted from cold- and hot-de fatted cottonseedflour was recovered by isoelectric coagulation, dialysis, isoelectric coagulation after dialysis and isoelectric coagulation followed by dialysis of the whey. Isoelectric precipitation resulted in poor protein recovery, but dialysis caused considerable improvement in protein recovery. Isoelectric precipitation followed by coagulation of the remaining protein in the whey by dialysis resulted in the highest protein recovery. Isoelectric coagulation, after dialysis of the extract, gave a low protein recovery compared to that obtained by dialysis, but higher than that obtained by isoelectric coagulation alone. The protein and gossypol contents of protein isolates obtained from hot-defatted cottonseedflour were determined. The protein content of isolates obtained by dialysis was markedly high (above 90%) and their free gossypol content was low compared to isolates obtained by isoelectric coagulation. Increase of solvent to flour ratio decreased both total and free gossypol contents of protein isolates obtained by both methods. INTRODUCTION The biggest problem associated with cottonseed is the toxic pigment gossypol which must be removed before being eaten by monogastric animals (Noyes, 1969). Eckey (1954) reported that Gossypium hirsutum contains 19 Food Chemistry 0308-8146/88/$03-50 © 1988 Elsevier Applied Science Publishers Ltd, England. Printed in Great Britain