STUDIES ON KARKADE (HIBISCUS-SABDARIFFA) - PROTEASE INHIBITORS, PHYTATE, IN-VITRO PROTEIN DIGESTIBILITY AND GOSSYPOL CONTENT

Karkade defatted flour extract had chymotrypsin inhibitor activity alm ost half that of trypsin (21.8 and 40.5 enzyme inhibitor activity unit s/mg protein, respectively). The protein isolate had a weak chymotryps in inhibitor activity compared to that of tryprin (4.9-28.3 enzyme inh ibitor activity units/mg protein, respectively). The trypsin inhibitor activity of the protein isolate was 70% of that of the defatted flour extracts. Extraction of trypsin inhibitor by citrate buffer (pH 4.6) gave a higher specific activity of trypsin than by phosphate buffer (p H 7.6), Tris buffer (pH 9.0) or distilled water. Heating the extract i n boiling water for 10 min destroyed 66.1% of the trypsin inhibitor ac tivity. Karkade protein isolate had lower free and total gossypol than did the whole seed and defatted flour. The in vitro protein digestibi lity of karkade defatted flour and protein isolate was lower than that of casein. Phytic acid was higher in karkade defatted flour than in s oybean defatted flour. (C) 1996 Elsevier Science Ltd.