Crude extract of sunflower seeds was prepared using different extractants (distilled
water, 5% NaCl in distilled water, 5% NaCl in acetate buffer pH 5.0) and certain mixing ratios (1:2,
1:5 and 1:10 seeds powder : extractant, respectively). Using of 5% NaCl in acetate buffer pH 5.0 at
mixing ratio of 1:5 gave an extract with reasonable efficient clotting properties. Ammonium sulphate
at 40-60% concentration was used in one single step for the partial purification of the extract.
Ammonium sulphate, (40-60%) fraction showed milk clotting and specific activities of 440 sec and
2.30 U/mg protein, respectively. Meanwhile a yield percentage and a fold of purification of 28.58 and
2.02 were achieved. Clotting/proteolytic activity, water holding capacity and curd synersis of the
partially purified extract approved those of commercial calf rennet indicating the suitability of the
extract as a rennet substitute. The optimum temperature, pH, Cacl2 and GDL concentration of the
resultant extracts were found to be 65°C, 5.0, 0.04 % and 0.4%, respectively.