Preparation and Properties of Papain Precipitated from Fresh Latex of Papaya Fruits (Carica papaya)

Papain was precipitated from cysteine hydrochloride extract of fresh latex of papaya fruits planted in Alexandria Governorate, Egypt. Three precipitants; namely, ethyl alcohol, acetone and sodium chloride resulted in proteolytic activity recovery 84.8 (of three fractions), 85.2 and 76.7 %, respectively. Acetone was found to be the most promising rapid and simple conditions for preparing acetone dry powder of partially purified crude papain. Papain properties indicated that the maximum activity was attained at pH 7.5–8.0, and temperature of 75 -85°C. The activity was not affected by Na+ or Ca++ ions. Various degrees of inhibition were exerted by Ni+,+, Co++, Pb ++,and Hg++., while Cu++, caused complete inhibition .On the other hand, the proteolytic activity increased to various levels, in the presence of Sn++, cyanide, thioglycolic acid, and cysteine hydrochloride. The catalytic activation (49%) of Sn++ was found to depend to some extent on the concentration. A mixed stored papain-oryzae protease preparation ,was found to retain 71, 63, and 54 % of its proteolytic activity upon storage at 25°C for 1, 2 ,and 3 months ,respectively. The retained activity was more pronounced, being 92, 80,and 69 %, respectively upon storage at –5°C for the aformentioned durations, accordingly, storage at –5°C for up to 2 months, was recommended. The storage stability of papain powder and solutions were studied. A papain-oryzae protease preparation was formulated for further use in meat tenderization.