Caseinolytic and milk-clotting activities from Moringa olezfera flowers

This work reports the detection and characterization of caseinolytic and milk-clotting activities from Moringa oleifera flowers. Proteins extracted from flowers were precipitated with 60% ammonium sulphate. Caseinolytic activity of the precipitated protein fraction (PP) was assessed using azocasein, as well as alpha(s)-, beta- and kappa-caseins as substrates. Milk-clotting activity was analysed using skim milk. The effects of heating (30-100 degrees C) and pH (3.0-11.0) on enzyme activities were determined. Highest caseinolytic activity on azocasein was detected after previous incubation of PP at pH 4.0 and after heating at 50 degrees C. Milk-clotting activity, detected only in the presence of CaCl2, was highest at incubation of PP at pH 3.0 and remained stable up to 50 degrees C. The pre-treatment of milk at 70 degrees C resulted in highest clotting activity. Enzyme assays in presence of protease inhibitors indicated the presence of aspartic, cysteine, serine and metallo proteases. Aspartic proteases appear to be the main enzymes involved in milk-clotting activity. PP promoted extensive cleavage of kappa-casein and low level of alpha(s)- and beta-caseins hydrolysis. The milk-clotting activity indicates the application of M. oleifera flowers in dairy industry. (C) 2012 Elsevier Ltd. All rights reserved.