Residual clotting activity and ripening properties of vegetable rennet from Cynara cardunculus in La Serena cheese

Vegetable rennet extracted from Cynara cardunculus flowers is traditionally used in the manufacture of La Serena cheese. High levels of proteolytic en zymes of the flowers are responsible for its clotting activity and strong p roteolytic action. The presence of residual coagulant in cheese and whey wa s measured by adding known amounts of vegetable rennet as internal standard . We found no differences between the residual coagulant activity of La Ser ena cheese compared with other types of cheese. The coagulant content detec ted at the end of four cheesemakings (vat of 830 l) in cheese and whey repr esented 27 and 78%, respectively, of the total amount added to milk. When m easurements were carried out in 16 different cheeses, vegetable rennet appe ared to be highly stable during cheese ripening. Cheese composition (moistu re, pH, NaCl, fat and protein) was kept relatively constant during ripening , which seems to contribute to stability of residual activity. Electrophore tic analyses of water insoluble fractions from cheeses manufactured with ve getable rennet showed that alpha(s)-casein was less susceptible to proteoly sis than beta-casein. The water soluble nitrogen/total nitrogen (WSN/TN) ex hibited higher levels only during the first 30 days of ripening although no n-protein nitrogen/total nitrogen (NPN/TN) ratio and amino acid nitrogen (N H2-N) increased with ripening time. (C) 1999 Canadian Institute of Food Sci ence and Technology. Published by Elsevier Science Ltd. All rights reserved .