Storage and lyophilization effects of extracts of Cynara cardunculus on the degradation of ovine and caprine caseins

Clotting and proteolytic activities are important parameters when evaluating rennets for cheesemaking. Both these activities were determined for extracts of the plant Cynara cardunculus in fresh form and after lyophilization followed by reconstitution, either in water or in citrate buffer (pH 5.4) and stored for up to 4 weeks at 4°C. The patterns of degradation of ovine and caprine caseins were followed by urea polyacrylamide gel electrophoresis in attempts to qualitatively differentiate the activity of the enzyme extracts as storage time elapsed. Storage at 4°C significantly decreased the clotting power of the extracts but lyophilization retarded this decrease; β- and α(s)-casein breakdown generally increased with storage time, via patterns that depend on caseinate type and extract used, but lyophilized extracts reconstituted in citrate buffer were significantly less proteolytic than the other extracts. Therefore, it is suggested that lyophilized extracts (reconstituted with citrate buffer) of flowers of C. cardunculus be used rather than fresh extracts. Copyright (C) 2000 Elsevier Science Ltd.