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 evaluatin g rennets for cheesemaking. Both these activities were determined for extra cts of the plant Cynara cardunculus in fresh form and after lyophilization followed by reconstitution, either in water or in citrate buffer (pH 5.4) a nd stored for up to 4 weeks at 4 degreesC. The patterns of degradation of o vine and caprine caseins were followed by urea polyacrylamide gel electroph oresis in attempts to qualitatively differentiate the activity of the enzym e extracts as storage time elapsed. Storage at 4 degreesC significantly dec reased the clotting power of the extracts but lyophilization retarded this decrease; beta- and alpha (s)-casein breakdown generally increased with sto rage time, via patterns that depend on caseinate type and extract used, but lyophilized extracts reconstituted in citrate buffer were significantly le ss proteolytic than the other extracts. Therefore, it is suggested that lyo philized extracts (reconstituted with citrate buffer) of flowers of C. card unculus be used rather than fresh extracts. (C) 2000 Elsevier Science Ltd. All rights reserved.