Proteolytic and clotting activity in Cynara scolymus leaves: new horizons for the cheese manufacture

Increasing cost and shortage of animal rennet have encouraged new researches for different rennet sources. New aspartic proteinases of vegetable origin are nowadays of growing interest for dairy technology (Durante et al., 2009). Among plant species, extract from flowers of Cynara genus is the most used for cheesemaking. In particular, several studies have been performed on the activity and specificity of proteinases from Cynara cardunculus, whereas, the knowledge on the properties of globe artichoke (Cynara scolymus) proteinases is limited because its flower is usually consumed as a vegetable. In this study we have investigated the presence of proteinases in different parts of Cynara scolymus such as leaves, pappus and roots that represent by-products always disposed off by farmers. By measuring the proteolytic activity on k-casein and milk clotting activity with a sensitive method called caseogram (Foltman et al., 1985) we proved that only leaves possess the proteolytic enzymes showing the optimum activity at pH 5. Hence, the proteinases were partially purified through ammonium sulfate precipitation (from 20% to 80% (w/v)) and ion-exchange chromatography. Interestingly, our results demonstrated the presence of two species with a different electrophoretic mobility. Therefore, based on these findings, the present study could suggest the possibility of use such new proteases having proteolytic and clotting activity in cheesemaking.