A study of vegetable (thistle) rennet in the production of Flor de Guía cheese

The Protected Designation of Origin for Flor de Guía Cheese includes two fundamental requirements: the exclusive use of vegetable (thistle) rennet from Cynara cardunculus var. ferocisisima or Cynara escolymus, as a milk coagulant, and to use certain percentages of milk with respect to the species of origin. These two variables, depending on the random criterion of the cheese-maker, give us the interest of knowing the possible influence they may have on the production process and therefore also on the variability of the final characteristics of the cheese. Thus, the proposed objectives were to study the influence of the use, on the one hand, of different concentrations of thistle (C. cardunculus) on the coagulation of different milk types and, on the other, of different mixtures of milk types (of different species) on the coagulation time. The tests for the coagulant activity were carried out following the Berridge technique modified by the NOVO method, obtaining the enzymatic solution from dried thistle flowers in maceration provided by a cheesemaker. The assays showed increased coagulant activity as the concentration of thistle extract increased (especially at low concentrations and on sheep and cow milk) as well as the percentage of sheep milk in the mixtures used as substrate. Further investigations about the use of these two variables, combining high percentages of sheep's milk and thistle extracts of moderate strength, will need for improving the sensory characteristics of Flor de Guía cheese