Optimization of Milk-Clotting Conditions and Rheological Properties Characterization of a Plant-Based Coagulant from Onopordum platylepis Murb. in Ewe’s Milk

Plant-derived coagulants are increasingly explored as alternatives to animal rennet. This study provides the first evaluation of the coagulation kinetics and technological properties of Onopordum platylepis Murb. in ewe’s milk. Response surface methodology was applied to optimize temperature (30, 33, and 36 °C), pH (5.5, 6.0, and 6.5), and calcium chloride concentration (2, 4, and 6 mM). The optimal conditions for minimizing milk-clotting time were 36 °C, pH 5.5, and 6 mM CaCl2. Under standardized activity (50 IMCU/L), the Rheological properties of gels produced by Onopordum platylepis were compared with Cynara cardunculus, Cynara humilis, animal rennet, a commercial plant coagulant, and fermentation-produced chymosin. Onopordum platylepis showed slower curd-firming rates than animal rennet and Cynara cardunculus, but similar behavior to Cynara humilis. Gels produced with Onopordum platylepis exhibited firmness comparable to commercial plant coagulants. The water-holding capacity was similar to other coagulants, though protein losses were higher for Onopordum platylepis, Cynara humilis, and Cynara cardunculus than animal rennet. Overall, Onopordum platylepis demonstrates potential for ewe’s milk cheese production, in which highly proteolytic coagulants are used.