Cardoon flower extract optimization: effects of formulation and preservation

The pistils of Cynara cardunculus L. flowers have long been used as natural coagulants in Portuguese and Spanish cheesemaking, particularly in protected designation of origin cheeses. Despite its historical relevance, standardized purified formulations are still unavailable, leading producers to rely on artisanal methods that result in variability in extract composition and cheese quality. This study evaluates the effect of extraction formulation and storage conditions on the technological and microbiological properties of cardoon flower extracts. A preliminary trial identified effective NaCl concentrations, guiding the selection of 5% and 20% (w/v) solutions. In the main trial, extracts were prepared using maceration and filtration with four solutions: 5% and 20% (w/v) NaCl, acetate buffer (pH 5.5) and citrate buffer (pH 3.0), stored at 4 °C for 135 days with 2% potassium sorbate. Technological properties and microbial characteristics were monitored throughout a 135-day storage period. Citrate buffer extracts showed higher enzymatic stability and microbial control, while the 5% NaCl formulation was associated with favourable technological performance indicators, including higher curd firmness and consistent milk-clotting activity. These results support the use of 5% NaCl extracts as a promising plant-based coagulant, offering a balanced solution for enzymatic efficiency and preservation in cheese production.