Novel milk-clotting enzyme from sour orange flowers (Citrus aurantium L.) as a coagulant in Iranian white cheese

The aim of this work was to evaluate the partially purified protease of sour orange flower extract (OFR) by determining the protein profile and milk-clotting activity as well as chemical and sensory characteristics of cheese throughout 45 days of ripening. Three rennets were used to produce cheeses, (1) the sour orange flower rennet at a level of 0.2 g/L milk (OFR), (2) standard calf rennet at a level of 0.02 g/L milk (CR), and (3) OFR (0.1 g/L)/CR (0.01 g/L). OFR cheese acidity was higher compared to that of the calf rennet (CR) and OFR/CR (50:50) samples. Significantly (p < 0.05) higher proteolytic activity was observed in OFR cheese through measuring the soluble nitrogen (SN), non-protein nitrogen (NPN), and total free amino acids (FAA) content. Protein profiles of cheeses determined with SDS-PAGE also confirmed higher levels of casein hydrolysis in OFR cheese. Reversed-phase high-performance liquid chromatography revealed the noticeable qualitative and quantitative differences between peptide profiles of all treatments. Higher casein degradation and production of peptide plus amino acids in OFR and OFR/CR cheeses suggested faster and more intensive ripening. The flavor and texture acceptance scores were reduced on the last day of storage in OFR cheese, while OFR/CR cheese received the highest score for flavor. In conclusion, the blend of OFR/CR may be regarded as an alternative for calf rennet in white brined cheese production which accelerates ripening process and causes development of a unique flavor in the final product.