Comparison of Plant and Animal Rennets in Terms of Microbiological, Chemical, and Proteolysis Characteristics of Ovine Cheese

Abstract

Cheeses manufactured from ovine raw milk using crude aqueous extracts of flowers of Cynara cardunculus as rennet were compared with cheeses manufactured with a commercial animal rennet. Changes in a number of microbiological, chemical, and biochemical characteristics throughout ripening were followed in attempts to get scientific insight especially into the primary proteolysis brought about by this plant rennet in cheese. Using averages and corresponding 95% confidence intervals, it was concluded that the type of rennet had no significant effect on cheese composition (e.g., moisture, fat, protein, salt, and pH at the center and at the surface) over the ripening period but lower microbiological counts of Enterobacteria, Lactococci, and Lactobacilli were obtained for cheese manufactured with plant rennet until 28 days of the ripening. Conversely, several biochemical differences in cheese became apparent as ripening progressed. Electrophoretic analyses of the water insoluble fractions from cheeses manufactured with either rennet showed that β-caseins were less susceptible to proteolysis than αs-caseins and that the animal rennet was more proteolytic on β- and αs-caseins than the plant rennet; cheeses manufactured with the plant rennet exhibited higher levels of WSN/TN than cheeses manufactured with the animal rennet, although the former showed lower levels of TCA/TN and lower levels of PTA/TN. The peptide profiles of water-soluble extracts of the cheeses obtained by reversed-phase HPLC exhibited different patterns at all stages of ripening for the two rennets utilized, thus conveying important qualitative information for fundamental differentiation of proteolysis effected by either rennet. Keywords: Rennet substitute; Cynara cardunculus; ovine cheese; ripening; proteolysis