Comparison of plant and animal rennets in terms of microbiological, chemical, and proteolysis characteristics of ovine cheese.

摘要

16 cheeses manufactured from ewe raw milk using crude aqueous extracts of flowers of (i) Cynara cardunculus as coagulant were compared with 16 control cheeses manufactured using (ii) a commercial animal rennet. Changes in the microbiological, chemical and biochemical characteristics during ripening were studied in order to determine the level of primary proteolysis in (i). The type of coagulant used had no significant effect on cheese composition (e.g. moisture, fat, protein and salt) and pH duringripening, but lower microbiological counts of Enterobacter, lactococci and lactobacilli were obtained for cheese manufactured using (i) during the first 28 days of ripening. Conversely, several biochemical differences in the cheeses were apparent as ripening progressed. Electrophoretic analyses of the water-insoluble fractions from cheeses manufactured with (i) or (ii) showed that beta-caseins were less susceptible to proteolysis than alphas-caseins and that (ii) was more proteolytic towards beta- andalphas-caseins than (i). Cheeses manufactured using (i) had higher levels of water-soluble N:total N than those manufactured using (ii), although the former showed lower levels of trichloroacetic acid-soluble N:total N and lower levels of phosphotungsticacid-soluble N:total N. The peptide profiles of water-soluble extracts of the cheeses obtained by reversed-phase HPLC showed different patterns at all stages of ripening for (i) and (ii), thus conveying important qualitative information for fundamentaldifferentiation of proteolysis by the 2 coagulants.