Time and temperature of refrigeration affect the coagulation properties of the milk for the production of raw ewe’s milk cheese

Resumo

This work investigated the effect of refrigeration on the microbiological and the coagulation properties of raw ewe’s milk from Azeitão PDO cheese region. Rennet and Cynara cardunculus were used as coagulants. No significant changes were detected in the milk clotting properties until milk pH has significantly decreased. The coagulation with C. cardunculus showed higher sensitivity to the refrigeration time and temperature. Microbial counts, at 8 °C, reached 6 log cfu/mL after 48h of refrigeration; apparently psychrotrophs accounted for the majority of total microbial counts. After three days at this temperature the milk pH values were unappropriated for cheesemaking. This work highlight the importance of microbial growth in raw milk rather than the effect of refrigeration itself and the need of stricter requirements of hygiene during milking, and also the need of the inclusion of psychrotrophic counts in the evaluation of raw ewe’s milk quality for cheesemaking. The refrigeration of the milk should be preferably made at no more than 4 ºC, and for no longer than 24 h.