EFFECT OF LACTATION STAGE ON THE CHEESE-MAKING PROPERTIES OF MILK ANDTHE QUALITY OF SAINT-NECTAIRE-TYPE CHEESE

TWO groups of eight multiparous cows with different calving periods (N ovember or February) were managed in the same way during lactation. Du ring four 4 week experimental periods distributed over 12 months, the cows were fed on a diet composed of hay and concentrate (70:30) in a r estricted and controlled amount which varied according to their lactat ion stage, so as to cover the animals' requirements correctly. The ani mals' average lactation stage varied according to period from 26 to 29 8 d. Milk from each group was processed on two occasions during each p eriod to make Saint-Nectaire-type cheese; the cheesemaking conditions were the same throughout. Lactation stage had an important effect on m ilk fat, protein and calcium contents but not on the casein:protein ra tio or phosphorus content. The milk pH and the urea content were highe r in late lactation. The calcium concentration of milk was higher in l ate lactation but the soluble fraction was higher in early lactation. Despite higher protein contents, the maximal firmness-of thc coagulum of late-lactation milk was not different from that of early or mid-lac tation milks. pH was higher in cheeses from late-lactation milks compa red with those from early and mid-lactation milks. Cheeses from early lactation milks were more yellow than the others and had a lower dry m atter fat content. In sensory analysis the odour of cheeses from early and late-lactation milks was less pleasant than that of those from mi d-lactation milks. Cheeses from late-lactation milks were more melting and less firm than those from early or mid-lactation milks. Their tas te was mofe intense and more persistent. At tasting, they were less ap preciated than the others. These differences were linked to increased proteolysis in the cheeses made with late-lactation milks.