Population Levels, Species, and Characteristics of Micrococcaceae during the Manufacturing and Ripening of Armada-Sobado Hard Goat's Milk Cheese

Abstract

The changes in the counts and the species of Micrococcaceae were studied throughout the manufacturing and ripening of a Spanish hard goat's milk cheese, the Armada-Sobado variety. In the milk, counts on mannitol salt agar (MSA) ranged from 2 × 104 to 5 × 104 CFU/g. These counts showed the maximum value in the curd (7 × 104 to 4 × 105 CFU/g), decreasing afterwards slowly but steadily throughout the ripening process to reach final counts on average 2 logarithmic units lower than those found in the curd. Of 280 isolates obtained from MSA during manufacturing and ripening, 66 (24%) were considered to be Micrococcaceae. Staphylococcus sciuri (22.5% of the isolates at this sampling point) and Staphylococcus saprophyticus (7.5%) were the only two species of staphylococci isolated from the milk. In the curd, S. sciuri increased its proportion (30%) whilst the percentage of S. saprophyticus remained constant. None of these species was isolated from the cheese. S. aureus was detected only in curd (7.5% of the isolates obtained at this sampling point). S. xylosus, S. capitis, S. epidermidis, and S. warneri were isolated from curd and cheese, or exclusively from cheese, but always in very low proportions. Micrococcus varians (10%) and M. roseus (5%) were the two species of micrococci isolated from the milk. M. varians increased its proportion in curd (17.5%) and could not be isolated in cheese. M. roseus appeared neither in curd nor in cheese. All the isolated staphylococcal strains were tested for production of A, B, C, and D enterotoxins. The three isolated strains of Staphylococcus aureus produced A and C enterotoxins, but neither B or D. Of 41 coagulase-negative strains only two of the Staphylococcus sciuri isolated from milk produced C enterotoxins.