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The Effect of Copper upon the Activity of Bacteria Associated with Swiss Cheese Manufacture

Department of Dairy Science, University of Illinois, Urbana

ABSTRACT

Data have been presented which demonstrate that bacteria associated with Swiss cheese manufacture vary considerably in their behavior toward copper. Copper had no pronounced effect upon the growth and acid production by S. thermophilus and three species of homofermentative lactobacilli. Conversely, copper increased the lag phase and decreased the growth rate of the three P. shermanii cultures. A similar lag in volatile acid and CO2 production was observed. These effects were roughly proportional to the copper concentration in the growth medium. Although copper depressed the rate of growth, volatile acid and C02 production after 13 days were approximately equal for all levels of copper studied. Copper did not alter the ratio of acetic to propionic in the volatile acid fraction.

Preliminary evidence indicated that high levels of copper (18.0 ppm.) in Swiss-type cheese exerted an unfavorable influence on the course of ripening, whereas a normal and satisfactory ripening occurred in cheeses containing 0 to 0.5 and 7.5 to 8.0 ppm. copper.