Relation of Acid Development During Cheesemaking to Development of Staphylococcal Enterotoxin A

The examination of the nmnufacturing records of 378 vats of cheese made during the period in which 59 of those vats developed staphylococcal enterotoxin A indicated the toxic vats were subnormal in acid development. If the growth of the sta~er organisms is nornml as measured by acidity, toxin production due to the presence of contaminating staphylococci is suppressed. Acid development was considered subnormal for Cheddar cheese if the milling acid expressed as lactic acid was less than 0.40%, and subnormal for the Monterey and K_uminost, a granular, washed curdtype cheese, if the drawing acid was 0.15% or less. The milling acid of the 56 vats of toxic Cheddar cheese ranged from 0.16 to 0.35% ; 26 of these vats developed less than 0.20% milling acid. Not all of the subnormal vats of Cheddar cheese contained toxin. Eighty-seven vats of subnormal Cheddar cheese were toxin-free and 230 vats of normal acid-developed Cheddar cheese were also toxin-free. The two vats of toxic Monterey and the one vat of toxic Kuminost developed 0.11 to 0.13% drawing acid. All of the cheese was phosphatase negative, indicating postpasteurization contamination by toxin-producing organisms.