Growth of Staphylococcus aureus and enterotoxin a production in foods containing polyphosphates
1990
Shelef, L.A. | Wang, Z.L. | Udeogu, A.C.
Effects of pyro-, tripoly- and hexametaphosphates (0.5 and 1%, w/w) on growth of Staphylococcus aureus strain 196E and enterotoxin A (SEA) production were studied in cooked custard and beef at 22 degrees and 30 degrees C. No effect was observed in custard, where cell numbers/g increased from 10(3) to 10(8) and SEA reached 4.2 ng/g after 48 h at 22 degrees C, irrespective of treatment. Cell numbers in cooked beef were ca. 10(9)/g after 48 h, and reduced numbers (by 1.5-2 log cycles) were found in samples containing 0.5 and 1% pyrophosphate during incubation at 22%, but not at 30 degrees C. SEA concentrations in beef were 28 ng/g after 48 h at 22 degrees C, and 93 and 184 ng/g after 24 and 48 h, respectively, at 30 degrees C. SEA concentration correlated with amount of growth, and was nondetectable when cell numbers were less than or equal to 10(6)/g. Reduction of the meat pH by sodium acid pyrophosphate contributed to the observed inhibitory effect.
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