485. The effect of temperature on the development of broken cream

Abstract

Three strains ofB. cereuswere grown in milk at nine different temperature combinations. Broken cream could be prevented by holding milk at 5° C. or lower for 24 hr. before transferring to 15 or 18° C. for a further 24 hr., but with a subsequent period of storage at 22° C. the fault was not prevented. Broken cream developed after storage at 10° C. followed by 18 and 22° C., but not in milk kept at 10° C. and then transferred to 15° C. After preliminary storage at 15° C. the fault appeared within a further 24 hr. regardless of the subsequent storage temperature.With two strains ofB. cereusit was observed that pasteurization accelerated spore germination and hence the development of the fault. With low levels of inoculum there was delay in the appearance of the fault with one strain of the organism.In twenty-four samples of commerically pasteurized milk it was shown that the fault could be controlled by refrigeration at 5° C. before distribution except when the subsequent temperature was allowed to rise to 22° C.Contrary to the suggestion made by Davis (15) preliminary observations indicate that the growth ofB. cereusand the development of broken cream is not inhibited by the presence of acid-producing organisms such asStr. lactis.