Application of the Phosphatase Test to Creamery Butter

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Abstract
Expts. on sour cream adjusted to conventional churning acidities and "flashed" at different temps. indicated that 185[degree] F or higher will give neg. phosphatase reactions upon samples treated by a modification of the Scharer short method as well as by the Kay and Graham 24-hr. incubation method. "Flashing" cream at 180[degree] F, however, gave neg. results by the modified Scharer short method as well as by the 21/2-hr. and 8-hr. incubation methods of Kay and Graham, although doubtful results were obtained by using the 24-hr. incubation period. Cream "flashed" at 175[degree] F gave doubtful results by the modified Scharer short method and pos. results with the Kay and Graham methods; "flashing" below 175[degree] gave pos. results with all methods. Butter freshly made from sour cream of adjusted acidity which had been "flashed" at 185[degree] F or higher gave neg. phosphatase tests when the modified Scharer short method and the Kay and Graham 24-hr. technique were used. Some indications of possible phenol production by bacterial activity in butter samples subjected to the keeping quality test of holding at 70[degree] F for 8 days (100% humidity) have been observed. Owing to factors which may stimulate phenol production in butter subjected to normal changes in temps. and environment, during the interim between its manufacture and consumption, caution should be exercised in interpreting a pos. phosphatase test as indicative of the inadequate pasteurization of the cream used in its manufacture.

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