Chill in ice water bath 5 min. Centrifuge 5 min at 2400 x g . Read absorbance of butanol extracts with spectrophotometer at 650 nm. If less than zero, record as zero. Any sample exceeding the levels listed in Table 1 is violative.
Different cheeses have different levels.
The value per gram of cheese is obtained by multiplying the value listed in the CFR by 4. Official Methods of Analysis, 15th ed. Fanni, J.A. 1983. Phosphohydrolase activities of Penicillium caseicolum . Hammer, B.W., and H.C. Olson. 1941.