Published online by Cambridge University Press: 01 June 2009
1. Acetylmethylcarbinol in cream is partly destroyed by neutralization and pasteurization, but the diacetyl content is practically unchanged.
2. Diacetyl and carbinol are retained in butter with the butter-milk fraction.
3. Diacetyl is present in butter: (a) sweet-cream 0·05 p.p.m., (b) “mild starter” 0·3–0·4 p.p.m., and (c) “high acid” 1·5 p.p.m. The diacetyl content remains fairly constant during 3½ months' storage at 14° F.
4. Diacetyl in butter does not affect the keeping quality or vitamin A content.
5. The diacetyl content tends to increase when butter is held at 40° F. for several days after manufacture. The change is not caused by oxidation with air, but is probably due to dehydrogenase activity of the “starter” organisms or their enzymes.
6. Experiments with butter “starters” are described.