Abstract
Summary: Dry butterfat occasionally develops a greenish colour when stored for at least 1½ years at −12°C whereas samples of the same fat kept for 2 years at +2 or +15°C do not show this colour defect. Spectrophotometrical measurements have shown that the defect is accompanied by a chemical change of the carotene. Its absorption maxima are shifted towards the shorter wavelengths, and a new absorption is observed at 400–410, 430–435 and 450–460 mm. The possible involvement of oxidation products of carotene, such as isomeric diepoxides or furanoid oxides is discussed. The colour defect can be observed before any change in flavour is noticed.

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