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Interpretation of various assays for vitamin a in margarine
Author(s) -
Lehman Robert W.
Publication year - 1962
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02637669
Subject(s) - colorimetry , vitamin , potency , chemistry , chromatography , molar absorptivity , bioassay , spectrophotometry , food science , biochemistry , biology , in vitro , genetics , physics , optics
When margarine is fortified with all‐ trans vitamin A the assay result, whether obtained by colorimetry or spectrophotometry, should be the same as the biological potency. This paper reports the effects to be expected on each method of assay by some commercial sources of vitamin A that contain cis ‐isomers. In most cases the biological potencies are less than the potencies predicted by physicochemical procedures. Methods are presented to calculate the extent of assay differences introduced by these cis ‐isomers. Different commercial sources of vitamin A, in an amount required for 15,000 舠biological舡 units, would give values ranging from 15,200 to 20,800 units by 舠blue‐color舡 assay, from 15,100 to 19,000 units by uncorrected extinction coefficient, and from 15,000 to 18,000 units by the USP XVI assay.