J. C. Bauernfeind

Provitamin a activity and stability of β-carotene in margarine

SummarySamples of synthetic β-carotene have been assayed for vitamin A activity by the rat-curative, growth method against vitamin A acetate and compared with natural carotene. The U.S.P. XIV diet was modified by the addition of vitamin B12 and α-tocopherol, which have been reported to enhance carotene utilization. Doses of vitamin A and carotene were given in cottonseed oil and in margarine; but, contrary to the report of Deuelet al. (13), no significant increase was observed in the utilization of carotene fed in margarine. The samples tested include crystalline all-trans β-carotene, micropulverized all-trans β-carotene in an oil suspension, and a series of 10 commercial margarines fortified with vitamin A. and carotene in a ratio of about 2 I.U. of vitamin A to 1 I.U. of carotene.In terms of vitamin A activity in the rat bioassay, the average potency of β-carotene in three separate bioassays of crystalline carotene was found to be 1,730,000 I.U. per gram with a standard error of ±3.5%. Thus in these assays 1 I.U. of vitamin A activity was found to be equivalent to 0.58 mcg. of all-trans β-carotene, a value in essential agreement with 0.6 mcg., the presently accepted International Standard. For margarine samples containing vitamin A and β-carotene, the average vitamin A activity in 2 bioassays was found to be very close to that calculated from the colorimetric assays, using the factor for β-carotene, 0.6 mcg.=1 I.U. The fact that other workers have reported higher provitamin A activity for β-carotene in the rat bioassay indicates the dependence of the results on the particular conditions of the bioassay.The stability of vitamin A and β-carotene in commercially prepared margarines stored at 40°F. and 75°F. was studied by accepted colorimetric procedures. Average retention values of 94% or better were obtained in margarines stored two months when the vitamin activity was supplied either from β-carotene or from vitamin A.