The Vitamin A Potency of Creamery Butter Produced in Minnesota

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Abstract
A survey, made to determine the extent to which Minnesota butter may be relied upon as a source of Vitamin A, involved detn. of seasonal fluctuations and geographical differences in potency throughout 1943 and the first 6 months of 1944. Carotene was detd. colorimetrically and vitamin A by the Carr-Price reaction. For 1,019 samples analyzed in 1943, carotene and vitamin A averaged, respectively, 6.21 [plus or minus] 0.03 and 3.68 [plus or minus] 0.04 y/g. The means weighted by regional and seasonal butter production were, respectively, 6.14 and 3.71 [gamma]/g., corresponding to 13,958 I.U./lb. if vitamin A itself is assigned a potency of 4.00 I.U./[gamma]. With a few exceptions the butters of the state were rather uniform in potency in any given season, but marked seasonal fluctuations occurred. The winter level was 9,000-10,000 I.U./lb.; the summer level 16,500-18,500 I.U./lb. Carotene accounted for 11 to 15% of the potency of winter butter and for 21 to 25% of that of summer butter. Seasonal changes in carotene content tended to lag behind those in vitamin A. Approx. 90% of the butter produced in 1943 had vitamin A potencies over 9,000 I.U./lb.; 45% exceeded 15,000 I.U./lb. No evidence was found of loss of vitamin A potency by butter during storage.