Determination of Carotene in Sweet Potatoes.

The determination of carotene in fresh plant tissue is complicated by the presence of large amounts of water. The tissue must be dehydrated before the carotenoids can be extracted with fat solvents. This has been accomplished in the past by the addition of acetone or ethanol with a fat solvent such as Skellysolve B (8, 5). These methods employ a Waring blendor for disintegrating the tissue in the presence of the extracting solvents. More recently, MITCHELL and KING (4) found that, if alfalfa and cereal grasses were first blanched or autoclaved, the water then could be removed by drying at 650 C. without causing appreciable loss of carotene. Blanching or autoclaving was necessary to prevent destruction of carotene by the enzyme lipoxidase during drying (2). After the plant tissue was dried and ground, the carotene was removed by the procedure used by SILKER, SCHRENK, and KING (6) for dehydrated alfalfa meal, which consists of allowing the sample to stand overnight in contact with 60 ml. of 30% acetone in Skellysolve B. This method was shown to reduce greatly the sampling error that is encountered with such non-uniform plant tissues as alfalfa and cereal grasses. In view of the advantages previously reported for the method, and in anticipation of the routine determination in this laboratory of the carotene content of a large number of sweet potato samples, it was desirable to determine if the method proposed by Mitchell and King could be used with the sweet potato. This is a report of the results obtained.