Direct and reliable spectrophotometric method for assaying total carotenes (TC) in margarines with the minimum of sample manipulation is proposed. For the first time saponification step used in determination of carotenes in margarines was omitted leading to a substantial cost saving and reduction of time needed to complete the analysis. The resulting analytical procedure is characterized in details in terms of the figures of merit. The method is sensitive, precise and accurate; for both, standard additions and calibration in soybean oil, recovery ranges between 98 and 102%. For the most accurate analyses the approach of standard additions is preferred but for quick routine analyses this latter can be replaced by the calibration in soybean oil. Limit of detection value (LOD = 3S.D.B/a, where S.D.B is the standard deviation of the blank, "a" is the slope of calibration line) as low as 12 g TC/100 g was achieved in soybean oil enabling the sensitive detection. Concentration of TC in margarines declared as being coloured with ß-carotene (carotene) ranges between 0.3 and 0.9 mg/100 g while in carrot extract-coloured margarine TC is 0.2 mg/100 g.
- liquid-chromatographic method
- geometric isomers