engleski

New simple spectrophotometric assay of total carotenoids in margarines

Carotenoids are used as colorants (E160a, E160b) in margarines. Palm oil used in manufacturing of margarine contributes to the content of total carotenoids (TC) as well. New spectrophotometric method is proposed for determination of TC in commercial margarines and preliminary data presented. Margarines were thoroughly homogenized, kept at +4 oC and equilibrated at RT before use. An accurately weighted amount of margarine (pure or after addition of Betatene® ; ) was dissolved in 10- to 20-fold volume excess of n-hexane (p.a.). The mixture, shaken mechanically for 15 min with the formation of yellowish suspension, . was centrifuged at 3000 rpm for 10 min. Quantitative extraction of carotenoids was achieved and the interferences of norbixin and curcumin obviated. All sample manipulations were performed under the from-light-protected conditions. The upper, clear, yellowish, hexane layer and the lower, turbid colorless aqueous layer separated with a white precipitate remaining at the interface. The hexane layer was collected to record spectrum ; the value of Amax at 440-450 nm served for the calculation purposes. The method of standard additions was used (Fig. 1). Fourteen margarines purchased in supermarkets in different European countries were analyzed. They contained 38-80% total fats and oils (ratio saturated/unsaturated fatty acids 1:2 or 1:3). The concentration of TC, expressed as total carotenes, ranged between 0.1 and 0.9 mg/100 g margarine for the samples declared as coloured by carotenes, and 0.1 to 0.2 mg/100 g in those coloured by annatto dye-stuffs. Full validation of the new method is currently underway.

carotenoids; assaying; margarines; spectrophotometry

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