The usual methods for provitamin A evaluation of foods convert the total pigment amount, determined spectrophotometrically, into vitamin A units. Since the totally inactive lycopene is the major carotenoid in the tomato, such readings result in erroneously high provitamin A values.
In view of the recent development of chemically bonded, reversed-phase, microparticulate packings and their use in high-performance liquid chromatography which combines highly accurate and reproducible resolution with the speed and ease of operation, a new method using such a system was developed to isolate carotenoid pigments from tomato samples. A 1%min column separation was thus achieved, dramatically decreasing the analysis tizpe of the classical open column chromategraphic procedures, which often result in unresolved and altered fractions due to long-term exposure to oxygen, light, solvents and sometimes adsorbent.
B-Carotene and lycopene were determined and quantitated in six tomato samples. P-Carotene, 100 y0 vitamin A-active, was expressed in International Units of vitamin A_ The newly developed method gives a more reliable evaluation of the fruit potency in vitamin A than the methods of the Association of Official Analytical Chemists currently used for food composition tables.