RESUMEN
Latin America has a wide variety of carotenogenic foods, notable for the diversity and high levels of carotenoids. A part of this natural wealth has been analyzed. Carrot, red palm oil and some cultivars of squash and pumpkin are sources of both beta-carotene and alpha-carotene. beta-carotene is the principal carotenoid of the palm fruits burití, tucumã and bocaiuva, other fruits such as loquat, marolo and West Indian cherry, and sweet potato. Buriti also has high amounts of alpha-carotene and gamma-carotene. beta-Cryptoxanthin is the major carotenoid in caja, nectarine, orange-fleshed papaya, orange, peach, tangerine and the tree tomato. Lycopene predominates in tomato, red-fleshed papaya, guava, pitanga and watermelon. Pitanga also has substantial amounts of beta-cryptoxanthin, gamma-carotene and rubixanthin. Zeaxanthin, principal carotenoid of corn, is also predominant only in piquí. delta-Carotene is the main carotenoid of the peach palm and zeta-carotene of passion fruit. Lutein and beta-carotene, in high concentrations, are encountered in the numerous leafy vegetables of the region, as well as in other green vegetables and in some varieties of squash and pumpkin. Violaxanthin is the principal carotenoid of mango and mamey and is also found in appreciable amounts in green vegetables. Quantitative, in some cases also qualitative, differences exist among cultivars of the same food. Generally, carotenoids are in greater concentrations in the peel than in the pulp, increase considerably during ripening and are in higher levels in foods produced in hot places. Other Latin America indigenous carotenogenic foods must be investigated before they are supplanted by introduced crops, which are often poorer sources of carotenoids.
Asunto(s)
Carotenoides/análisis , Frutas/química , Verduras/química , Brasil , Manipulación de Alimentos , América Latina , Aceites de Plantas/análisis , beta Caroteno/análisisRESUMEN
The difficulties inherent to provitamin A determination and the present state of development of the analytical methodologies are appraised. The procedures, the advantages and disadvantages and the possible sources of error of the methods involved are discussed. Open-column methods are still the most viable option in developing countries but the efficiency and reproducibility of the chromatographic separation depend largely on the analysts skill and experience. Although HPLC chromatograms are highly reproducible, the problem is to transform the peak areas to provitamin A concentrations because of the instability, varying purity and unavailability of provitamin standards. Internal standardization with the stable Sudan appears to be a promising solution. Separation of cis-isomers requires rechromatography in open-column systems. For HPLC, this problem still remains to be solved. Confirmation of the identity of the provitamins and prevention of degradation during the analysis are also dealt with. Notwithstanding the obstacles involved, reliable data can be obtained with adequate application of the analytical techniques and proper interpretation of the results.
Asunto(s)
Carotenoides/análisis , Análisis de los Alimentos/métodos , Vitamina A , Artefactos , Biotransformación , Carotenoides/clasificación , Cromatografía Líquida de Alta Presión , Extractos Vegetales/química , Plantas Comestibles/química , Estándares de Referencia , Reproducibilidad de los Resultados , EspectrofotometríaRESUMEN
To answer the need for simple, economical, rapid methods for mycotoxins, a procedure for screening and quantitation of ochratoxin A was developed. A methanol-aqueous KCl extraction is used, followed by cleanup with clarifying agents and partition into chloroform. Part of the chloroform extract is used for screening and the other part for quantitation by thin layer chromatography (TLC). The screening procedure takes 40 min, using a silica gel/aluminum oxide minicolumn developed for this purpose. The limits of detection are 80 and 10 micrograms/kg, respectively, for minicolumn screening and TLC quantitation. Ammonium sulfate is efficient in cleaning samples of corn and cassava; cupric sulfate is better with peanuts, beans, and rice. Tests were conducted on triplicate spiked samples of yellow corn meal, raw peanuts, dried black beans, polished rice, and cassava flour at different levels (400, 200, 80, 40, and 10 micrograms/kg). Recoveries ranged from 86 to 160% and the coefficients of variation ranged from 0 to 26%.