Folatos in vegetables - influence of the type culture and processing. / Folatos em vegetais - influencia do tipo de cultivo e do processamento.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Despite the recent discoveries about the possible beneficial actions of folates to human health, data on the real contents of this vitamin in Brazilian foods, are little, ever for vegetables, considered the main source of this nutrient. Scarcer still are studies on the stability of folates after domestic cooking and industrial food processing. Considering that the concentration of folates in foods is somewhat dependent on the soil/climate conditions, it becomes important to evaluate this vitamin in Brazilian vegetables, in order to guarantee the ingestion of folates by the population. Thus the main of this study was to contribute to the knowledge of folates in foods. Folates were determined by high performance liquid chromatography technique. The method was validated and applied to samples of spinach, broccoli, tomatoes, ketchup, sauce and tomato juice. Small adaptations in the methodology were made for the extraction step of the samples and others in the chromatographic separation system. In general, the validation parameters established for the products analyzed were of 94% for recovery, variation coefficient below 1.4% in the repeatability assays and detection limits of 5, 30, 30, 7pg/mL and 5ng/mL 5-methyl-tetrahydrofolate (5-methylTHF), 5-formyl-tetrahydrofolate (5-formylTHF), 10-formyl- tetrahydrofolate (10-formylTHF), tetrahydrofolate (THF) and 10-methyl- tetrahydrofolate (10-methylTHF), respectively. For tomatoe and tomato products the only folate form was 5-methylTHF. There was no significant difference between the contents of this form of the vitamin found in tomatoes cultivated by the traditional (176,0 to 326,9µg/100g) and the organic method (208.7 to 345.1µg/100g) form. For tomatoe products, both, brands and batches showed significant differences in the concentration of 5-methylTHF. For ketchup, sauce and tomato juice the values were from 58.8 to 265.9µg/100g, 103.9 to 325.0µg/100g and 138.9 to 330.8µg/100g, respectively. Thus, tomatoes and tomato products can be considered as folates sources. In broccolis, in addition to 5-methylTHF, 5-formylTHF was also detected. In this case, these was a significant difference in the contents of 5-methylTHF for the organic (954.0 to 1740.0µg/100g for 5-methylTHF and 7.9 to 13.6µg/100g for 5-formylTHF) and traditional (414.0 to 742.0µg/100g for 5-methylTHF and 4.8 to 12.8µg/100g for 5-formylTHF) cultivation, the organic form presenting higher concentrations. For 5-formylTHF there was not significant difference. It was also noted, that when the broccoli was cooked in water, the losses were of approximately 85%, that most of the vitamin (70%) being founder the cooking water, indicating that the leaching process is responsible for the greater losses of folates. For the spinach the same folates forms were found as in broccolis (5-methylTHF and 5-formylTHF). For both, broccoli and spinach, 5-methyllTHF corresponds to approximately 99% of the folates contents. For spinach there was no significant difference in the folates contents for traditional (386.0 to 550.4µg/100g for 5-methylTHF and 4.0 to 6.3µg/100g for 5-formylTHF) and organic (295.3 to 599.9µg/100g for 5-methylTHF and 5.0 to 7.7µg/100g for 5-formylTHF) cultivation. The contents of the different folate forms, in spinach were also evaluated at different periods of the year (September to November/2002 and May to July/2003), and it was concluded there was no significant difference between the values obtained in the periods studied. Cooking in water resulted in losses of 66% for 5-methylTHF and 47% for 5-formylTHF. The determination of folates in the cooking water, confirmed that, in this case, the losses were mostly due to leaching, most of the vitamin, being found in the water. It was concluded that all the vegetables evaluated in this study could be considered important folates sources, however, the cooking in water caused enormous losses of the vitamin. It is therefore of great importance to use the cooking water so that adequate amounts of this important nutrient are ingested.

ASSUNTO(S)

folatos vegetables analysis vegetais analise cromatografica chromatography

ACESSO AO ARTIGO

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