Determination of folates contents in foods using microbiological assay

BASSETT, M.N., SAMMAN, N.

Granada, España

Congreso; 2nd International EuroFIR Congress. Role of food composition data in improving quality, healthiness and safety of European diets.; 2007

EuroFIR

Folate is a water-soluble vitamin that exists naturally in foods, usually in the polyglutamyl forms. The best sources, from the standpoint of amount and avaibility, are liver, fortified breakfast cereals and other grain products, legumes and vegetables in general. Food processing and preparation can destroy 50 to 90% of the folate in food. Folate is extremely susceptible to destoy by heat, oxidation and UV light. Adequate intake of folate reduced the risk of abnormalities in the early embryonic brain development and, especifically, the risk of malformations of the embryonic brain/spinal cord, collectively refered to as neural tube defects (NTDs). Determining folate intake is difficult because existing folate data in food-composition tables are scarce and unreliable. This study aimed determinate folates in foods using microbiological assay with Lactobacillus rhamnosus (formerly Lactobacillus casei) as the test organism. This assay is the most widely used method and provides a total folate value of a food. The effect of conjugate type and extraction buffer on the total of folate content of strawberry was also investigated. In the test sample, strawberry, deconjugation with rat plasma gave slightly higher, but estadistically no different folate values compared to human plasma. Was prepared standard (solution 2ng/ml of AF Sigma P7876) concentration response-curve by plotting %T readings for each level of standard solution used against amount of reference standard contained in respective tubes. Was determinate amount of AF for each level of assay solution by interpolation from standard curve. We analyze 12 of the most important foods that contribute to folate intake: brocoli, spinach, potato, lentil, soy (raw and boiling); eggs and yolks (raw, boiling and frying); beef liver (raw and rostizaded); strawberry (raw and jewels); royal jelly and avocate (raw); flour and bread. Large losses of naturally occurring of folate can occur during food processing and/or home preparation by oxidation, leaching, or both. For all foods selected, the results were agruped in a) high folate contents: yolks, spinach, eggs, soy, potato, avocate and strawberry (354,13±1,24 y 84,25±0,35mcg/100g) b) average folate contents: lentils, flour, bread and onions (83,2±1,98 a 11,6±0,1mcg/100g) and c) low folate content: broccoli, royal jelly and beef liver (56,25±3,18mcg/100g, 32±2,46 y 198,38±20,88). Conclusions: contents and losses of folates vary widely according to cooking method and type of food.