manual of methods for determining micronutrients in fortified foods

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VI. Procedure 1. Place the filter paper over the watch glass 2. Wet the surface of the filter paper with the solution of potassium thiocyanate. Let the liquid penetrate the paper fibers. 3. Using a hand sieve, sift portion of the flour sample in order to load a thin layer over the entire wet area. Shake off or scrape off any excess flour. 4. Add a little more of the acidic solution of potassium thiocyanate over the flour layer. 5. Add small amounts of the H 2 O 2 -solution. Let it stand for a few minutes for the reaction to occur (oxidation of any form of iron to iron(III)). Red spots indicate the presence of added iron from any source. - 8 -
VII. Interpretation • Unfortified samples of wheat flour might show a reddish coloration, but not well defined red spots as shown on the picture below. • Number and density of spots might be associated to the iron level in the sample. The more red spots appear, the higher the concentration of iron in the sample. The picture below compares the number of spots in two samples with different concentrations of iron. The first sample (left) shows only a few spots indicating the iron content is low, whereas the second sample (right) shows more spots indicating the iron content is higher. • Although there is no rule for the size of the spots, the appearance of them might vary from small, well defined, to large spots tending to diffuse as iron solubilizes (see picture below). This might be due to the source and quality of iron used to fortify flour and although no conclusion can be drawn based on this, keep in mind that you might find different shapes when analyzing samples from different mills or countries. - 9 -
Page 1 and 2: MANUAL OF METHODS FOR DETERMINING M
Page 3 and 4: - 3 -
Page 5 and 6: I. Introduction Food fortification
Page 7: A. Qualitative method to determine
Page 11 and 12: − − − − − − Refrigerato
Page 13 and 14: 3. Stir with a magnetic stirrer for
Page 15 and 16: IX. Calculations 1. Plot a graph of
Page 17 and 18: − 1,10-phenanthroline-monohydrate
Page 19 and 20: . Preparation of the ash solution 1
Page 21 and 22: III. Methods to determine vitamin A
Page 23 and 24: IV. Equipment and materials − 50
Page 25 and 26: VIII. Qualitycontrol Run the flour
Page 27 and 28: − Volumetric flasks (100 and 10 m
Page 29 and 30: VII. Procedure a. Preparation of sa
Page 31 and 32: c. Clean-up and concentration proce
Page 33 and 34: VIII. Calculations Results can be c
Page 35 and 36: IV. Methods to determine water-solu
Page 37 and 38: A. Method to determine riboflavin i
Page 39 and 40: VI. Standard solutions 1. Riboflavi
Page 41 and 42: 8. Pipette exactly 4.0 mL of the fi
Page 43 and 44: B. Determination of thiamin in flou
Page 45 and 46: In a 25-mL beaker weigh 0.9602 g so
Page 47 and 48: C. Determination of niacin in flour
Page 49 and 50: 7. Transfer the extract to a 250 mL
Page 51 and 52: IV. Equipment − Analytical balanc
Page 53 and 54: 6. Ammonium hydroxide-0.1M: In a 10
Page 55 and 56: VIII. Procedure A. Strain propagati
Page 57 and 58: Note: Prior to start analyzing samp
Page 59 and 60:
IX. Calculations 1. Calculate the a
Page 61 and 62:
B. Verification 1. In an Erlenmeyer
Page 63 and 64:
V. References • Bowman BA and Rus
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manual of methods for determining micronutrients in fortified foods

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