Data Sheet: Activity - Micronutrients

  Procedure I - Vitamin C Testing via Redox Titration In the table below indicate the number of drops needed for each sample juice to change color. Table I. Number of Drops for Color Change Drops Needed for Sample A Drops Needed for Sample B Drops Needed for Sample C Drops Needed for Sample D Drops Needed for Sample E Observations and Questions [1] List the juice samples (A-E) from lowest vitamin C content to highest vitamin C content. Label the lowest and highest.     [2] For the ranks you listed in [1] above, explain how you made the decision about vitamin C content for those samples. That is, what data evidence did you use from this laboratory activity as part of your decision-making process? How did your data help you decide the rank?   [3] In your own words and in general terms, explain how the color change relates to the reaction between vitamin C and molecules in the solution containing the indicator substance. What is the significance of the color change?     [4] Refer to your results in Table I. What accounts for the difference in the number drops needed for the color change to occur?   [5] Assume that Procedure I used 100 g of juice for each of the sample juices. If each drop of test solution corresponds to 10 mg of vitamin C per 100 g of juice, then how many mg of vitamin C are in one serving (250 g) of each of the sample juices? Show your calculation. Formula: Vitamin C in one serving = 250 g × (10 mg Vitamin C / 100 g) × (number of drops) Sample A Calculation: Sample B Calculation: Sample C Calculation: Sample D Calculation: Sample E Calculation: [6] Refer to question [5] and review the Background reading to explain the rationale for making an equivalence between each drop of the test solution and 10mg vitamin C per 100 grams of juice in a serving of each sample of juice.   [7] If you can have only one 250 g serving each day, which sample juices meet (or exceed) the RDA (75-90 mg/day) for vitamin C? Explain your reasoning. Show relevant calculations.     Procedure II - Colorimetric Iron Testing In the table below indicate the color intensity (1-5) of each sample juice after a drop of test solution has been added. Note: color intensity (saturation) scale: 1 = lowest intensity, 5 = highest intensity. See the example scale in Background section as a reference.   Table II. Color Intensity Value Sample A Sample B Sample C Sample D Sample E Observations and Questions [8] List the juice samples (A-E) from lowest iron content to highest iron content. Label the lowest and highest.   [9] For the ranks you listed in [8] above, explain how you made the decision about iron content for those samples. That is, what data evidence did you use from this laboratory activity as part of your decision-making process? How did your data help you decide the rank?   [10] Based on your experimental results, which one of the juice samples is a poor source of iron? Which sample juice appears to be the best source of iron? If you have iron deficiency anemia, then which sample juice is the better choice for you?   [11] Refer to your results in Table II. What accounts for the difference in the color intensity across the sample juices?   [12] Women of child-bearing age need to intake 2-3 times more iron in their diets than other adults. Discuss how adding more citrus fruits into their diets can help raise their iron levels.