Vitamin C Investigation

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Kieron McKeigue        

Individual Investigation

Hypothesis: Fresh orange juice has a higher vitamin C content than orange juice made from concentrate.

Background

Concentration, in biochemistry terms, is “increasing the strength or proportion of (a substance or solution) by removing or reducing the water or any other diluting agent or by selective accumulation of atoms or molecules.” (Oxford English Dictionary). Therefore concentrated fruit juice has had its water removed (probably for ease of transportation) then had water re-added (reconstituted) before packaging.

Vitamin C is an important part of the human diet. It is found in fruits, green vegetables and potatoes, and is “necessary for the formation of blood and bone and for resistance to infection.” (Ramsden, 1995). It is an antioxidant which is capable of counteracting the damaging effects of oxidation. Vitamin C helps to prevent deficiency diseases, in particular scurvy, and is abundant in citrus fruits such as lemons, limes and oranges. Its chemical name, ascorbic acid, “is derived from a- and scorbuticus (Scurvy) as a shortage of this molecule may lead to scurvy.” ().

The amount of vitamin C in a fruit juice can be estimated using a blue chemical die called DCPIP (common name 2,6-dichlorophenolindolephenol). It is reduced by an equal amount of vitamin C to a colourless, or sometimes pink, compound solution.

This experiment will aim to find out whether fresh orange juice really does contain more vitamin C than those made from concentrate. By first testing a known concentration of vitamin C solution it should be possible to calculate the vitamin C content in each fruit juice.

Method

Apparatus: Safety eye mask, lab coat, ascorbic acid solution 0.1%, DCPIP solution 0.1%, test tube holder, 21 test tubes (3 for standardisation test, 12 for juices from concentrate and 12 for fresh orange juices), pipette for measuring DCPIP solution, 2 x syringes (1 for measuring ascorbic acid and 1 to measure orange juice with), 3 brands of orange juice from concentrate, 3 brands of fresh orange juice, paper, pencil.

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Take 3 of the test tubes, label them 1 to 3 and place them in the test tube holder. Use the pipette to put 1 ml DCPIP solution in each test tube. Using the syringe, drop 0.1ml ascorbic acid solution (vit C) into test tube 1, then gently shake the test tube. Repeat, adding 0.1ml vit C solution and gently shaking until the DCPIP solution is decolourised. Note the amount of vit C solution used to fully decolourise the DCPIP solution. Repeat the test for test tubes 2 and 3, noting how much vit C solution is required.

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