The effects of boiling and freezing on the Vitamin C concentration

By Bobby Ward,2014-05-21 22:20
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The effects of boiling and freezing on the Vitamin C concentration

    The effects of boiling and freezing on the Vitamin C

    concentration in spinach

    F.J. Smolders & C.K. Jansen

    Gymnasium Felisenum, The Netherlands


    Vegetables are edible parts of plants and are usually eaten as main meals and snacks. They contain many things necessary for a healthy diet and must be eaten many times a week. One of the healthiest vegetables around is spinach. Spinach contains Vitamins A, C and K, minerals like calcium and magnesium, fibers, folic acid and β-Carotene. Spinach helps

    preventing cardiovascular diseases, strokes, overweight, cancer and osteoporosis. It is said that a vegetable is healthier when its fresh. Many people boil their vegetables before eating them, a process that destroys a lot of Vitamin C. If you want to preserve your food, freezing is a commonly used method. This could however, effect the Vitamin-C concentration. We wanted to test this. We took some fresh spinach and divided it into three groups. The first group was left untouched, the second group was boiled and the third group was frozen. We then measured the amount of Vitamin C in these three groups by titrating with 2,6-dichlorophenolindophenol. We think both boiling and freezing will lower the Vitamin C-concentration and we also expect to see a bigger decrease through boiling because the high temperature will destroy the Vitamin C.


    Spinach (Spinacia oleracea) is a flowering

    plant in the family of Amaranthaceae. It is

    native to central and south-western Asia. It

    is an annual plant (rarely biennial), which

    grows to a height of up to 30 cm. Spinach

    may survive over winter in temperate

    regions. The leaves are alternate, simple,

    ovate to triangular-based, very variable in

    size from about 2-30 cm long and 1-15 cm

    broad, with larger leaves at the base of the

    plant and small leaves higher on the

    flowering stem. The flowers are

    inconspicuous, yellow-green, 3-4 mm

    diameter, maturing into a small hard dry

    lumpy fruit cluster 5-10 mm across

    containing several seeds.

     Vitamin C or ascorbic acid is an essential

    nutrient for humans and many animals. Figure 1: Spinach

    The pharmacophore of vitamin C is the

     ascorbate ion.


    In living organisms, ascorbate is an anti-This method was repeated three times for oxidant, since it protects the body against the 75g of spinach that was left. oxidative stress, and is a cofactor in several A burette was filled with DCPIP and the vital enzymatic reactions. four residues were titrated. Because DCPIP

     Vitamin C react 1:1, the amount mol and2,6-dichlorophenolindophenol or DCPIP DCPIP used to titrate the residue is equal is a blue chemical compound used as a to the amount mol Vitamin C in the residue. redox dye. Oxidized DCPIP is blue, reduced DCPIP is colorless. 2.

    Some fresh spinach was put in a freezer DCPIP and Vitamin C react 1:1, so when,

    until it was completely frozen. after titration, one mol of DCPIP was

    The exact same method as described in test needed to turn the Vitamin C solution red,

    was then used to determine the amount of one mol of Vitamin C was in the solution.

    Vitamin C in the residue.

    This method will be used to measure the

    amount of Vitamin C in our three groups 3.

    of spinach. Once again 100g of spinach was weighted

    and divided it into 4 portions of 25g. One Our research question is: how big is the portion of 25g. was put in a volumetric effect of boiling and freezing on the flask and some water was added. The Vitamin C concentration of spinach? water + spinach was then boiled for 15

    minutes and filtered it when it was done. Out hypothesis is that both processes will

    This was repeated three times for the 75g have a big effect on the Vitamin C

    that was left. The method as described in concentration, boiling having the largest

    test 1. was then repeated again by grinding, effect.

    filtering and then titrating the spinach. Experimental Design

    The experiment was split up into three There also were a few variables we needed parts: to take into account:

    1. Normal Spinach

    2. Frozen Spinach Independent Variable: The state the

    3. Boiled Spinach spinach was in (normal, boiled, frozen) 1.

    100g of spinach was weighted and divided Dependant Variable: The amount of

    it into 4 x 25g. DCPIP needed for titration. One portion of 25g was then put into a

    mortar and some sand and 25ml of acetic Control Variables: Type of spinach,

    acid was added. These materials were boiling time, amount of water used for grinded until nothing but fluid was left. boiling, room temperature, amount of The fluid was filtered using some filter acetic acid added, amount of sand added, paper and a funnel. 10ml of the residue filtrating time, filtrating paper. was taken apart and the rest was thrown



    Figure 2: A visualization of our experiment


     The tables below show the amount of ml

     DCPIP needed for titration: