The effects of boiling and freezing on the Vitamin C concentration

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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:

    DCPIP Boiled Spinach DCPIP Normal Spinach

    Titration (1ml) - Test Titration (1ml) 0.4ml

    Titration 1 (10ml) 0.7ml Titration 1 (10ml) 4.05ml

    Titration 2 (10ml) 0.5ml Titration 2 (10ml) 4.90ml

    Titration 3 (10ml) 0.8ml Titration 3 (10ml) 4.55ml

    Titration 4 (10ml) 0.7ml Titration 4 (10ml) 3.95ml

    Type of spinach Average DCPIP DCPIP Frozen Spinach

    Test Titration (1ml) 0.2ml Normal 4.36ml Titration 1 (10ml) 0.5ml

    Frozen 0.825ml Titration 2 (10ml) 1.00ml

    Titration 3 (10ml) 1.10ml Boiled 0.675ml Titration 4 (10ml) 0.70ml





    Titration 1

    3Titration 2

    Titration 32

    Titration 4



    Normal spinachFrozen spinachBoiled spinach

    Figure 3: A graph of our results (DCPIP)

Mg Vitamin C in spinach

    Our DCPIP had a concentration of 9,14e-4

    or 0.000914 mol/liter and Vitamin C has a

    molecular mass of 176.13g

We can calculate the amount of mg

    Vitamin C using:

    (ml DCPIP) x 0.000914 x 176.13 = mg

    Vitamin C

    Vitamin C DCPIP Normal Spinach Boiled Spinach

    Test Titration) 0.064mg Titration -

    Titration 1 0.65mg Titration 1 0.11mg Titration 2 0.79mg Titration 2 0.08mg Titration 3 0.73mg Titration 3 0.13mg Titration 4 0.64mg Titration 4 0.11mg

    Type of spinach Vitamin C Average Vitamin C Frozen Spinach

    Test Titration 0.032mg Normal 0.70mg Titration 1 0.080mg

    Titration 2 0.16mg Frozen 0.13mg Titration 3 0.18mg

    Boiled 0.11mg Titration 4 0.11mg


    Mg Vitamin C





    Normal Spinach

    0,4Frozen Spinach

    Boiled Spinach0,3Mg Vitamin C




    State of Spinach

    Figure 4: A graph of our results (Average Vitamin C)

As you can see in the tables and the graphs

    our results seem to be pretty accurate. The

     measurements are pretty close together and no mistakes seem to have been made

     (otherwise one of the results would’ve been way off).

    As you can see the boiled and frozen

    spinach contain much less Vitamin C then the normal (fresh) spinach.

    The difference between boiled and frozen

     spinach seems to be rather small Since no weird measurements showed up,

     and because these results add to our hypothesis, we can conclude that these results are reliable.


    Evaluation Discussion and conclusion The experiment was fun to perform. The There definitely is a difference in the method used to determine the amount of Vitamin C concentration after boiling and Vitamin C was easy to use. The freezing. Boiling seems to have the biggest experiment was performed step by step and impact. There is a difference of 3,685 ml no grove mistakes were made. The DCPIP/0.59mg Vitamin C. After freezing experiment could however be improved. the difference is 3,535 ml DCPIP/0.57mg

    Vitamin C. For example, more portions of spinach

    could have been used. Also, the titration

    The answer to our research question ‘how could/should have been a little bit more

    big is the effect of boiling and freezing on precise. The tap on our burette was a bit

    the Vitamin C concentration of spinach?’ hard to operate, so we may have added too is that the effect is pretty big. If you look at much DCPIP. That way, our results the results you can see that there is a huge would’ve been a bit more reliable. We also difference in Vitamin C, approximately 6/7 didn’t have enough time to finish all our

    of the original Vitamin C has disappeared. planned tests. Originally we wanted to buy

    We can conclude that boiling and freezing some frozen spinach and see if Vitamin C

    has a big impact on the Vitamin C was added manually to counter the effect

    concentration of spinach and it’s healthier of freezing. Perhaps we could do this to eat spinach fresh. another time.


Cito Arnhem 1999 - Bepaling van het

    gehalte vitamine C in Spa Citroen

RIS-practica - Bepaling van het gehalte

    aan vitamine C


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