The effect of cooking time on the Vitamin C content.

“What is the effect of cooking time on the Vitamin C content in cabbage?”

            In the experiment, the investigated research question was, “What is the effect of cooking time on the Vitamin C content in cabbage” In this case, experiments were carried out to see how the time taken to boil cabbage affected the Vitamin C content of the cabbage.

            The amount of Vitamin C in a substance is acquired by using two main chemicals: orthophosphoric acid and the dye dichlorophenolindophenol (dcpip). In the experiment, orthophosphoric acid had been added to both the boiled cabbage and its water. And each was titrated using dcpip. This was repeated for different times. And the amounts needed for the titration were recorded. 

            The results obtained were used to plot a graph. This graph clearly showed the relation between the cooking time of the cabbage and the vitamin C content in it. It could be seen that as the cooking time increased, the amount of vitamin C in the cabbage decreased, while the amount in the water increased. It can be suggested that as the time passed, more of the vitamin C in the cabbage was either being destroyed or leached out into the water. This would also explain why the content in the water increased.

            However the graph may not be precisely accurate, as experimental data can never be perfect. The experiment was only carried out once. Thus, there are chances that there may have been some errors while carrying out the experiment.

            All in all, from the experiment carried out, it can be seen that in order to retain the vitamins in the food, the cooking time needs to be low. However, the food should not be served raw, as this too has its problems. Therefore, the cooking time should be kept minimum, i.e. just enough so that the food is cooked and not raw.

BACKGROUND INFORMATION:

            Vitamin C (ascorbic acid) is a substance that has been closely studied throughout history by many people. There have been many different experiments carried out to observe the effects of this substance. One such investigation was carried out in the department of Food Science and Microbiology, in the University of Milan by Serena Guarnieri, Patrizia Riso and Marisa Porrini.

Vitamin C seems to be the most effective antioxidant, as demonstrated in vitro studies (Szeto et al. 2002; Proteggente et al. 2002). Many in vivo studies have investigated the role of vitamin C in the protection against oxidative-induced DNA damage: single-dose trials showed significant antioxidant protection (Green et al. 1994; Panayiotidis & Collins, 1997. )

The ingestion of fruits abundant in vitamin C appears to increase the antioxidant defense of the organism. In spite of this, it is still not apparent whether vitamin C is the only substance responsible for this effect. The aim of this investigation was to study the effect of the ingestion of a single portion of blood orange juice (BOJ, 300 ml, providing 150 mg vitamin C) on mononuclear blood cell (MNBC) DNA damage, compared with a drink supplemented with the same amount of vitamin C (C-drink) or sugars (S-drink). Seven young healthy subjects were randomly selected in a repeated-measures design in which they received each drink on different occasions, 2 weeks apart. Blood samples were collected at baseline, every hour to 8 hour, and at 24 hour after the intake of each drink. The Vitamin C was analyzed at each time. Plasma vitamin C concentration increased similarly following BOJ or C-drink intake and was not affected by the S-drink. No effect of the C-drink and S-drink was observed. In conclusion, the intake of a single portion of BOJ provided an early protection of MNBC against oxidative DNA damage; however, the protective effect of BOJ was not explained by vitamin C alone, thus other phytochemicals could be involved.

RESEARCH QUESTION:

“What is the effect of cooking time on the Vitamin C content in cabbages?”

INTRODUCTION:

            Vitamin C, which is also known as ascorbic acid, is a water-soluble vitamin needed by the human body. It has a chemical structure of carbon, hydrogen and oxygen. Pure ascorbic acid (vitamin C) appears white in color. However, when it is impure, its color changes into a slightly yellowish color. Moreover, when it dissolves in water, it turns the water mildly acidic. Many animals can manufacture vitamin C in their bodies. Humans, however cannot, therefore we must obtain it from external sources. Vitamin C is a fundamental element of collagen, which is the structural substance for bones, skin and other tissues. [1] Also in the human body, sometimes during respiration oxygen is not fully reduced. Thus, it forms a superoxide ion. Generally, there is an enzyme that can solve this problem by changing the superoxide ion into H2O2 and O2. However, in the existence of Fe2+, the hydrogen peroxide may be converted into a highly reactive hydroxyl radical. This radical can start unwanted reactions in the cells when it removes a hydrogen atom from an organic compound to form H2O and another, possibly more reactive free radical. In order to stop this from happening, Vitamin C (ascorbic acid) is needed, as it can give a hydrogen atom to the free radical, which would then stop the reactions from occurring. This vitamin is normally found in fruits and vegetables such as in oranges, lemon, cabbages, Brussels and many more. Vitamin C is normally found in the watery part of the food, and hence it can be lost while cooking in water. [2] It was realized in the 1920’s that some cuts of meat and fish are also a source of Vitamin C for humans.[3]

            In addition, Vitamin C has the chemical formula C6H8Oand a molecular mass of 176.14 grams per mole (gmol-1[4]

Amounts of vitamin C in different foods vary. However, the amount of vitamin C in foods of plant origin depends on: the precise variety of the plant, the condition of the soil, the type of weather in which it grew, the length of time since it was picked, the storage condition and the method of preparation.[5] Cooking specifically destroys the level of vitamin C. My research question as you can see from the title is “What is the effect of cooking time on the Vitamin C content in cabbages?” and so will particularly be talking about the last mentioned point i.e. the cooking time of cabbage and how it affects the Vitamin C content. The cooking process I have picked is the boiling of cabbage. Cooking not only destroys the Vitamin C in fruits and vegetables, it also does so in the meat and fish, which are sources of vitamin C.

            Vitamin C is consumed for a variety of reasons: It is effective in treating Vitamin C deficiency, symptoms of the common cold, acne, gum disease and infections of the skin and bladder.

HYPOTHESIS:

As the cooking time of cabbage increases (i.e. the more the cabbage is boiled), the greater will be the amount of Vitamin C lost. Therefore, as you increase the cooking time of cabbage, the amount of vitamin C in the food will diminish.

APPARATUS AND MATERIALS:

METHOD:

Preparation of 2,6- dichlorophenolindophenol solution

            Dcpip is a dye which when placed in water turns blue, in acid it turns red, and when placed in ascorbic acid, it turns into a colourless compound. In order to prepare this solution, firstly, you need to dissolve 0.4 g of dcpip in deionised water. Then filter this and make the volume of the solution up to 1 dm. Since the dye easily spoils, it is best to keep it in a chilled and dark spot.

Standardization of the 2,6- dichlorophenolindophenol solution

            Seeing that it is very difficult to prepare the solution accurately, the most prudent thing would be to standardize it. Therefore, you would first have to transfer 25.0 cm of standard ascorbic acid solution to a conical flask and titrate it immediately with the dcpip. As the dye mixes in, its blue colour changes to give a colourless solution.  When the pink colouration due to the dcpip remains the same for around 10 seconds, it is considered to be the end point.

Testing the Vitamin C content in the water:

            Firstly, weigh out 10 g of finely chopped cabbage, which you would then place in 20 cm3 of boiling water for 5 minutes. While waiting, pour 50 cm3 of orthophosphoric acid in two different containers each. After the 5 minutes, filter out the cabbage but do not spill out the water. Place the water from the boiled cabbage into a beaker and measure the volume. Lets call this value ‘Vc’. Pour the 50 cm3 of orthophosphoric acid into the water. Next, transfer 10 cm3 of this solution to a conical flask. This should be done using a pipette. And then, titrate it with the dye (dcpip) Record this value.

Repeat the above experiment for different boiling times, i.e. 4, 3, 2 and 1 minute 

Testing Vitamin C content in the boiled cabbage:

            After filtering out the cabbage, you need to liquidize it. Pour the orthophosphoric acid from the other beaker into the liquidized cabbage and stir the mixture. Measure this mass and lets call this value ‘Mc’. Remove about 1/12th of this mixture, you can estimate this value; you do not have to be very precise. This fraction of the mixture should then be weighed. Lets call this value ‘mc’. Next, filter this mixture. The filtrate should be made up to about 5 cm3. Lastly, titrate the filtrate with the dcpip. And hence, record the value.

Repeat the above procedure for cabbage boiled for 4, 3, 2 and 1 minute each.

ANALYSIS:

(See Appendix for the raw data)

Amount of Vitamin C in the liquidized cabbage:

GENERAL FORMULA: 

Mass treated = 10 g

Mass sampled for titration = (mc/Mc) * 10 g

Volume of dye titre = V cm3

Dye factor = F mgcm-3

10 g of sample contains = V * F * (mc/Mc) mg of Vitamin C

50 g of sample contains = V * F * (mc/Mc) * 5 mg of Vitamin C

FOR 5 MINS:

Mass treated = 10 g

Mass treated for titration = (4.35 / 51.16) * 10 g

                                             = 0.85 g

Volume of dye titre = 4.9 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 4.9 * 400 * (4.35 / 51.16)

                                         = 166.65 mg of Vitamin C

50 g of sample contains = 4.9 * 400 * (4.35 / 51.16) * 5

                                         = 833.25 mg of Vitamin C

FOR 4 MINS:

Mass treated = 10 g

Mass treated for titration = (4.30 / 51.70) * 10 g

                                             = 0.83 g

Volume of dye titre = 5.4 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 5.4 * 400 * (4.30 / 51.70)

                                         = 179.65 mg of Vitamin C

50 g of sample contains = 5.4 * 400 * (4.30 / 51.70) * 5

                                         = 898.25 mg of Vitamin C

FOR 3 MINS:

Mass treated = 10 g

Mass treated for titration = (4.50 / 52.21) * 10 g

                                             = 0.86 g

Volume of dye titre = 5.6 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 5.6 * 400 * (4.50 / 52.21)

                                        = 193.1 mg of Vitamin C

50 g of sample contains = 5.6 * 400 * (4.50 / 52.21) * 5

                                           = 965.5 mg of Vitamin C

FOR 2 MINS:

Mass treated = 10 g

Mass treated for titration = (4.25 / 51.00) * 10 g

                                             = 0.83 g

Volume of dye titre = 6.0 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 6.0 * 400 * (4.25 / 51.00)

                                          = 200 mg of Vitamin C

50 g of sample contains = 6.0 * 400 * (4.25 / 51.00) * 5

                                          = 1000 mg of Vitamin C

FOR 1 MIN:

Mass treated = 10 g

Mass treated for titration = (4.00 / 47.30) * 10 g

                                             = 0.85 g

Volume of dye titre = 6.2 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 6.2 * 400 * (4.00 / 47.30)

                                          = 209.7 mg of Vitamin C

50 g of sample contains = 6.2 * 400 * (4.00 / 47.30) * 5

                                          = 1,048.5 mg of Vitamin C

Amount of vitamin C in water:

GENERAL FORMULA:

Original quantity of cabbage = 10 g

Proportion sampled for titration = 10 / (Vc + 250)

Volume of dye titre = V cm3

Dye factor = 400 mgcm-3

10 g of sample contains = V * F * ( (Vc + 250) / 25) mg of Vitamin C

50 g of sample contains = V * F * ( (Vc + 250) / 25) * 5 mg of Vitamin C

FOR 5 MINS:

Original quantity of cabbage = 10 g

Proportion sampled for titration = There was no water remaining in the beaker as all of it evaporated. Hence, titration could not be carried out.

FOR 4 MINS:

Original quantity of cabbage = 10 g 

Proportion sampled for titration = There was no water remaining in the beaker as all of it evaporated. Hence, titration could not be carried out.

FOR 3 MINS:

Original quantity of cabbage = 10 g 

Proportion sampled for cabbage = 10 / (5 + 250)

                                                         = 0.04

Volume of dye titre = 6.0 cm3

Dye factor = 400 mgcm-3

10g of sample contains = 6.0 * 400 * (10 / (5 + 250))

                                         =  94.1 mg of Vitamin C

50g of sample contains = 6.0 * 400 * (10 / (5 + 250)) * 5

                                         =  470.5 mg of Vitamin C

FOR 2 MINS:

Original quantity of cabbage = 10 g

Proportion sampled for titration = 10 / (9 + 250)

                                                         = 0.039

Volume of dye titre = 4.5 cm3

Dye factor = 400 mgcm-3

10g of sample contains = 4.5 * 400 * (10 / (9 + 250))

                                         = 69.5 mg of Vitamin C

50g of sample contains = 4.5 * 400 * (10 / (9 + 250)) * 5

                                         = 347.5 mg of Vitamin C

FOR 1 MINS:

Original quantity of cabbage = 10 g

Proportion sampled for titration = 10 / (10 + 250)

                                                         = 0.038

Volume of dye titre = 2.9 cm3

Dye factor = 400 mgcm-3

10 g of sample contains = 2.9 * 400 * (10 / (10 + 250))

                                         =  44.6 mg of Vitamin C

50 g of sample contains= 2.9 * 400 * (10 / (10 + 250)) * 5

                                         = 223 mg of Vitamin C

Summary of the results:

Time (mins)Amount of Vitamin C in liquidized cabbage (50 g)Amount of Vitamin C in the water (for 50 g)
11,048.5 mg 223.0 mg
21,000.0 mg347.5 mg
3965.5 mg470.5 mg
4898.3 mg   –
5833.3 mg   –

According to the graph above, as the time goes by, the amount of Vitamin C present in the cabbage decreases. In the graph below, it is evident that as the time goes, the amount of Vitamin C in the water increases. In addition, it is quite evident in the second graph that as the cooking time increases, the amount of Vitamin C lost in the water is more or less constant, and it is also quite high. This is because the gradient of the graph is quite steep.

CONCLUSION:

            The results clearly answered my research question, which stated, “What is the effect of cooking time on the Vitamin C content in cabbage?” According to the results received, it can clearly be seen that as the cooking time of the cabbage increases, the vitamin C content in the cabbage decreases. At the same time the amount of vitamin C in the water increases. For instance, you can see that at the time interval of a minute, the amount of vitamin C in the cabbage was approximately 1,000 mg and the amount that was present in the cooking water was approximately 223 mg. Moreover, when the time interval was 3 minutes, the amount of vitamin C in the cabbage was about 966 mg while in the cooking water it was approximately 471 mg. It can therefore be seen that as the cooking time increased the amount of vitamin C in the cabbage decreased and the amount in the cooking water increased. Thus, the hypothesis of this experiment was proven to be correct. Therefore unless you are planning to ingest that water or use it somewhere in your food, that amount of Vitamin C goes to waste.    

Many people do not realize the importance of Vitamin C in our daily diet. There are quite a few consequences that result due to low intake of Vitamin C. For instance, lack of vitamin C in the human body can cause a disease known as “scurvy.” The symptoms for this disease would include bleeding of the gums, fatigue and also the appearance of rashes. In the final stages, it is distinguished by intense fatigue, diarrhea and then kidney and pulmonary failure, which result in to death. Usually vitamin C is used to cure this condition before it reaches the final stages. Furthermore vitamin A and vitamin E need vitamin C to protect them from oxidation. Vitamin C acts as an antioxidant; it hunts for free radicals before they can do any damage to your DNA. 

SOLUTIONS ( HOW TO RETAIN THE VITAMINS ) :

How you prepare and cook your food will definitely affect the nutrient content in it. However, boiling isn’t the only cooking process that affects the Vitamin levels in the food. For instance, Vitamin C content in foods can also be decreased due to exposure to high levels of heat or cold, i.e. stir-frying, freezing, frying, microwaving foods will all lead to the content of Vitamin C to reduce.

            A study was published in the August 2009 issue of the “Journal of Zhejiang University Science,”(1) in which researchers investigated five techniques of cooking broccoli. The techniques investigated were: stir-frying, microwaving, steaming, boiling, and a combination of stir-frying and boiling. The investigation revealed that after five minutes of cooking broccoli florets, using each method, boiling destroyed the highest percentage of vitamin C. This shows us that even though boiling is not the only cooking process that reduces the Vitamin C content in foods, it is however, the technique that destroys the highest percentage of Vitamin C.

            There are quite a few ways in which you can retain vitamins in your food before, during, and after you boil them. Firstly, it is important that you do not immerse your vegetables in water before cooking them. This is because immersing uncooked foods in surplus of water before cooking leads to the water- soluble vitamins ( such as vitamin C ) seeping out into the water. Furthermore, the vegetables should be placed in a container and refrigerated up to the time when they need to be boiled. Refrigerating the vegetables ensures that they will last longer. However do not refrigerate at very low temperatures, as this too will diminish the Vitamin content in them. When you are ready to boil the vegetable, try to boil the whole vegetable if possible. Chopping up the vegetables will result in a larger surface area of the food being exposed to air and the extreme heat while boiling. Moreover, try to boil the vegetables in the least amount of water possible and for the shortest period of time. This will help reduce the vitamin content lost into the water. Once you have completed cooking the food, serve it immediately. When the food is exposed to air, it oxidizes and thus, vitamins are lost especially vitamin C. Therefore, the longer you leave the food out, more oxidation takes place and so you lose even more of the vitamins. In addition, as seen from the experiment: some of the vitamins that are leached out of the vegetables are present in the water used for cooking. Thus, try to use that water in your food, e.g. you could use that water in making curry or soup. 

BENEFITS OF COOKING:

            At this point, one may wonder why do we cook food if it is disadvantageous to us. There are some benefits that result from cooking: firstly, when you cook food, harmful micro organisms that are food- borne are destroyed. Additionally, the digestibility of many foods ( e.g. starch foods ) increases on cooking. Although this is not the most important benefit of cooking, most of us appear to love the fact that cooking leads to better appearance and palatability of the food.

ERRORS:

            Experimental data can never be perfect. There are two types of errors that can occur: random errors and systematic errors. Random errors are unpredictable i.e. you cannot control them. They can be in either direction – the results could be higher or lower – and the difference may be minute or large. Therefore, the only way to minimize random errors is to repeat the experiment several times. 

            In the above- mentioned experiment, the possible random errors could be: slight variations in the level of the eye while reading the meniscus. This would cause the value measured to be higher or lower than the actual value by around 0.1 cm3

            Systematic errors are a result of the way in which the experiment is carried out. Unlike random errors, these errors are in one direction i.e. the result would either be higher or lower. E.g. if a weighing scale is mis- calibrated then the result will always be either too low or too high depending where the mis- calibration is. 

            In the experiment there were quite a few systematic errors. For instance, the mass of the cabbage was probably not accurate. This is because while the experiment was going on the windows were open. And so the air currents caused the weighing balance to fluctuate. Therefore, the mass of the cabbage actually used in the experiment could have been greater or less than 10 g by around 0.01 g. Furthermore, during the experiment the water in the beaker completely evaporated for the time of 4 and 5 minutes. This therefore was a setback, as the amount of vitamin C lost into the water could not be calculated. When the experiment was being carried out the first time, I realized that the results did not make sense. On further investigation, it became clear that the dcpip had expired as it had been left out for quite some time. Therefore, the experiment had to be restarted, and this was an unexpected holdup

            In addition, due to time constraints, the experiment was only carried out once. Hence, there is a possibility that the values may not be very accurate due to random errors that are nearly impossible to avoid.

UNANSWERED QUESTIONS:

In the experiment, only the effect of boiling was seen on the Vitamin C content in cabbage. What was not examined was how other cooking methods would affect the Vitamin C content, e.g. frying, microwaving, and freezing cabbage. This was mainly due to the fact that the school did not have facilities where I could fry or microwave the cabbage and instantly test for the vitamin C content. However, I am set on continuing these experiments on my own in order to find the best method to cook my food in a healthy way. 

Is there a side effect of having too much vitamin C?

            Although it has not yet been proved, it is believed that consuming high doses of vitamin C especially in supplement form has caused mild, or in some cases severe headache. However, this only occurs to about 1% of the people who consume vitamin C supplements. Thus, it is not quite clear if too much vitamin C is the cause.

BIBLIOGRAPHY:

“Avoid soaking vegetables | Deccan Chronicle.” Deccan Chronicle – Latest India news | Breaking news | Hyderabad News | World news | Business | Politics. N.p., n.d. Web. 5 Nov. 2012. <http://www.deccanchronicle.com/channels/lifestyle/new-40s/avoid-soaking-vegetables-229>.

“Cooking and Preserving Nutrition.” webhealthcentre. N.p., n.d. Web. 5 Nov. 2012. <www.webhealthcentre.com/HealthyLiving/diet_nutrition_cooknut.aspx>. 

“How Does Boiling Affect Vitamin Content? | LIVESTRONG.COM.” LIVESTRONG.COM – Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools | LIVESTRONG.COM. N.p., n.d. Web. 5 Nov. 2012. <http://www.livestrong.com/article/474276-how-does-boiling-affect-vitamin-content/>.

Neuss, Geoffrey. Chemistry: course companion.. 2. ed. Oxford: Oxford University Press, 2012. Print.

“Orange juice vs vitamin C: effect on hydrogen peroxide-induced DNA damage in mononuclear blood cells.” www.aseanfood.info. N.p., n.d. Web. 5 Nov. 2012. <www.aseanfood.info/Articles/11021738.pdf>. 

“The hunt for vitamin C; t he ef fect of cooking processes on the vitamin C content of cabbage.” rsc.org. N.p., n.d. Web. 5 Nov. 2012. <www.rsc.org/learn-chemistry/content/filerepository/CMP/00/000/682/isms-4.pdf>.

“Vitamin C’s Side Effects | LIVESTRONG.COM.” LIVESTRONG.COM – Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools | LIVESTRONG.COM. N.p., n.d. Web. 5 Nov. 2012. <http://www.livestrong.com/article/403881-vitamin-cs-side-effects/>.

Your, your experience in the laboratory. Include all data in a table. Part of. “Determination of Vitamin C.” Truman State University ChemLab Guide. N.p., n.d. Web. 2 Dec. 2012. <http://chemlab.truman.edu/CHEM130Labs/VitaminC.asp>. 

APPENDIX 

RESULTS (raw data):

For water:

Boiling Time ( mins )Vc ( cm3 )Titration of water ( cm3 )
5 – –
4 – –
35 cm36.0
29 cm34.5
110cm32.9

For cabbage:

Boiling Time (mins)Mc ( g )mc ( g )Titration of liquefied cabbage ( cm3)
551.164.354.9
451.704.305.4
352.214.505.6
251.004.256.0
147.304.006.2

[1]“EatingWell.”eatingwell.com. Meredith Corporation., n.d. Web. 5 Nov. 2012. http://www.eatingwell.com/nutrition_health/nutrition_news_information/vitamin_c_why_do_we_need_it

[2]“EatingWell.”eatingwell.com. Meredith Corporation., n.d. Web. 5 Nov. 2012. http://www.eatingwell.com/nutrition_health/nutrition_news_information/vitamin_c_why_do_we_need_it

[3] “The Vitamin C molecule.”worldofmolecules.com.N.p., n.d. Web. 5 Nov. 2012. http://www.worldofmolecules.com/antioxidants/vitaminc.htm

[4] “The Vitamin C molecule.”worldofmolecules.com.N.p., n.d. Web. 5 Nov. 2012. http://www.worldofmolecules.com/antioxidants/vitaminc.htm

[5] “The Vitamin C molecule.”worldofmolecules.com.N.p., n.d. Web. 5 Nov. 2012. http://www.worldofmolecules.com/antioxidants/vitaminc.htm