Cooked or Uncooked?

Breanne Chausse and Claudia Dunn


How does cooking citrus juices effect the amount of vitamin C?


The purpose of this experiment is to determine if more vitamin C can be found in cooked or uncooked citrus fruits.


Vitamin C, also known as ascorbic acid, is a water-soluble nutrient that can be found in some foods. This vitamin is crucial to the way the human body works, it improves the absorption of iron which can help the immune system work properly to protect the body from diseases. In the body it acts to protect you from free radicals such as, cigarette smoke, air pollution, and some ultraviolet light from the sun. Vitamin C is also used for the growth and repair of all tissues in parts of your body such as, tendons, skin, ligaments, and blood vessels. The body is not able to make vitamin C on its own,it also unfortunately does not store vitamin C on its own. It is therefore important to include plenty of vitamin C-containing foods in your daily diet. For many years, vitamin C has been a very common remedy for the common cold, researchers have found that for most people, vitamin C supplements foods do not reduce the risk of getting the common cold. However there are some downsides, people have found that taking vitamin C during the cold does not affect it in any sort of way.

Usually when people think of vitamin C they automatically go to the assumption that oranges is the only food the provides vitamin c, that would be false. Fruits that include high rates of vitamin C are, cantaloupe, papaya, berries, mango, kiwi fruit and, citrus fruits. Vegetables that includes high rates of vitamin C are, tomatoes and tomato juice, brussels sprouts, spinach, cauliflower, green and red peppers, cabbage, turnip greens, sweet and white potatoes, and winter squash. Some cereals and other foods and beverages are also included under the Vitamin C category. Although consuming vitamin C is very beneficial to how your body works, consuming too much has some serious side effects although they are very rare. Consuming too much can lead to Anemia, bleeding gums, decreased ability to fight infection, decreased wound-healing rate, dry and splitting hair, easy bruising, Gingivitis(inflammation of the gums), or nose bleeds. This is due to the fact that the body can not store any of the vitamin C, amounts greater than 2,000 mg/day are not recommended. The amount of vitamin C you should be having can differ according to your age or gender. Smokers need an additional amount each day.

Vitamin C storage is very rare in the United States. People who get little or no vitamin C (below about 10 mg per day) for many weeks can get scurvy. Scurvy causes fatigue, inflammation of the gums, small purple or red speckles on the skin, corkscrew hairs, and poor wound healing. Additional signs of scurvy include depression as well as swollen, bleeding gums and loosening or loss of teeth. People with scurvy can also develop amnesia. Scurvy is fatal if it is not treated.

How vitamin-rich food is also important when trying to fill your daily amounts. The shorter the time it takes for the food to get from the farm to your plate, the better. When foods are freshly picked and eaten right away, the more nutrients and vitamins you will receive for it. If they food you're about to eat isn’t farm fresh, steam or microwave it so you can preserve all the possible nutrients. Boiling destroys vitamin and nutrient levels in foods because boiling keeps the food at a very high temperature for an extended period of time.

Without the essential vitamins and nutrients to the body, including vitamin C, our bodies cannot create collagen. Collagen is a protein in our bodies that give structural support and provide strength to connective tissues such as ligaments, tendons, bones, skin, and blood vessels. Collagens are found all over the body, in many different areas. They may all be different, but they share the fact that they are made of cells and are secreted into the intercellular substance, better known as the material around a cell.

Iodine is a halogen. Halogens are part of 7th group on the periodic table, which means the are salt producers. At ordinary temperatures, the element is solid. Iodine has an irritating order and has a bluish black color. When iodine is a gas, it has a purple color. Iodine has 53 protons and 73 neutrons, in its most common form. This element sublimes when heated. This means instead of turning into a liquid from a solid, it turns directly from a solid into a vapor when heated.

When combined with the amino acid tyrosine, thyroxine is produced. The thyroid gland in our bodies use iodine to make a hormone known as thyroxine. Thyroxine manages the rate of both physical and mental development in our bodies. A deficiency in this element can hinder growth and produce a larger form of thyroxine, called goiter. Goiter are also caused by dietary problems. Goiter isn't common in right now, because of iodized salt. Before salt was iodized, certain areas of the planet were more likely to have goiters commonly. These areas were particular regions of Africa, remote villages in Peru and South America, and the Great Lakes regions of the interior of the U.S.

If pure iodine is consumed, it is poisonous. In photographic film, the key light-sensitive substance is iodine. Iodine and compounds containing iodine can also be used as a disinfectant for purifying water. Iodophors are complex compounds that has almost entirely replaced tinctures of iodine. Both are used as a first-aid antiseptic, even though tinctures of iodine can irritate wounds. Iodine is also known to oxidize, or gain electrons from other substances, like other halogens, to create new compounds. Iodine is known as an indicator because it changes color in the presence of certain substances, especially starch. The iodine molecule changes color when two substances meet in a chemical reaction.


If the amount of vitamin c is tested for cooked and uncooked samples of citrus juice, then the uncooked juice will have more vitamin C because it has not been exposed to heat extremes.


Citrus fruits (Lemons, limes, grapefruits, oranges)

· Water

· Iodine

· Cornstarch

· Pot

· Eyedropper

· Stove

· Clear glasses


Preparing the Iodine Indicator

  1. Mix water and 1 tbsp of cornstarch together, making a paste

  2. For a total of 5 minutes, boil the paste and an additional 250 mL of water

  3. Add 10 drops of the boiled solution to 75 mL of water, using the eyedropper or pipette

  4. Continually add drops of iodine to the mixture until it turns dark-purple in color

Testing for Vitamin C

  1. Squeeze juice out of the fruit equally into two separate containers. Label one “heated” and one “original”

  2. Transfer the “heated” juice from container to the pot. Heat the “heated” sample on the stove top until it comes to a boil. When it comes to a boil, remove from the stove

  3. Using the eyedropper, add 5 mL of iodine indicator solution to “heated” container. Add 10 drops of cooked juice to the container using a clean eyedropper to prevent contamination.

  4. Repeat step 3 for the juice sample labeled “original”

  5. Once both substances have combined, observe the two samples to see which one has a darker color, because the darker the color, the less vitamin C the sample contains

  6. Record data and repeat with other juice samples


Dependent Variable: amount of vitamin C

Independent Variable: juice/fruit type

Control: original sample that has not been heated

Experimental Group: original samples that has not been heated

Constants: amount of each sample, amount of iodine indicator


  • When making the Iodine Indicator (as shown in procedure) we noticed that the boiling substance turned into a gel form.

  • After several drops of the iodine indicator to the substance (citrus fruit that was heated), we noticed that typically the substance turned a dark purplish color.

  • The citrus juices labeled “cooked” were a darker and more dense color after being cooked and adding the iodine indicator.

  • The raw substance turned out to be a clear/purple color indicating that there is more vitamin C in the uncooked juice.

  • No matter the fruit the cooked color was the same of the juice and the same regarding the raw substance.

  • We ended up needing more amounts of fruits than others. For example we needed more limes than grape fruits since the grapefruit has a much larger capacity.

Data Tables

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Data Graphs


Statistical Analysis/Calculations



In the experiment, it was observed that uncooked or raw juice has a greater vitamin C content versus juice that has been heated and have been exposed to heat extremes. In all of the data that was collected, cooked juice has less vitamin C when compared to uncooked juice. For example, when orange juice was heated, the vitamin C content was significantly lower than the original sample. After the lime juice was boiled and compared to the original juice, the original juice was slightly lighter than the heated one. In the lemon test, both samples were considerable dark, but the uncooked sample was still lighter than the heated sample. When the heated grapefruit juice was compared to the raw sample, the cooked sample was much darker than the raw sample. As seen in all of the data, juice samples that have been cooked have far less vitamin C. Exposing citrus juice samples to heat extremes destroys it’s nutritional value. Vitamin C is water-soluble, making it very sensitive to heat. When sensitive vitamins, such as vitamin C, are exposed to extreme temperatures it destroys the possible vitamin contents.

Sources of Error

While performing the experiment there are some possible errors that could have taken place, although they would not change the procedure or results drastically. One error could be the amount of vitamin C originally found in the fruit. Another could be the drops of iodine added to both the heated and raw substance


After performing our experiment, we found that with heating the citrus fruit juice it loses its amount of Vitamin C due to heat extremes. Therefore, more vitamin C can be found in raw substances.


A continuation of this experiment could test other fruits and vegetables that have a high nutritional value, and test to see how the nutritional benefits are affected by high temperatures. The experimental design could be improved by getting a numerical value for the data collection. Having numerical data would make it easier to plot out which food has the most vitamin C or nutrients.


The experiment is beneficial to real life because its important to get the most nutrition out of the foods we consume. With poor eating choices comes an unhealthy lifestyle. Natural foods offer the most nutritional benefit when they are being consumed raw or minimally cooked. Along with vitamin C, vitamin B is also very sensitive to heat because it is a water-soluble vitamin. When natural foods go under extremes in heat, it destroys the nutritional values and makes it less beneficial to the body.