Effect of Temperature on Vitamin C Content: Lab Report

Introduction

A daily intake of Vitamin C is essential for humans. Without it, the disease scurvy develops as sailors, explorers and people during the long winters in the Northern hemisphere found before the time of Captain Cook. The British Navy started giving sailors lime juice to prevent scurvy on long voyages in 1795. Vitamin C is found in high levels in foods such as oranges, limes, lemons, blackcurrants, parsley and capsicums. Vitamin C is water soluble and is therefore not stored or synthesized in the body, thus a daily supply is required.

It breaks down, and is no longer effective due to factors such as extreme temperatures or storage for more than a few days.

Aim:

To investigate the effect of temperature of juice on the content of Vitamin C.

Variables:

• Independent Variable: Temperature of orange juice (25°C, 50°C, 100°C)
• Dependent Variable: Content of Vitamin C (measured by the number of iodine drops)
• Controlled Variables:
  • Amount of orange juice (2mL, measured using a 25mL pipette)
  • Amount of starch solution (2mL, measured using a 25mL pipette)
  • Amount of hydrochloric acid 1M (2 drops from a dropper bottle)
  • Amount of distilled water (4mL, measured using a 25mL pipette)
  • Molar concentration of hydrochloric acid (HCl) – 1M, controlled using the same dropper bottle of HCl each time

Hypothesis:

As the temperature of the juice increases the content of Vitamin C will decrease.

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Materials and Methods

Materials:

1. Nudie orange juice
2. Iodine
3. Starch solution
4. Dropper bottle hydrochloric acid 1M
5. Distilled water
6. 3 conical flasks
7. Test tube rack
8. Bunsen burner
9. 25mL pipette
10. 250mL beaker
11. Heat proof mat
12. Safety Glasses
13. Thermometer
14. Gloves
15. Safety coat

Methodology:

1. Place 10mL of Nudie orange juice in a 250mL beaker.
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2. Using a Bunsen burner, heat the juice to 25°C.
3. Measure temperature by placing a thermometer in the juice.
4. Once juice is 25°C, using a 25mL pipette, add 2mL of the juice into a clean conical flask.
5. Using a 25mL pipette, add 4 mL of distilled water and 2mL of starch solution.
6. Add 2 drops of hydrochloric acid 1M (HCL).
7. Using a dropper bottle of iodine, add iodine drops counting the number of drops added and mixing the solution after each drop.
8. Once the solution starts to turn purple, record the number of iodine drops added for purple to appear.
9. Clean conical flasks using water.
10. Repeat steps 1-9 with 50°C juice and 100°C juice. Complete 3 trials for each.

Risk Assessment:

Results

Table 1: Effect of temperature of juice on the content of Vitamin C

Discussion

Vitamin C also known as ascorbic acid is an essential water-soluble nutrient for humans and some animal species. Vitamin C acts as an antioxidant serving to prevent cellular damage which is the common pathway for cancer, aging, and a variety of diseases. Vitamin C is also required to make collagen, a protein that aids the healing of wounds. The body also needs vitamin C as it improves the absorption of iron and supports the immune system. Vitamin C can be found predominantly in citrus fruits and green vegetables. The Recommended Daily Intake (RDA) is 60 mg per day. Vitamin C deficiency may cause Scurvy. Taking too much vitamin C can cause diarrhea, nausea and stomach cramps. Vitamin C is the most unstable vitamin which can be easily denatured. At high temperature, in the presence of sun light and oxygen present in air, vitamin C reacts and it is oxidized. Excessive amounts of heat can destroy vitamin C completely. At 70°C vitamin C is denatured so it should be preserved below 70°C to avoid heat damage. This experiment should show a result of decreased vitamin C content as the temperature is increased. It can be seen from the results table and graph of this experiment that the lower the temperature the more vitamin C is present in the orange juice. Each trial was fairly precise and the average showed a near consistent decrease in vitamin C content as the temperature increased. The average drops at 25°C were 14 and the average at 100°C was 4 showing a decrease in 10 drops.

The results supported the hypothesis as it was clearly seen that as the temperature of the juice increases the content of Vitamin C will decrease. The procedural method was solid and straightforward. There were, however a couple possible sources of error. Using droppers to measure the hydrochloric acid and add the iodine is not very accurate and may produce different quantities which could affect the results. This random error maybe reduced by getting a more accurate measuring device. The major problem however was the interpretation of the colour purple once adding the iodine drops. This is a random error as it affects each result differently depending on the interpretation. To reduce this error, a colour chart should be used to compare with the solution to give a more accurate result on the interpretation of purple. Oxygen and sunlight also denatures vitamin C. The longer the juice was left in the open the more oxygen and sunlight that could decrease the content of vitamin C. The method needs to be changed so that it states to put the lid back on the orange juice or a specific time added so each trial the juice is exposed to air for the same amount of time to get more precise results.

Conclusion

Vitamin C is the most unstable vitamin which can easily be denatured. The investigation was successful with some random errors however the results still supported the hypothesis. Only minor changes are necessary to the experiment but overall the results coincided with the research of the effect of temperature on vitamin C content. To keep high presence of vitamin C while cooking it is recommended that the vegetables are cooked in low heat and small amounts of water for short periods to minimize the loss of vitamin C.

Bibliography

• Admin. (2013, February 14). At What Temperature Does Vitamin C Denature? Retrieved April 15, 2014, from Vitaminable: http://www.vitaminable.com/at-what-temperature-does-vitamin-c-denature.html
• Ehrlich, S. D. (2011, July 7). Vitamin C (Ascorbic acid). Retrieved April 15, 2014, from University of Maryland Medical Center: http://umm.edu/health/medical/altmed/supplement/vitamin-c-ascorbic-acid
• Office of Dietary Supplements. (2011, June 24). Vitamin C. Retrieved April 15, 2014, from Office of Dietary Supplements - National Institutes of Health: http://ods.od.nih.gov/factsheets/VitaminC-QuickFacts/