Vitamin C (ascorbic acid) is an antioxidant that is essential for human nutrition. Vitamin C deficiency can lead to a disease called scurvy which is characterized by abnormalities in the bones and teeth. Many fruits and vegetables contain Vitamin C but processing or storage destroys the vitamin.
A blue substance called 2 , 6-dichorophenolindophenol or DCPIP acts as an indicator. It changes from blue to red with acids but loses its colour in the presence of certain chemicals. One of which is ascorbic acid. DCPIP solution can be used to test for the presence of vitamin C in foods
P1 Task 3
I believe that the colour of the juices will change as the DCPIP (indicator) is added.
P3 Task 4
To determine the amount of Vitamin C in different fruit juices Risk Assessment:
Take care with fragile glassware such as burettes
Use a lab coat to prevent substances to transfer onto skin and clothing Use gloves to prevent substances coming contact with the skin Use goggles to prevent substances getting into the eyes
3 Different Fruit Juices – Tomato, Pineapple, Orange
a. Pipette 5 cm3 of DCPIP solution into a beaker.
b. Fill burette with any of the fruit juice
c. Record the amount of fruit juice added.
d. Turn on the burette’s knob while swirling the beaker until the colour changes.
e. Repeat the procedure and calculate an average result.
f. Repeat with the fruit juices to be tested. If more than 5 cm3 of DCPIP are completely decolourised, dilute the fruit juice and repeat the test. If the fruit juice has a strong colour that will interfere with determining the end point, dilute the juice before testing.
g. Calculate the amount of vitamin C in the standard solution mg cm-3. Calculate how much vitamin C there is in each of the fruit juices in mg cm-3. (mg/cm3 = concentration of the vitamin C)
References for Testing fruit juices for Vitamin C
Society of Biology: http://www.nuffieldfoundation.org/practical-biology/measuring-vitamin-c-content-foods-and-fruit-juices “Does the amount of Vitamin C change when a fruit gets older” http://www.livestrong.com/article/517371-does-the-amount-of-vitamin-c-change-when-a-fruit-gets-older/ Testing Foods for Vitamin C: http://www.foodafactoflife.org.uk/attachments/ff2caf4a-75e5-4aa129132873.pdf How to test for vitamin C with DCPIP: http://www.youtube.com/watch?v=GTqHHgtc4cw M1 Task 2
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