Vitamin C in Different Fruit Juice
Activity 1. 21- Is high Vitamin C all it claims to be? Purpose: * To investigate the vitamin C content of fruit juice * To investigate which type of fruit juice provides the most vitamin C The quantity of vitamin C in food and drink can be determined using a simple colour test. Vitamin C decolourises the blue dye DCPIP (dichlorophenolindolphenol). Vitamin C is an antioxidant and reduces the DCPIP. DCPIP changes from blue to colourless (or slightly pink) as it becomes reduced. We will be testing a range of different fruit juices to see which contains the highest concentration of vitamin C Hypothesis: I predict that the orange might be the juice that provides the most vitamin C; this is because it is widely promoted as a ‘high vitamin C juice’. * Grapefruit juice might contain the second highest amount of vitamin C; also because of it promotion in the media. Vitamin C is a water-soluble compound that is essential for life. It is involved in many processes in the human body, including: the production of collagen in the connective tissue; the synthesis of dopamine, noradrenaline and adrenaline in the nervous system; and the synthesis of carnitine, which is important in the transfer of energy to the cell mitochondria.
A deficiency in vitamin C causes scurvy, a disease that affected sailors in the 16th – 18thCenturies. It was discovered that fresh fruit, e. g. limes and oranges, or sauerkraut (preserved cabbage) provided the sailors with protection from scurvy. Safety: * Running should be avoided in the laboratory to prevent accidents especially when handling liquids * Goggles should be warn at all times when carrying out the experiment * Care should be taken when handling glass wear * The supervisor should be informed about any spillages of liquid that may be hazardous to others in the laboratory. Controlled variables: Temperature; If a juice is higher in temperature than the other, it will cause the reaction to speed up which would make the experiment unfair. * Concentration of DCPIP; different concentrations would not benefit the experiment as we are only changing the type of juice. * Shake each flask using the same movements; more vigorous movements may add oxygen which would affect the DCPIP and turn it slightly blue again. * Same end point colour (colourless); attention and concentration should be given to see through until the very last drop so the volume is not increased. Independent variable: * Fruit juice Dependant Variable: Volume of juice required to decolourise the DCPIP. The experiment procedure: Equipment: * 1% DCPIP solution * Vitamin C solution * Range of fruit juices * Conical flasks * Beakers * Pipette accurate to 1cm3 to measure volumes accurately * Burette to measure volumes accurately * Safety goggles Method: 1. Pipette 1cm3 into a beaker 2. Fill the burette with the vitamin C solution 3. Add the vitamin solution in droplets 4. As soon as the DCPIP goes colourless, stop the burette and record the volume of vitamin C solution that was used. 5. Repeat this procedure with other juices 6. Repeat the experiment at least 2 times . Calculate the mean result for each juice Table of results: | Vitamin C| Orange| Grapefruit| Lemon| Blueberry| Pineapple| | 1| 2. 5| 3| -| 2| 13| | 0. 4| 2. 4| 1. 95| 1. 1| 3| 12. 75| | 0. 35| 0. 4| 1. 15| -| 0. 8| 8. 2| | 0. 1| 2. 1| 4. 7| 1. 7| 1. 5| 8. 2| | 0. 1| 1. 96| 4. 6| 2. 3| 1. 8| -| AVERAGE| 0. 39| 1. 96| 3. 08| 1. 9| 1. 8| 10. 5| Here the least volume of juice needed to decolourise DCPIP was the blueberry juice, followed by lemon then orange juice. From the experiment, blueberry juice provided the most vitamin C because less of it was needed in order to turn DCPIP colourless.
The pineapple juice was the juice that let out the highest volume from the burette in order to decolourise DCPIP; this is because it was the juice that provided the least amount of vitamin C. All of the juices had vitamin C in them as the highest volume was only 10. 5cm3. The results obtained from the experiment showed no relation to my hypothetical prediction. It may have been because of the experimental errors that had been overlooked whilst carrying out the experiment. The results from the experiment did not agree with the widely publicised fact that orange juice provides the most vitamin C.
A number of errors could have been made: the temperature may not have been the equivalent for all juices( the last juice to be measured may have been at a higher temperature than the rest causing the reaction with the DCPIP to hasten), the amount of shaking may of effected the results as too much shaking could have added oxygen which would have restored the DCPIP to blue, the end point may have been difficult to judge because of it close proximity, some juice may have been lost whilst it was being transferred from the beaker , there might have been an error in how accurate the juices were measured or recorded.
In the future more attention could be given and the experiment could be done more slowly; time may have been an issue when carrying out the experiment. The results obtained were pulled together from different groups in the class who may have all treated their readings and measurements differently, therefore it would be much reliable if I repeated the experiment and obtained at least three readings for each juice on my own. Moreover, the juices bought could all be from the same brand, this is because some manufacturers put more sweeteners or fresh juice than others.