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How does heating foods affect the amounts of Vitamin C they contain

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Laura Wetherill 10FJWa 18th May 2001 How does heating foods affect the amounts of Vitamin C they contain? Aim The aim of the experiment is to investigate how much Vitamin C / Ascorbic Acid is destroyed when Orange juice is heated at 80?C for different lengths of time. Introduction Certain foods contain high concentrations of Vitamin C. When these foods are heated their ascorbic acid content decreases, this is a non-reversible reaction. During the sterilisation process foods are heated and Vitamin C is destroyed. In order to maintain the initial concentration, Ascorbic Acid is added. DCPIP (dichlorophenol-indophenol solution) is a dark blue indicator that turns colourless when a certain amount of Ascorbic Acid is detected. The experiment is to determine the concentration of ascorbic acid present in five different solutions of orange juice, each of which has been pre-treated in a different manor as specified in table 1: Table 1 Solution number Pre treatment conditions 1 Heated at 80?C for 1 minute 2 Heated at 80?C for 2 minutes 3 Heated at 80?C for 3 minutes 4 Heated at 80?C for 4 minutes 5 Heated at 80?C for 5 minutes Fair Testing * The temperature of a substance affects the rate at which it reacts with another. ...read more.


* Pour 2mls of DCPIP into five of the test tubes and place them in a second test-tube rack. * Place the five test tubes containing the source of Vitamin C into the water bath (set at 80?) and start the stopwatch. * Remove one of the test tubes after 1 minute, another after 2, 3, 4 and 5. * Label the solutions 1 - 5 (1 being one minute and 5 being five minutes.) * Leave the orange solutions to cool down to room temperature. * Fill the glass pipette up with solution one by using the pipette filler. * Slowly add the orange juice to one of the test tubes containing DCPIP until it goes colourless. * Record the volume of orange juice added in millilitres. * Repeat this method 2 more times. Using the same equipment for multiple results. Results Table 2 Solution Number Heating time @ 80?C (Minutes) Results 1: Amount of Orange juice added to DCPIP. (Millilitres) Results 2: Amount of Orange juice added to DCPIP. (Millilitres) Results 3: Amount of Orange juice added to DCPIP. ...read more.


Concentrations of Ascorbic Acid The results that I gained showed me how much Orange juice after being heated for 1-5 minutes was needed to turn 2mls of DCPIP colourless. However they didn't tell me the concentration of the Ascorbic Acid content left after the heating process. If we refer to Graph 3 the concentration content in each solution can be gained. Graph 3 To gain the concentration of a solution after being heated, multiply the amount of Orange juice added to the DCPIP to turn it colour less by 100. This has to be don e because the line of the graph does not continue as far down as e.g. 0.38. Next read off 38 on the y-axis and follow along the x until you reach the line. Continue downwards along the y-axis and read off the value of the x. Divide the value of x by 100 and this will give you the concentration of the Ascorbic Acid content in 1/1000M. Divide the result by 1000 and this will give the concentration in Molar units. E.g. Solution Number Results Set Amount of Orange used. Concentration 1 1 0.38 mls 0.000001 M ...read more.

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