I predict that the longer the length of cooking time is, the lower the vitamin C content will be.
To keep it a fair test I am only going to have one variable which will be the length of cooking time. I intend to keep everything else constant. So I shall use the same amount of peas, same temperature and volume of water and allow an equal crushing time of each sample.
* Bunsen burner, tripod, gauze, heat proof mat
* 1 Litre beaker, 600ml beaker, 10cm3 measuring cylinder
* 50ml beaker, 2cm3 syringe, Pasteur pipette
* Stopwatch, 60 frozen peas (5 for each boiling tube), sand, mortar pestal, ice
* 14 boiling tubes, 2 boiling tube holders
* DCPIP (100cm3) 0.01% concentration, 20 ml of Vitamin C standard
* Safety goggles, lab coat
* Gather all equipment
* Set up water bath
* Take a 1L beaker – fill with 500ml of cold water
* Leave to boil – temp 100oC
* Take 10 uncooked peas and place 5 into tube labelled 0 mins
* Place the remains 50 peas into the boiling water
* From the moment they go in start timing.
* At each time interval (2,4,6,8,10mins) take 10 peas and place them into the 2 corresponding boiling tubes (ie. at 2 mins place 5 peas into both tubes marked 2 mins)
* Place complete tubes in ice beaker.
* Once all cooked and cooling take a tube sample, 10cm3 of water and a pinch of sand – place in mortar pestal. Crush for 1 min.
* Next take 2cm3 syringe and fill with DCPIP, put DCPIP in corresponding boiling tube
* Then take the crushed solution, add drop by drop in DCPIP using Pasteur pipette
* Count amount of drops taken to clear the blue coloured DCPIP
* Record results
* Do for all 6 intervals (0,2,4,6,8,10 mins)
* Repeat the experiment
To reinforce what I have said in my prediction I can say that I know that cooking reduces the amount of vitamin C levels in food.
Avoid skin or eye contact with DCPIP Wear safety goggles
Wear lab coats When not in use turn Bunsen to an orange flame
Reasons for choice
I am going to use frozen peas as opposed to fresh, raw peas as there is a higher level of vitamin C present. I know this because immediately after harvest 50% of vitamin C may be lost.
I am going to boil the peas as I know that heat disrupts the cell membrane which in turn causes a leakage of Vitamin C. Vitamin C is also water soluble so I know that it can be easily extracted.
I am using six intervals to obtain an accurate set of results which will allow me to see a significant drop in the vitamin C thus proving that the levels of vitamin C do decrease. I shall use a two minute regime as opposed to a one minute regime to ensure I achieve accurate results. I feel that using a one minute time regime would be less accurate as the timings are too close together.
I am going to place the cooked samples in a beaker of ice as I know that enzyme reactions can not occur in very hot or cold surroundings (below 5oC or above 63oC.) I want to ensure that it is a fair test which is why after being cooked I intend to try and stop further reactions taking place.
I am intending to use sand in the preparation of the vitamin C extract as it is an abrasive which will allow me to form the liquid I intend to use. I am using the 10cm3 quantity of water in preparation of the vitamin C extract as I feel that it will be necessary in ensuring I have an adequate amount of solution. 2peas = 1cm3 water.
I am going to use 5 peas for each sample, as peas are all different sizes and by using 5 peas I should have an even sized range for me to test thus making it a fair test.
Secondary source of data
I have used the internet as my secondary source of information. The information I collected explained to me about the levels of vitamin C present in frozen/raw food. It also gave details of how cooking affected these levels.
Testing a standard
I must ensure that I test a standard before I conduct my experiment. This will allow me to determine the Vitamin C content of a known substance. I am going to do this as in a previous experiment we did this and provided a base on which to work on. From here I shall then be able to work out my calculations from the set of results I am going to obtain. I shall use the following equation to do so:
Number of drops of 0.01% VIT C
Vitamin C content = ——————————– * 10 = ….mg/100cm3
Number of drops per sample
I am going to cook an amount of peas using the above method to determine whether the levels of vitamin C decrease when left at different intervals. I shall then test my samples using DCPIP and the calculation above to indicate the vitamin C content of each timed sample.