Why does the colour leak out of cooked beetroot
Why does the colour leak out of cooked beetroot?
Purpose of the Experiment
* To investigate the effect of temperature on membrane structure.
Hypothesis
I predict that as the temperature of the water in which the beet root is placed in is increased, the amount of pigment leaked will increase i.e. the solution will become darker in colour.
My prediction is based on the concept that cell membranes will breakdown if the temperature rises. Membranes are made of a bilayer of phospholipids and protein molecules. The key aspect to notice here is that the cell membrane is made of proteins, which are made up of chains of amino acids. The linking of amino acids is strong in a protein, however the three dimensional shape of the protein is determined via hydrogen bonds which are relatively weak and can be broken by heat and chemicals. Once the hydrogen bonds are broken the protein can no longer function correctly, as is the case in the cell membrane. I believe as the heat rises the proteins that make up the permeable cell membrane will break down and the betalain pigment in the beetroot cells will leak out. The stronger the heat, the more the proteins will denature and more betalain will leak out.
Method and Materials
To carry out this experiment we used:
• Raw beetroot
• Size 4 cork borer
• White tile
• Knife
• Ruler
• Water baths at 0, 10, 20, 30, 40, 50, 60, 70 ?C
• Plastic beaker, about 250 cm3
• 2 boiling tube racks
• Crushed ice
• 8 boiling tubes
• Thermometer (one per water bath)
• Colorimeter
• Cuvettes
• Stopclock
• Distilled water
• Pipette for measuring 2 cm3
• Small measuring cylinders
Instructions
Cut sections from a single beetroot using a size 4 cork borer. ...
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• Size 4 cork borer
• White tile
• Knife
• Ruler
• Water baths at 0, 10, 20, 30, 40, 50, 60, 70 ?C
• Plastic beaker, about 250 cm3
• 2 boiling tube racks
• Crushed ice
• 8 boiling tubes
• Thermometer (one per water bath)
• Colorimeter
• Cuvettes
• Stopclock
• Distilled water
• Pipette for measuring 2 cm3
• Small measuring cylinders
Instructions
Cut sections from a single beetroot using a size 4 cork borer. Cut eight, 1 cm length slices from these sections. Be careful not to spill beetroot juice on your skin or clothing as it will stain very badly.
2 Place the slices in a beaker of distilled water. Leave overnight to wash away excess dye.
3 Next day, place eight labelled boiling tubes each containing 5 cm3 distilled water into water baths at 0 ?C, 10 ?C, 20 ?C, 30 ?C, 40 ?C, 50 ?C, 60 ?C and 70 ?C. Leave for 5 minutes until the water reaches the required temperature. Place one of the beetroot sections into each of the boiling tubes. Leave for 30 minutes in the water baths.
4 Remove beetroot sections; shake the water/solution to disperse the dye.
5 Switch on the colorimeter and set it to read % absorbance.
6 Set the filter dial to the blue/green filter.
7 Using a pipette accurately, measure 2 cm3 distilled water into a cuvette. Place the cuvette into the colorimeter, making sure that the light is shining through the smooth sides.
8 Adjust the colorimeter to read 0 absorbance for clear water. Do not alter the setting again during the experiment.
9 Place 2 cm3 of the dye solution into a colorimeter cuvette and take a reading for absorbency. Repeat the readings for all the temperatures.
Results
Temp ?C
0
0
20
30
40
50
60
70
Absorbance (Series 1)
0
0.0
0.0
0.08
0.34
0.48
0.61
0.88
Absorbance
(Series 2)
0
0.0
0.0
0.05
0.31
0.43
0.63
0.81
Conclusion
By analysing the results I obtained it is possible to conclude that as the temperature increases the absorbance rating increases. This correlation shows that the temperature has an affect on the amount of betalain leaked from the pieces of beet root. My Conclusion concurs with my prediction, that as the temperature of the water in which the beet root is placed in is increased, the amount of pigment leaked will increase i.e. the solution will become darker in colour.
My results also show that during 0 ?C, 10 ?C, 20 ?C no beet root leaked out. This may be due to the fact that proteins do not denature at temperatures below 30 ?C, and the cell membrane does not breakdown. However after 30?C you can see a steady rise in absorbance levels. A slight absorbance reading level at 30?C shows that the very little proteins may have denatured whereas after 30?C the absorbance readings increase rapidly. The proteins in the cell membrane are made up of amino acids. The linking of amino acids is strong in a protein, however the three dimensional shape of the protein is determined via hydrogen bonds which are relatively weak and can be broken by heat and chemicals. Once the hydrogen bonds are broken the protein can no longer function correctly, as is the case in the cell membrane.
Evaluation
Note: A colorimeter is generally any tool that characterizes colour samples to provide an objective measure of colour characteristics. In chemistry, the colorimeter is an apparatus that allows the absorbance of a solution at a particular frequency (colour) of visual light to be determined. Colorimeters hence make it possible to ascertain the concentration of a known solute, since it is proportional to the absorbance.
The experiment was carried out twice to insure reliability and accuracy, however to increase both reliability and accuracy the experiment should be carried out a few more times.
Systematic errors that might have occurred are that the colorimeter may have been calibrated incorrectly; however this would indicate that m results are reliable yet not accurate.
The cleanliness of the cuvettes, whilst handling, may have also affected the absorbance level. As greasy hand marks may have absorbed more light then intended. This error may have occurred with all the cuvettes, again making the results reliable but not accurate.
Do insure accuracy better quality incubators may have been used for heating the water and keeping the independent variable, temperature, constant (for each set of temperature).
If the temperature fluctuated then this could have a direct impact on the results, as more or less cytoplasm may have leaked out (depending on temperature).
Another possible factor that may have affected the absorbance rating may have included the washing of the beetroot and the size of the pieces. If the beetroot has not been cleaned properly some betalain may be present from when cutting the pieces. If the sizes of the beetroot are different this could imply that more are less betalain is leaked. A larger piece would mean that there is more chance of more cytoplasm being leaked and vice versa with a smaller piece.
By considering the biology behind this experiment I think that the set of results are reliable and accurate.
Abdul Samad Farhat Biology AS
