WHY DOES THE COLOUR LEAK OUT OF COOKED BEETROOT?
Temperature has an effect on the leaking of the colour from beetroot. This means that as the temperature is altered there will be a change in the rate of colour leakage.
Beetroot is a very familiar vegetable and is commonly known as beet. It is famous in most recipe books that advice that its outer skin is not to be removed to avoid getting red dye in the cooking water. If we look at the internal structure of beetroot, it will be observed that it consists of cells which are surrounded by a cell membrane. This cell membrane structure separates the contents of the cell from outside. The membrane has tiny holes in it which allows small molecules to pass through but not larger ones. This is known as semi-permeability. Beetroot contains red pigments called betalains in the cell vacuole and normally do not pass through the membrane. However when cooked, the dye leaks out and so I am investigating the effect of different temperatures on the amount of dye and the extent of damage on the beetroot membrane structure which causes the holes to allow larger molecules through. For molecules to move as a whole, they require a certain amount of energy. This energy may be supplied in the form of heat. Heat energy can be measured as temperature which is the degree of hotness or coldness of a body. It can be predicted that as temperature increases, the reading of the colorimeter will increase since betalain molecules will acquire enough energy to move through the membrane by active transport. There is also the possibility of temperature affecting pore size. As temperature increases, pore size increases. The colorimeter reading will implicate how much of the betalain has moved out through the membrane since that amount is directly proportional to colour given out.
Cut Sections from a single beetroot using a size 4 cork borer. Cut eight, 1cm length slices from these sections. Be careful not to spill beetroot juice on skin or clothing as it will stain very badly. Place the slices in a beaker of distilled water. Leave overnight to wash away excess dye. Next day place eight labelled boiling tubes each containing 5 cm 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. Decant the liquid into a second boiling tube or remove beetroot sections using a technique that does not squeeze the slice e.g. spear with a pointed seeker. Shaker the water/solution to disperse the dye. Switch on the colorimeter and set it to read % absorbance.
Set the filter dial to the blue/green filter.
Using a pipette accurately, measure 2 cm distilled water into a cuvette. Place the cuvette into the colorimeter, making sure that the light is shining through the smooth sides. Adjust the colorimeter to read 0 absorbance for clear water. Do not alter the setting again during the experiment. Place 2 cm of the dye solution into the colorimeter cuvette and take the reading for the absorbency. Repeat the readings for all the temperatures. Present results in an appropriate way.
Identify any trends or patterns in your results.
The variables kept constant
The same diameter corer is used so to keep the surface area of each beetroot piece the same size.
The dependant variable was temperature since it was altered in each experiment.
When the beetroot has been cut some of the cell membranes is broken, which means some anthocyanin will leak out. This must be completely washed off in order to maintain the reliability of the results.
I will use distilled water to so that I have a reliable substance to test with a colorimeter. Excess dye was washed out overnight to ensure more accurate and fair results.
Reading of colorimeter was set as...
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