The biological formation of a beetroot makes it one of the best subjects for the scientific examination of cell membranes. Beetroot has a deep red or purple colour. This is caused by a pigment held deeply inside the tissue. A covering cell membrane stops the pigment leaking out, according to the Nuffield Foundation. Beetroot is often used in schools as a way to examine the effects of temperature on the tissues of plants.
Beetroot leaks a large amount of its red or purple colour when it is cooked in water at high temperatures, the Nuffield Foundation reports. Many techniques are attempted to reduce the loss of colourful pigment from deep within the beetroot, including not removing a large amount of the skin at either end before cooking the vegetable in boiling water. Damage to the tissue can be measured by the change in colour as it is heated in varying temperatures of heated water.
Five beetroots should be cored to leave a small amount of the centre of the plant. These are left in distilled water overnight. This allows damaged tissues to leak pigment into the water. Individual cells leak colour until they are empty of all pigment, 123 Help Me reports. A single piece of beetroot is placed in water at 20C (68F) for one minute. The beetroot is removed and further pieces of beetroot are placed in water up to 80C (176F). One piece of beetroot is kept as the control for comparison purposes.
When you cut a piece of beetroot you damage the membrane of the tissue covering the cells and pigment leaks out. Heating beetroot damages the tissue and the bonds holding the cell membrane in place. This causes holes to appear in the membrane allowing the release of pigment, Freezing Blue reports. Damage to hydrogen bonds holding each cell wall in place allows the release of a large amount of pigment through the tissue.
Heating beetroot to 20C (68F) releases the pigment containing molecules known as betalain. From 40C (104F) to 60C (140F) the amount of cell damage rises rapidly as the pigment from inside the tissue of the beetroot is released. At 80C (176F) the the betalain release becomes so high the molecules block up the holes in the tissue cell membrane and halt the release of the pigment.