Devise and carry out experiments to investigate the effect on the colour of cooked vegetables of adding
salt (sodium chloride) and sodium bicarbonate (sodium hydrogencarbonate) to the cooking water. There
are many variables involved including concentration of additives, cooking time and type of vegetable.
Peas or green beans are convenient to use because they can be cooked in small quantities and they have
a relatively uniform colour. You will have to assess any colour changes with the naked eye and this will
inevitably be subjective. Colour assessment could be made more objective by (a) using a tester who is
not aware of how each sample has been treated and/or (b) using an ‘odd one out’ test. Here a tester is
offered three samples to assess, one cooked in one way and two cooked in another, and asked to pick
the odd one out.