| Date | May 2009 | Marks available | 2 | Reference code | 09M.3.sl.TZ1.F1 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | F1 | Adapted from | N/A |
Question
Artificial food colourants have recently been linked to increased hyperactivity in children. Many foods are colourful because of the natural pigments they contain.
Explain why naturally-occurring pigments are coloured.
State the class of pigments that give carrots and tomatoes their colour.
Outline why this class of pigment is susceptible to oxidation, and the effect of oxidation on this pigment.
Markscheme
(ability to) reflect and absorb different wavelengths/frequencies/colours of visible light;
carotenoids;
Do not accept \(\beta \)–carotene.
presence of (multiple) carbon–carbon double bonds;
loss/bleaching of colour / loss of vitamin A activity / off odours;
Do not accept change of colour.
Examiners report
Part (a) was generally poorly answered. Many candidates found it difficult to explain why naturally occurring pigments are coloured in terms of their ability to absorb and reflect light.
Candidates commonly correctly stated anthocyanins as the pigments in cranberries and strawberries, but they mistakenly gave \(\beta \)-carotene or carotenes as the answer for (c) (i) instead of the name of the class of pigments, carotenoids.
Only the better candidates readily understood the connection of the carbon-carbon double bond to oxidation and its relationship to the colour of the pigment.
