| Date | November 2011 | Marks available | 2 | Reference code | 11N.3.hl.TZ0.F6 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | F6 | Adapted from | N/A |
Question
A food product is often judged simply by its colour. Natural pigments that give rise to food colour include anthocyanins, carotenes, chlorophyll and heme. The structures of these pigments are shown in Table 22 of the Data Booklet.
Explain why these natural pigments are coloured.
Deduce from their structures whether anthocyanins and carotenes are water-soluble or fat-soluble.
Anthocyanins:
Carotenes:
Markscheme
contain alternate (carbon to carbon) single and double bonds / extensive delocalization/conjugation/\(\pi \) bonding;
absorb in the visible region and transmit complementary colour;
Anthocyanins:
water soluble;
Carotenes:
fat soluble;
Examiners report
Candidates could not relate the length of conjugation with absorption in the UV/Visible spectrum.
Many were able to deduce the water or fat-solubity of the two natural pigments given.
