Appendix: Some of the Chemical Structures Discussed in the Book
Complex biochemical compounds (generally called ‘organic compounds’ amongst chemistry aficionados) are mainly made of the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and, to a lesser extent, sulphur (S) and phosphorous (P). The myriad of structures that are produced in nature and by the chemical industry arise because C can form four bonds with other elements. In particular, it can bond to itself to form linear chains, chains with branches, and rings (commonly hexagons and pentagons). In theory, an infinite number of structures is possible, but the biochemical pathways found in nature mean that the structures that occur are organised around commonly occurring themes. Examples of some of these can be seen below and in the text.
It is important to note that because C and H are such common elements we tend not to display most of these in the structures, otherwise even quite simple compounds would become hugely complicated. For example, a simple fatty acid looks like this when all the C and H atoms are shown.
The shorthand form shown below, leaving out most of the letters for the C and H atoms, is the convention used throughout chemistry and biochemistry when we draw molecular structures.
Trichloroanisole (TCA) a natural compound that can give wines a musty or corky flavour
Chapter 3
Dimethylpolysiloxane (E900) – an industrial polymer added to vegetable oils to stop foaming during frying
Aniline – the denaturant added to vegetable oil to make it fit for industrial use only
Anilide – formed when industrial vegetable oil is refined to remove aniline
Pyropheophytin A (PPP) – a degradation product of chlorophyll, the compound that gives olive oil its green tinge
Chapter 4
Malachite green – an effective treatment for fish diseases, but risks to human health mean it’s banned for use in aquaculture in many countries
Sodium tripolyphosphate (TPP) – used to preserve seafood and, more dishonestly, in the underweighting of seafood
Tetrodotoxin – the toxic compound found in pufferfish
Urea and Melamine – Two industrial products high in nitrogen and added to fake milk and baby formula to fool simple protein tests
β-carotene – the main natural yellow-orange pigment occurring in cheese
Bixin – the orange pigment found in annatto (E160b), used to colour cheese and cheese substitutes
Chapter 7
Auramine O – used as a stain for some types of bacteria in microbiology, but found as an adulterant in ground coriander
Sudan Red – Sudan dyes are used to colour waxes, oils, solvents and polishes, but have also been used to colour ground spices such as curry and chili powders
Vanillin – the compound behind the flavour and smell of natural vanilla, which is commercially synthesised to meet demand from the food and beverage industry
Cinnamaldehyde – the principal component of cinnamon
Chapter 8
Di(2-ethylhexyl) phthalate and diisononyl phthalate – phtahlates used to increase the flexibility of plastics, such as PVC, but found being added to jams, sports drinks and fruit juices to make them appear more cloudy and therefore more natural
Diethylene glycol – a component of antifreeze, but illegally used to sweeten wine
Chapter 9
Formaldehyde – a naturally occurring compound with many industrial uses, but widely known as a tissue fixative and embalming agent, which is why it has been used to help preserve fruits and vegetables
Chapter 10
(Z)-8-tetradecenal – humans are particularly good at detecting this aromatic compound, which gives citrus its characteristic odour
Ethyl methylphenylglycidate – the compound responsible for artificial strawberry flavours