Food and Drink Colour

The chemistry behind the colour of food: the pigments plants and animals make, what cooking, acidity and oxygen do to them, how the colour of coffee, beer, wine, tea, honey, maple syrup and spices is measured and graded, and what the evidence says about colour and appetite.

Colour is never sufficient evidence that food is safe or spoiled; pages say so where it matters. No health claims are made about colourants.

19 topics · 95 evidence-labelled claims · 62 sources

Tools

Food and drink colour scales

Food pigments

Chlorophyll, carotenoids, anthocyanins, betalains and myoglobin.

Why do green vegetables turn olive-grey when you cook them?Cooking pushes chlorophyll to lose the magnesium atom at the centre of its ring.Why do carrots, tomatoes and salmon stay coloured after cooking?Their colour comes from carotenoids — long, fat-soluble molecules whose chain of alternating double bonds absorbs blue and violet…Why does red cabbage turn blue, purple or pink depending on what you add?Red cabbage, blueberries, blackcurrants and red grapes are coloured by anthocyanins, water-soluble pigments whose structure chang…What makes beetroot red, and why does it behave differently from red cabbage?Beetroot, chard stems, amaranth and prickly pear owe their red-violet and yellow-orange colours to betalains, nitrogen-containing…Why is raw meat red, purple or brown, and why can't colour tell you when it is cooked?Raw meat's colour comes mainly from myoglobin, and depends on what is bound to its iron: purple deoxymyoglobin without oxygen (in…

What cooking does

Browning, oxidation and pH.

What is the Maillard reaction, and why does it make food brown?The Maillard reaction is a cascade between reducing sugars and amino groups from proteins or amino acids that produces brown poly…What happens to sugar when it caramelises, and how is caramel colour made?Caramelisation is sugar breaking down under heat on its own, without the amino groups the Maillard reaction needs.Why do cut apples, avocados and potatoes turn brown, and how do you stop it?Cutting breaks cells and lets polyphenol oxidase (PPO), an enzyme kept apart from the fruit's phenolic compounds, meet them in th…Can you tell if food is ripe, fresh or safe from its colour?Colour is a good guide to ripeness in many fruits, because ripening replaces chlorophyll with carotenoids or anthocyanins on a fa…What are food colourings, and what do E numbers and FD&C names mean?Food colourants are additives used to restore colour lost in processing, even out natural variation or colour foods that would ot…

Drinks and grading scales

Coffee, beer, wine, tea, honey, maple syrup and spices.

How is coffee roast colour measured, and what do light, medium and dark actually mean?Roast colour is measured by reflecting light off ground or whole beans and reporting a number — most often on the Agtron Gourmet…What do SRM and EBC beer colour numbers mean, and how do they convert?SRM and EBC both measure how much deep-blue light at 430 nm a centimetre of beer absorbs, then multiply by a factor: 12.Why do red wines turn brick-coloured and white wines turn golden as they age?Young red wine gets its purple-red from grape-skin anthocyanins.Why is black tea red-brown and green tea pale yellow-green?Both come from the same leaf.How is honey colour graded, and does darker honey mean lower quality?In the US, honey colour is designated in seven classes from Water White to Dark Amber, with equivalent ranges on the Pfund scale…Why does chocolate go white or grey on the surface?The pale film is bloom, and there are two kinds.What do the colour classes of maple syrup mean, and why is some syrup darker?In the United States, Grade A maple syrup is sold in four colour classes — Golden, Amber, Dark and Very Dark — set by how much li…How is the colour of paprika and saffron measured and graded?Both are graded on the colour that can be drawn out of the spice, not on how the powder or threads look.

How food looks

Appetite, freshness cues, plating, lighting and photography.

What makes the colour of food look appetising?Food looks appetising when its colour matches what experience says that particular food looks like when it is fresh, ripe or prop…