Baking

Why it works

A batter or dough enters the oven as a loose suspension of flour, water, fat, sugar, air and whatever is making gas. Heat acts on all of it at once but on different schedules, and that sequence is the mechanism.

Gases expand first: trapped air, carbon dioxide from a chemical leavener or from yeast, and — much the largest contributor by volume — steam from the water already in the mixture. Fat melts at the same time, so things briefly get looser, which is why a cake spreads before it climbs.

Then structure catches up. Starch granules absorb water and swell somewhere around 60–85 °C, and egg and gluten proteins coagulate over a broadly similar range. Once they set, expansion stops and the shape is fixed.

Baking works when those two schedules overlap correctly — the mixture staying soft long enough to rise, then setting before its own gas pressure outruns the structure holding it. Most baking failures are that window missed in one direction or the other.

Browning is separate and later. The surface dries, and once it is hot enough, meaningfully above roughly 140 °C, Maillard reactions between sugars and proteins and caramelisation of the sugars themselves give the crust its colour and much of its flavour.

Key variables

• Temperature, which trades lift against evenness. Hotter sets the outside sooner: more spring, darker crust, more risk of a raw middle. Cooler bakes evenly and dries things out.
• Whether the oven is telling the truth. Dials are often out by a noticeable margin — worth checking with a separate thermometer before blaming a recipe. Fan ovens run effectively hotter; the usual correction is around 20 °C down.
• Tin material and colour. Dark metal absorbs radiant heat and browns bases faster. Glass and ceramic are slow to warm and then hold heat, so they carry on cooking after coming out.
• Doneness cues over stated times. A skewer coming out clean, edges just pulling from the tin, a top that springs back. Bread is judged more reliably by internal temperature, in the region of 93–99 °C.
• Early steam. A moist surface stays pliable and can keep expanding; letting it dry too soon caps the rise.

What goes wrong

• Sunk middle → the structure set before it could carry itself, or was disturbed while still soft → usually too much leavener, an oven cooler than it claims, or the door opened in the first two-thirds. Check the temperature before adjusting the recipe, and leave the door shut.
• Dark outside, raw inside → oven too hot, so the crust browned and set long before the centre reached setting temperature → drop it 15–20 °C and give it longer, tenting with foil once the top is where you want it.
• Dense and pale → too cool, or a chemical leavener past its usefulness → baking powder degrades on the shelf and is worth replacing rather than trusting.
• Uneven browning → every oven has hot spots → rotate once, after the structure has set rather than before.

See also

roasting is the near neighbour and the one worth being clear about: the same box doing a different job. creaming and whipping put in the air that baking then sets, and proofing generates it biologically. caramelizing and browning name the surface chemistry described above when it happens outside an oven.