Cornflour vs tapioca vs potato starch vs arrowroot
Four pure starches that look identical in the packet and set into visibly different things — and are far more interchangeable in a cake than in a sauce.
The short answer
All four are close to pure starch with the protein, fat and fibre removed, and in a gluten-free flour blend they are far more interchangeable than the internet suggests — they are all there to lighten and to gelatinise, and swapping one for another changes the crumb subtly rather than breaking the bake. In a SAUCE OR A FILLING they are not interchangeable at all, because the differences that barely matter in a crumb are the whole point in a gel: how clear it sets, how firm, whether it survives acid, and whether it survives a long cook. Cornflour is the firm, cloudy, heat-stable default that weakens in acid. Arrowroot sets clearest and handles acid best and thins if held at heat. Tapioca sets glossy and slightly stringy and is the most freeze-tolerant. Potato starch thickens most powerfully at the lowest temperature and breaks down fastest. None of them is flour: they contain no protein, form no network, and substituting one for wheat flour removes structure rather than replacing it.
Where they differ
| Dimension | First | Second |
|---|---|---|
| Set appearance | Cloudy and opaque. | Very glossy, slightly stringy. |
| Set firmness | Firm. | Softer, more elastic. |
| Acid tolerance | Poor — thickening weakens in acidic fillings. | Moderate. |
| Long cooking or vigorous stirring | Tolerates it. | Tolerates it less well. |
| Freeze–thaw | Weeps on thawing. | The most freeze-stable of the four. |
Differences that do not matter
These are real distinctions that are unlikely to change your decision. They are listed so you can stop thinking about them rather than left out so the comparison looks decisive.
- Source. Maize. Cassava root.
- In a gluten-free blend. Lightens; contributes no structure. Lightens; adds chew and browning.
- Protein and gluten. None. None.
Where the differences matter, and where they genuinely do not
This comparison exists because the question is asked constantly and the honest answer depends entirely on what the starch is doing.\n\nIN A GLUTEN-FREE FLOUR BLEND the starches are bulk and lightness. They are all doing the same job by the same mechanism, and substituting one for another at the same weight gives a slightly different crumb and a working bake. Blend recipes that specify one starch precisely are usually reporting a preference rather than a requirement.\n\nIN A SAUCE, CUSTARD OR FRUIT FILLING they are not substitutable without consequence, and the consequences are visible: a glaze that should be transparent turns cloudy, a sharp fruit filling fails to set because the acid weakened the cornflour, a sauce held on the heat thins back out because it was arrowroot.\n\nThe rule of thumb worth carrying: for a clear, acidic, briefly cooked gel use arrowroot; for a firm, forgiving, long-cooked one use cornflour; for anything to be frozen use tapioca.
Potato starch is not potato flour
The two are sold side by side and are entirely different ingredients. Potato STARCH is the extracted starch — white, fine, flavourless, and one of the four compared here. Potato FLOUR is dried whole potato, which is heavy, yellowish, tastes of potato and absorbs a great deal of water.\n\nSubstituting one for the other by weight fails badly in both directions, and the packets are easy to confuse. The same trap exists between coconut flour and coconut powder, and between cornflour in British and American usage.
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A subject of the comparison, so it is reachable from the record a reader is more likely to land on first.
A subject of the comparison, so it is reachable from the record a reader is more likely to land on first.
A subject of the comparison, so it is reachable from the record a reader is more likely to land on first.