Can I use margarine or baking spread instead of butter?

Butter is around 80 per cent fat and 16 per cent water. Baking spreads range from about 75 per cent fat down to 38 per cent for low-fat tubs, and the difference is made up with water. Since water in a batter turns to steam and water in pastry develops gluten, the fat percentage is the single number that predicts whether a substitution will work. The other difference is melting behaviour: butter is hard when cold and melts sharply, while most spreads are soft across a wide range, which matters enormously for anything that depends on solid fat.

What you'll need

• A tub or block with the fat percentage stated

Step by step

1. Read the fat percentage on the tub.It is on the nutrition panel as fat per 100g. Seventy per cent and above is usable in cakes. Below 60 per cent is mostly water and will produce a wet, flat, greasy result whatever you do.
2. Use spread freely in creamed cakes.Victoria sponge, cupcakes, traybakes. A baking spread is already soft, so it creams straight from the fridge and often gives a lighter, more even sponge than butter. It also stays softer when the cake is refrigerated.
3. Do not use it in pastry, shortbread or laminated doughs.All of these depend on solid fat sitting in discrete pieces or sheets. A soft spread smears into the flour immediately, and the extra water develops gluten. The result is tough and greasy at once.
4. Do not use tub spread in buttercream.It will not hold structure and the water makes it slack and prone to splitting. Block butter, or a proper hard vegetable shortening if you need it dairy-free.
5. Accept the flavour trade.Butter carries flavour compounds that spread does not and brings a browning contribution from its milk solids. In a plain sponge you will notice; in a strongly flavoured chocolate, lemon or coffee cake you very often will not.
6. For dairy-free, choose a block, not a tub.Firm block-style vegan butter behaves closest to dairy butter and can be used for pastry and shortbread with reasonable results. Tub spreads cannot.
7. Substitute by weight, one for one.Same weight as the butter the recipe calls for. No other adjustment is needed for a creamed cake.

Tips

• Half butter, half spread is a reasonable compromise in a creamed cake — some butter flavour, and the softer texture spread gives.
• Oil-based cakes are a different tradition, not a substitution: carrot cake, many chocolate cakes and most muffins are designed around liquid fat and are excellent.
• Hard vegetable shortening — the block kind — is very good in pastry and gives a notably short, crumbly result. Half shortening and half butter is a classic shortcrust.
• Check whether the tub says 'suitable for baking'. Manufacturers put that on the higher-fat products and leave it off the ones that will fail.

Common mistakes

• Using a low-fat spread to make a cake healthier — You are adding water, not removing fat from the recipe. The cake comes out flat and wet, and you have to eat more of it to be satisfied.
• Making pastry with a tub spread because it says vegetable fat — The issue is not the source of the fat but its firmness and water content. A soft fat cannot make flaky pastry regardless of what it is made from.

If it doesn't work