Soft Serve Swirl

You don't need a special blue-spirulina ice cream recipe.

Take your usual vanilla, coconut or other pale soft-serve base and make it exactly as you normally would. Once the mix is chilled and ready for the machine, add the blue.

For a first test, try around 1 g of blue spirulina per kg of mix.

That isn't a magic number. It's somewhere sensible to start. Your base and the blue you're after will decide whether you ultimately use less or more.

Take a little of your chilled mix. You only need enough to mix the powder smoothly.

Add the blue spirulina. Stir or blend until there are no obvious specks.

Mix it back into the full batch. Make sure the colour is even before it goes into the machine.

Freeze as usual. Churn it, run it through your soft-serve machine or freeze according to your normal recipe.

Judge the finished scoop. The colour you care about is the colour of the frozen product, not the liquid mix.

If you want that striking, almost cartoonishly blue soft serve, vanilla is probably the easiest place to start.

A pale vanilla base gives the pigment very little to compete with, and the flavour is strong enough that the blue doesn't need to contribute anything except colour.

Coconut works beautifully for much the same reason.

White chocolate is another obvious candidate.

Once you start adding strawberry, mango, pistachio, chocolate, caramel or other strongly coloured ingredients, you're mixing colours rather than simply turning a white base blue. That can still look great. Just don't expect every flavour to produce the same blue.

You don't have to colour the whole batch.

Make a more intensely coloured portion of your base and fold or ripple it through an uncoloured one. You can go from a faint blue marble all the way to a dramatic blue-and-white spiral.

For a shop already selling vanilla soft serve, this can be considerably easier than developing an entirely separate blue flavour.

And visually, the contrast may be better than making everything uniformly blue.

They can absolutely work, but don't choose them expecting them to behave exactly like vanilla.

Yogurt is acidic, and fruit brings both its own colour and acidity. That means a blueberry yogurt, mango sorbet and vanilla gelato can all look completely different with the same amount of blue spirulina.

Taste the dessert first. Make the colour work around the flavour, not the other way around.

If you're specifically chasing a very clean vivid blue, start with vanilla or coconut.

The maths is pleasantly boring.

At a 1 g/kg starting point: 1 kg mix -> 1 g blue spirulina; 5 kg mix -> 5 g; 10 kg mix -> 10 g.

Once you've tested your own base and decided that, say, 0.8 g/kg gives you exactly the blue you want, use that instead.

That's your recipe.

It's too pale: judge it after freezing first. If it genuinely needs more colour, increase the dose a little on the next test.

There are blue specks: the powder wasn't fully dispersed before it went into the mix. Mix it into a small amount of the chilled base first.

It isn't the same blue as the photograph: that's normal. Milk solids, fat, vanilla, fruit, acidity and the natural colour of your base all affect what you see.

It looked better before freezing: frozen desserts scatter a lot of light, so a finished scoop can look softer or more pastel than the liquid mix. Develop the colour against the finished frozen product.

Blue is the visual hook. The soft serve still has to taste good.

Vanilla-blue doesn't need to become spirulina flavour. Coconut doesn't need extra blue simply because more pigment is available.

Get the flavour right, add enough blue to make people look twice, and stop.

Let the colour sell the scoop before anyone reads the flavour.