How much blue spirulina should you use?

Blue spirulina can look incredibly intense in a glass of water and surprisingly subtle once it goes into a finished recipe.

Milk, oat milk, coconut milk, ice cream and frosting all soften the colour to some degree. Ingredients such as coffee, cocoa, caramel and strongly coloured botanical extracts can overpower it very quickly.

So when you’re figuring out your dose, skip the water test and make a small batch of the actual product instead.

For a pale drink, around 1 g per litre is a sensible first trial. For ice cream, gelato or soft serve, try around 1 g per kg of mix. For concentrated applications such as frosting and glaze, 0.1 g per 100 g gives you an easy starting point.

From there, simply add more or less depending on the blue you want.

Blue spirulina is much easier to work with if you don't add the dry powder directly to a full batch.

Take a small amount of cold water or some of your liquid base and mix the powder into it first. Once you have a smooth, intensely blue liquid, stir that back into the rest of the batch.

This makes it easier to get an even colour without chasing little pockets of powder around your drink or mix.

This is particularly important with frozen desserts and anything involving heat.

The blue you see in an ice cream mix isn't necessarily the blue you'll see once it has been churned and frozen. Likewise, if you're making a glaze or another heated product, add the blue spirulina as late as your recipe allows and judge the colour once the product has cooled.

Acidic recipes also deserve a test batch. Phycocyanin—the natural blue pigment in blue spirulina—is sensitive to its environment, so a recipe's acidity can affect both the shade and its stability.

If 0.8 g/L gives your signature lemonade exactly the blue you want, that's now your recipe.

Don't turn it back into “roughly half a teaspoon.”

Record the amount in grams per litre or grams per kilogram and use the same ratio when you scale up. It makes the difference between a drink that's the same blue every Friday and one that depends on whoever happens to be behind the bar.

And if you're moving from a small trial to a much larger production batch, make one intermediate batch first. It's a cheap way to catch differences in mixing, temperature or processing before committing the whole lot.