Blue spirulina can handle some warmth, but it isn't a colour you want to cook for longer than necessary. The blue comes from phycocyanin, a natural pigment that is sensitive to prolonged heat. As a general rule, the later you can add blue spirulina to a recipe, the better your chances of keeping a bright blue. That makes it particularly easy to use in cold drinks, ice cream, frosting, glazes and other recipes where the colour can go in towards the end.
Can you use blue spirulina in hot drinks?
Yes — but there's a difference between adding blue spirulina to a drink that's hot when served and actually cooking it.
For a blue latte, for example, you don't need to boil the powder with the milk. Make the drink as usual and mix your blue spirulina in towards the end.
If you're developing a café recipe, try it at the temperature you actually serve your drinks. If the colour looks good and holds for the time between making and drinking it, that's far more relevant than whether the ingredient can theoretically survive an hour at the same temperature.
What about baking?
This is where blue spirulina becomes more difficult.
An oven gives the pigment both relatively high temperatures and plenty of time at those temperatures. You shouldn't expect the brilliant blue you see in the raw batter to necessarily survive unchanged through baking.
If the blue is important to the finished look, consider putting it somewhere that doesn't need to spend half an hour in the oven.
Think buttercream, icing, glaze, cream, filling or decoration rather than the cake itself.
You can certainly experiment with blue doughs and batters, but make a small test before committing to a production batch.
For glazes, syrups and dessert bases, add it later
If your recipe has a cooking stage, there's usually no reason for the blue spirulina to be there for all of it.
Cook your syrup or dessert base first. Once the hot stage is finished and the mixture has cooled sufficiently for the rest of your process, add your blue spirulina.
The same approach works particularly well with glazes and frostings: make the base first, then introduce the colour.
You'll generally get a brighter result and you can see the final colour as you adjust it.
Heat isn't the only thing happening in a recipe
A hot lemon syrup is a more difficult environment for phycocyanin than warm milk.
That's because temperature isn't acting in isolation. Acidity, time and the other ingredients in the recipe all affect how well the colour holds.
You don't need to model all of those variables. You just need to test the process you're actually going to use.
If your café makes a blue syrup once every morning and keeps it chilled for service, make a trial exactly that way. If you're developing gelato, put it through the actual heating, cooling and churning process before deciding whether you're happy with the colour.
How hot is too hot?
There isn't one useful temperature we can give you that separates fine from ruined.
A brief exposure to warmth and a long cooking process aren't equivalent. The recipe's acidity and the length of exposure matter alongside the temperature itself.
So rather than designing a recipe around a supposed maximum temperature, use a simpler rule: don't heat blue spirulina unless you need to, and when you do, keep the exposure as short as your recipe allows.
For everything else, add it after the cooking stage.
The easiest way to use it
If you're making something cold, you're already in blue spirulina's comfort zone.
If you're making something hot, ask whether the colour actually needs to be present during the heating step.
Often, it doesn't.
Make the product first. Add the blue later.
FAQ
Can blue spirulina handle heat?
It can handle some warmth, but prolonged heat can dull the colour. Add it after the hot stage when your recipe allows, and test the finished process rather than relying on a single temperature rule.