Yes. Blue spirulina is sensitive to acidity, which is worth knowing if you're making lemonades, cocktails, fruit drinks, yogurt, sour candy or anything else with a low pH. That doesn't mean you can't use it with acidic ingredients. It just means you should test the colour in the finished recipe.
What actually happens?
The blue in blue spirulina comes from phycocyanin, a naturally occurring pigment that is sensitive to its surroundings.
In water, milk and other relatively neutral, pale bases, it can produce a very clean blue. Add lemon juice, lime juice or another acidic ingredient and the colour can change — sometimes becoming more blue-green, sometimes simply becoming less vivid as conditions become harsher.
How noticeable that is depends on the recipe.
A lightly acidic drink with a small squeeze of citrus is very different from a concentrated sour mix. Temperature, storage time and the other ingredients in the recipe matter too.
Can I make blue lemonade?
Absolutely.
Just don't develop the colour in water and add the lemon afterwards.
Make a small batch of the actual lemonade, including the amount of lemon, sugar and other ingredients you intend to use. Then add your blue spirulina and judge the result.
You may get a bright aquatic blue, a turquoise shade or something softer depending on the recipe. If you like the colour, that's your colour — there is no requirement that every blue spirulina drink has to look royal blue.
The same applies to lime sodas, cocktails and mocktails. In fact, some of the most interesting colours you can get from blue spirulina come from deliberately working with the recipe rather than fighting it.
What if I need a very specific blue?
Then pH becomes something worth paying attention to.
Once you've made a version you like, record the recipe and, if you have a pH meter, its finished pH. That gives you something concrete to reproduce when you make the next batch.
For layered drinks, you can also play with keeping acidic and less-acidic components separate until serving. Apart from protecting the colour for longer, the contrast can become part of the presentation.
Don't forget about time
The colour you see immediately after mixing isn't necessarily the colour you'll have several hours or days later.
If you're serving a drink immediately at a bar, a quick test may be enough. If you're bottling something in the morning to sell throughout the day — or developing a packaged beverage with a meaningful shelf life — test it over the actual amount of time you expect it to sit.
That's much more useful than asking whether blue spirulina “works with acid” in the abstract.
It does.
The question is whether it gives you the colour and stability you want in your particular recipe.
FAQ
Does blue spirulina work with acid?
Yes, but acid can change the shade and stability. Test the finished recipe with the actual acid level, storage time and serving conditions, then record the version you approve.