Acid phosphate

Popping up as an ingredient on menus worldwide, acid phosphate has officially been reborn after disappearing from sight for nearly 70 years. But what is it?

Made originally in 1868 as an invigorating health tonic, acid phosphate is basically a neutralised solution where calcium, magnesium salts and potassium and used to 'dial back' the acidity of phosphoric acid. Once the reactions between the ingredients are finished it levels out at a pH between 2.2 and 2.4 (in comparison this is slightly higher than freshly squeezed lime juice at pH 1.9.)

It was used in the days of soda fountains when the soda jerks would mix lemon oils with acid phosphate to make lemon soda - it became fashionable during times when actual lemons were hard to come by - and has since become popular again with a new generation of bartenders who are making their own flavoured sodas. It was also an ingredient previously used in the original Coca-Cola formula, although that has now been replaced with phosphoric acid.

What does it taste like?
Acid phosphate is best described as adding a detectable sourness without bringing any other particular tastes to the table- unlike lemon or lime juice, say - therefore it won't otherwise influence the flavour of a drink and bartenders can find it a useful alternative to balancing out sweetness. A 250ml bottle of acid phosphate is enough to influence the taste of between 50 and 100 drinks.