The Old-School Soda Ingredient That Seems To Be Making A Comeback

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Before today's sodas and energy drinks dominated the market, soda fountains were a staple in every neighborhood. When soda fountains slowly fell out of favor, a once-popular ingredient vanished along with them: Acid phosphate. While this seems like an ingredient that would be found in a lab, acid phosphate was once used in soda fountains to give drinks a clean, sharp, sour edge. Although there are old-fashioned sodas that you can still buy today, acid phosphate isn't a common ingredient in these modern-day recipes.

Yet in recent years, thanks to mixologists and craft soda makers, acid phosphate seems to be making its way back into the spotlight. Unlike some of the favorite discontinued sodas that won't see the light of day, acid phosphate is once again being recognized for its ability to provide a pure sour flavor. For starters, consider the potential the vintage ingredient has in cocktails. Lemon, lime, and other citrus juices are one of the most universal ingredients in a cocktail recipe — while this is tried and true, acid phosphate brings a competitive edge. Everyone can more or less pick out the presence of citrus, but the unique tart, clean, yet flavorless mouthfeel? Drinking a cocktail with acid phosphate will be a novel experience for most.

In the era of super sugary drinks and sodas, acid phosphate can help cut down on over-the-top sweetness and bring some much-needed balance. You probably wouldn't want to add more lemon to a sugary lemonade — but a dash of acid phosphate can be the perfect solution. Retro soda shops scattered throughout the country have this ingredient on the menu, like Soda Fountain in St. Louis, Missouri, and Kast Iron Soda Works in Salem, Ohio.

Soda fountains served as a cool hangout spot, much like a bar, but instead of hard drinks, patrons sipped on whimsical creations like egg creams, malted shakes, and sodas of all flavors. While the modern-day soda features cheap ingredients like sugar syrups and artificial flavors, pharmacists at soda fountains actually whipped up ingredients that were said to be medicinal. Some "healing" ingredients were wild — like cocaine or opiates — to remedy headaches, while others, such as acid phosphate, were thought to boost energy. Phosphorus is an abundant mineral that can help the human body. This is likely where many of the health claims for boosting energy and longevity came from. 

In fact, acid phosphate worked well to replace citrus juice because it's a shelf-stable way to provide acidity. In the late 19th and early 20th centuries, a popular soda fountain order may have been something like a cherry, lemon, or chocolate phosphate soda, which was part syrup, carbonated water, and just a dash of acid phosphate. Another retro soda made use of the acid, the Japanese thirst quencher, which also featured grape juice, orgeat syrup, bitters, and club soda. You can be part of the acid phosphate revival, too, and buy a food-grade bottle like MacSweetie's Acid Phosphate. (Be aware — acid phosphate is not the same as phosphoric acid, which is not a safe substitute, as the former has been buffered with mineral salts.)