Why You Should Never Carbonate Milk

So you have a SodaStream Sparkling Water Maker or similar carbonation machine sitting on your kitchen counter: You know that you can add some sparkle to your water with it, but you may be wondering about other liquids, since some people think carbonation makes drinks taste better. Sparkling juice works great, and you can even make sparkling wine with a SodaStream (although sparkling red may be an acquired taste for some). Cold brew is also fine, as long as it's black. Just don't think about running milk through your carbonation machine.

This isn't really a question of taste — the idea of a fatty drink turned sparkling may not appeal to many, but hey, some people are curious, and that's understandable. YouTuber Joe Barnard was one such person, and he ran into problems before he even tasted any sparkling milk. When he tries it, the SodaStream makes a concerningly long gurgling noise before the milk seeps out the top of the bottle and makes a mess on his table. The milk spatters even more when he removes the bottle (and he slightly underfilled the SodaStream bottle, too). Other videoed attempts show pretty much the same result.

As for the taste of the carbonated milk, Barnard found it unpleasant, to say the least. Other sources suggest that the taste is typically sour because of the way sugars react with carbon dioxide. The proteins and fats in milk don't play well with carbon dioxide, either: The proteins undergo a process called denaturing when injected with CO2, resulting in an unappetizing curdling effect to go along with that sour flavor.

Another problem with carbonating milk is that cold liquids don't carbonate so well, as they can't absorb as much carbon dioxide. This may lead some people to consider just leaving their milk to come to room temperature before carbonating it. This would likely just add a food safety concern to a very messy experiment, since it's unsafe to leave milk out for more than two hours (it should really be kept around 37 degrees Fahrenheit), making this an unnecessary extra risk for little payoff.

You may be wondering if this rule applies to just dairy milk, or if milk alternatives like oat or soy milk also carbonate badly. There's not much evidence beyond the occasional YouTuber or Redditor who tries this, and the results seem similar to dairy milk. There isn't reliable scientific commentary on why this is the case. However, if fats and proteins are key parts of the reason why dairy milk carbonates poorly, then it's probably a similar reaction. This is because non-dairy milks are often made of fat emulsified in water (although it's vegetable oil instead of dairy fat). That said, non-dairy milk proteins do react differently to dairy milk in other settings, like if you try to steam them for a latte — there's definitely room for a budding food scientist to experiment more. But overall, any milk in the SodaStream is probably a bad idea.