What Common Gas Do Swiss Cheese and Pop Rocks Have in Common?



Carbon dioxide is a common gas that we breathe out but plants breathe in, helping them to grow. It’s also a key player in creating the holes in Swiss cheese and putting the “pop” in Pop Rocks. Here’s stuff you probably didn’t know about cheese and candy.

The holes in Swiss cheese are officially known as “eyes.” The first step in their formation happens when the bacteria that turn milk into cheese emit a chemical compound called lactic acid, or milk acid. Then, other bacteria called Propionibacteria shermanii or P. shermanii eat the lactic acid and burp out lots of carbon dioxide gas.

Did you know that the U.S. Department of Agriculture has rules about how big the holes can be? In 2002, the department caused a stir — and inspired a lot of dumb jokes about “hole-y wars” — when it decreed that the eyes in Swiss cheese produced in the States should be about half the size of what was then standard, dropping from about the diameter of a nickel to slightly smaller than the width of a dime.

According to an ABC News report, this wasn’t a random decision: U.S. cheese makers actually asked for the change, because cheese with larger holes tended to break apart in the high-speed slicing machines used by large food-service companies.

Okay, enough about cheese. What about the candy? Here you go: Pop Rocks were invented in 1956, when General Foods chemist William Mitchell was trying to create a powder that would turn into a carbonated drink when mixed with water.  He fused carbon dioxide with hot sugar syrup, but the experiment didn’t work out. One day, some of the sugary powder accidentally got into his mouth and melted, releasing the carbon dioxide and causing it to fizz and pop.

The exploding candy became a fun toy for Mitchell and his food-science pals, but it wasn’t until 1974 that a Canadian branch of General Foods put Pop Rocks on the market. In 1976, when they arrived in the U.S., their popularity … exploded!