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Popping Your Beliefs, One Candy at a Time

by Bruno Van de Casteele

April 26, 2015

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Donate In my previous post (yes, the one about Playboy), I mentioned that it is sometimes good to challenge yourself on things you consider "facts" or where you assume something to be the way it is. It is a fun skeptical exercise that keeps you on your toes. Consider it the sort of skeptical antitheses of the Queen in Alice in Wonderland... unbelieving six things before breakfast.

Take for instance the carbonated candy that pops and fizzes when you put it in your mouth. In the States it started as "Pop Rocks," but it has been marketed under several brands since the 1980s by General Foods (later Kraft Foods). This year it made an appearance in the chocolate eggs for Easter. I've eaten it before, mostly in the context of modern cooking (see my post on Cooking for Geeks) and I had always assumed it was some sort of weird chemical, reacting with the saliva in your mouth. My friend Helmut challenged me to find out if that was true and, if so, which chemical. As it turns out, it's not some special industrial chemical, and although there is indeed chemistry involved, Pop Rocks mainly pop because of physics.

As described in one patent, it is fairly straightforward to make this candy. Melted sugar (syrup, but not caramelized, at 138C) is "gasified at superatmospheric pressure," according to the patent, in a range of 500-700 pounds per square inch (34-48 bar) and in the presence of CO. The mixture is then cooled and "bubbles of gas are entrapped in the solidified sugar. After the melt has solidified, the pressure is released, which fractures the sugary mass into granulated pieces of a variety of sizes." That also explains why the candy is irregular shaped, looking like "pieces of gravel."

It is indeed as simple as that—no complicated chemicals involved. When you eat it, the candy melts in contact with your saliva and releases the highly-pressurized pockets of CO. That creates a short-lived but entertaining popping sensation (although I have to say that the novelty wears off really quickly).

There's also an urban legend linked to this, namely of kids dying when eating a lot of this candy and then immediately drinking a soda. That would result in too much carbon gas in the stomach, making it explode. Snopes has debunked this claim very well, but notes that it still pops up from time to time, although modernized now with Mentos and Coke. You can check YouTube for a lot of silly things around this persisting claim, such as this video:

In conclusion, that was an interesting challenge by my friend. I was wrong, I learned something new and it gave me another dinner-conversation topic. But even if I was correct, it would not have been time wasted, as it would have solidified my understanding of an unexamined belief with more correct information. It's always a good thing to check on your own beliefs. Maybe not six before breakfast, but at least one per day—that's what I recommend.

by Bruno Van de Casteele

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