The world is a beautiful and bizarre place, isn’t it? For instance, I recently found out that the specks on the outside of strawberries aren’t actually seeds. Then came the fact that slugs have thousands of tiny teeth (yes, really). And now, it seems that without any regard for my sanity or sense of logic at all, it turns out that pistachios sometimes just… burst into flames.
It doesn’t happen often, and your pack of supermarket nibbles almost certainly won’t suddenly explode into flames. Still, though, the news that large amounts of the incendiary ingredient can unexpectedly alight has taken more than its fair share of my group chats’ real estate recently.
So, to save my friends from yet another “fun fact!” round, I thought I’d share the science of the chaotic process with you instead.
Pistachios are basically firelighters
Like so many delicious things, one of the secrets behind pistachios’ tastiness is their high fat levels. The nut is about 45-55% fat and has a low water content ― fat burns incredibly well.
And as per the Transport Information Service (TIS), it’s advised to pack the nuts in extremely dry conditions. If you’re thinking, like I did, that desert-like dryness would increase the chances of the nuts setting aflame, think again; “Fat-cleaving enzymes are activated by the elevated water content,” they say.
This means that the fat decomposes when the nuts become moist, adding more flammable factors, like extra carbon dioxide and heat, into the mix.
They’re also packed in jute bags, and often on heat and pressure-inducing piles of massive amounts. The fibrous kernels are dry and flammable too, leading the TIS to warn that “because of their tendency to self-heat, pistachio nuts may behave like substances from Class 4.2 of the IMDG Code. Excessive stack pressure results in self-heating. Oils which have accumulated in the jute packaging fabric encourage this behaviour.”
FYI, the IMDG code they were talking about is the International Maritime Dangerous Goods Code ― class 4.2 includes “pyrophoric and self-heating substances” such as oily cotton waste and, uh, pistachios.
“This is how a large container of pistachios sitting in a dark, humid room can spontaneously (or not so spontaneously) combust — and why it’s crucial that they be transported under the right conditions, mainly in low temperatures and a dry atmosphere,” Tasting Table said. Oh, good.
It’s not just pistachios, either
The terrifying news continues ― it turns out pistachios aren’t the only nuts that can do this. Culinary Lore debunked the myth that the green goodies are not the only nuts with the capacity to spontaneously combust.
“Any high-fat organic substance may tend to undergo such self-heating during the decomposition processes. If you store enough fresh pistachios in a container, things get very hot as they start to decompose. If conditions are right, they can go up in flames. However, the same is true of sunflower seeds, peanuts, walnuts, cashews, and Brazil nuts,” they say.
Well, that’s certainly information…