Ask the Chef: Why Does Coconut Oil Pop and Explode in the Microwave?

We're debuting a feature we'll do periodically called Ask the Chef, where we handle your burning questions, the ones that drive you crazy in the kitchen. We've partnered with Matthew Robinson, a chef with not only kitchen experience but product development chops and lots of food science knowledge to boot. His mojo is to inspire people to innovate in the kitchen. You can find him at the Culinary Exchange.  Or right here! 

Q: Why does coconut oil pop and explode when I try to melt it in the microwave? 

The short answer to this burning question (which it turns out is more of a steaming question) is…water. Water? Yes, water. You might be thinking "Wait! Coconut oil is, well, oil not water." But it's true, and here's why.

This issue has as much to do with the coconut oil as it does the microwave oven. I am going to make a guess that most folks use cold pressed coconut oil. And why wouldn’t you? It is less refined and no chemicals are added to process it. It is basically what is left after coconut meat has the Dickens pressed out of it.  However, even if that coconut has been dehydrated, there will still be moisture in the mix. Water can be sticky stuff and without further refinement, it will be present in the coconut oil. This maybe unintentional, but it is there.

Now, the microwave part. First, here is something interesting to know (not really important to daily living, but important for this story): fat and water have a positively charged side and a negatively charged side.  Microwaves like to excite molecules that have both a positive side and a negative side; in fact, it makes these molecules spin and twist around and that is how a microwave heats foods up. But, here is the rub. (Get it ? Molecule rubbing together!) For reasons relating to the physics of the world we live in and maybe the theory of relativity and possibly even some quantum mechanics and string theory (or just water’s di-electric constant), microwaves are good at heating water. In fact, if there is one thing a microwave is better at than practically anything else, it is heating water. 

The popping that happens when coconut oil is microwaved is that trapped water is being turned to steam and popping out excitedly. Perhaps you have experienced the same issue when melting butter in the microwave. Butter, an emulsion of fat and water, will do the same thing. The water heats more rapidly than the fat, is turned to steam and pops as it breaks through the emulsion.  Another example of water popping out like this is in the making of popcorn. A small bit of water resides in each kernel with the starch. When heated, the water steams, expands, forces the kernel to pop open and instantly gelatinizes the starch into that puffy deliciousness that is popcorn. If you heat a fully refined fat that contains no water, there will be no popping.

How might this popping be resolved? Microwave on a lower setting, stirring often, heating the oil slowly and, for the sake of saving clean up time, put a microwave safe cover on the dish! 

Thanks, Chef! Got a burning question, something you can't really figure out and want access to your own personal Kitchen Wizard? Well, Chef Matthew is the next best thing. Send me your burning questions and we'll start a queue for him to tackle.