Hot Pie On A Cold Day

On last week’s episode, we tried to tackle one of our listener-submitted questions about cold and winter. Specifically:

Why does hot food smell so good as the odors waft out windows on a cold crisp winter day?  Does the cold change the smells to make them stronger?

We didn’t have time to answer this one on the air, but we understand the burning desire for knowledge only quenched by evidence-based scientific data, and we didn’t want to leave you hanging. So here’s what we found:

 

Actually, it probably has more to do with how your brain perceives these smells than it does with the cold day having any affect on those smells.

When you get a whiff of garlic, what you’re smelling are these sulfur-based molecules in the garlic that evaporate into the air at very low temperatures. We call them volatile organic compounds, because they go from being a solid to being a vapor with very little impetus. This is why you can smell garlic that’s just sitting on your counter.

As the temperature of the air drops outside, these volatile organic compounds known as odors, slow down, and there are generally less of them floating about in the ambient air.  So there just isn’t as much to smell out there in winter, and what is out there isn’t nearly as potent.

Increasing heat increases the chance of the molecules escaping into the air, so as you say, cook the garlic, the odor increases. The hotter the air, the faster and farther the odor molecules can travel.  Additionally, increasing humidity traps these odor molecules and allows them to linger.

To help explain this better, imagine conditions opposite to what it’s like outside right now: a hot humid summer day. Ah, the lovely smell of an overflowing garbage can in the park on this staunchy afternoon. It’s pretty gross isn’t it? And powerful. That’s because odors intensify as the heat increases and as the humidity goes up, and conversely lose their intensity as the air gets cooler and drier.  

Our sense of smell dulls in the cold as well. Neurons called olfactory receptors line your nasal cavity, and are coated in a layer of mucus. Millions and millions of them. Each receptor is tuned to a specific odor molecule. So say, when a molecule of coffee wafts up to your nose, it binds to an olfactory receptor specific to receive and identify it.

The binding triggers the olfactory receptors to send electrical signals that are passed along to the brain, letting you know a sweet sweet hit of caffeine is nearby. When exposed to cold air, these olfactory receptors apparently “bury themselves” a little deeper, and become less sensitive.
So if food smells stronger and better in the winter, you’re probably just perceiving the smell of hot food to be more intense.  Since there are generally less odors just floating around in the winter to get in the way, wouldn’t the odor of the food just sort of…. stands out more.

 

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