Harold McGee embarks on a 10-year 'sniffing expedition' to explore what smell teaches us about our world

Food writer and kitchen scientist Harold McGee says there is a lot to be gained from stopping to smell the roses — and the rotting garbage, too.

"Taste is maybe a half dozen sensations. Smell is countless sensations," he told The Sunday Magazine host Piya Chattopadhyay. "I began to focus on smell as the important element in flavour and then began to wonder why it was that the smells of very different foods can echo each other… that took me on this deep dive into the smells of the world at large."

His latest book, Nose Dive: A Field Guide to the World's Smells, is a culmination of what he describes as a 10-year "sniffing expedition" through the world and through science.

Here is part of their conversation.

As I understand it, what set you off on this particular journey of this book was eating grouse for the first time? 

I was travelling in Europe to find out about avant-garde cooking in the early 2000s … The most memorable, striking experience I had was a very traditional lunch with the centrepiece being grouse — a game bird that happened to be in season at the time — which I'd never tasted before. The taste of it was so powerful, so funky, so meaty, so intense that for a moment I was actually kind of paralyzed. I was having a conversation with my tablemates. I stopped talking and they looked at me as if maybe I was having a stroke. That power to grab everything that my brain was capable of doing and focus on this one particular sensory experience really decided [for] me that I had to learn more about it. 

It was the most intensely meaty flavour, bordering on spoiled, bordering on rotting. That's part of the reason my brain stopped me in my tracks.- Harold McGee

Can you use words to explain what the smell was like?

It was the most intensely meaty flavour, bordering on spoiled, bordering on rotting. That's part of the reason my brain stopped me in my tracks — maybe this is not such a good idea to be eating something like this. But I later learned from talking with my tablemates that, that's exactly what you're looking for in a grouse … When they're shot, they're allowed to sit in a cool room for a few days with the guts still inside to help them develop this very strong, unusual, characteristic flavour. So I was tasting muscle that was working very hard and the result of a process that brings out the essence of animality.

When you ate grouse for the very first time, your brain had no catalogue of what a grouse smells like. So how does your brain deal with not having a catalogue for something?

One of the reasons my brain went into overdrive at that moment was that I thought, well, I'm eating a game bird … pigeon or duck or something like that. That's the flavour that my brain was expecting. When it got something so different, the expectation didn't match the actual data that it was getting. It was that discrepancy that caused it to pause and pay close attention. So it placed the experience in what it knew — the realm of flavourful meats. But it was different enough that it paused and made sure that I was paying attention to the fact that it was different and there might be something wrong with it.

So if our brains rely on previous sensations and experiences, does that mean that smells can be different to different people? We're not all smelling the same thing, right?

That's exactly right … smell is very much a subjective experience. Flavour is not something that's kind of out there in the food or in the world around us. It's actually a sensation or perception that's created in our brains. And all of our brains are different … Sometimes we have emotions associated with those experiences. Other people don't. So it is very much a personal thing. That's why I wanted in this book to put aside the subjective aspect of smell and just say, regardless of whether you're able to perceive this detail or not, these are the things that are out there in the world that can be perceived. And even if you don't perceive them, maybe they're worth looking for.

Is that why some people, for example, find cilantro disgusting or just like it in moderation, and others love it?

Yes, that's exactly right. We think of the smell of cilantro as a very specific kind of unified thing — as if there were molecules of cilantro that we're detecting. In fact, cilantro and everything else in the world is a complex material ... I like to use the analogy of music. Cilantro has a variety of notes that it emits. What we perceive as the chord is what we would think of as the smell of cilantro. What scientists have found is that people who don't like cilantro seem to be especially sensitive to a particular note in that chord, which is a molecule, 10-carbons long, that can be perceived as soapy, like a personal care product rather than something that you actually want to put in your mouth. If that's the note that stands out for you in the chord, then you're not going to like cilantro or you have to work hard to learn to like it.

We as humans don't really play a role in all of that. So we can enjoy the smells of flowers as bystanders. They really have no importance in our life.- Harold McGee

When it comes to flowers, you say that their smell doesn't serve any purpose to us at all. So why are we so drawn to the smell of flowers?

Flowers turn out to be more complicated than I expected. I assumed that flowers have the smells they do in order to attract pollinators, insects that would come and do the work of taking pollen from one flower to another. That's a very important process in nature. It turns out that a number of the molecules that contribute to flowers' smells are not just to attract some insects, but actually to select which insects are attracted and which are not. So some of the molecules actually repel insects that might, instead of just pollinating, start to chomp on the petals or the pollen instead of carrying it from one place to another. Some of the molecules are actually there to repel moulds, yeasts and microbes that would interfere with the life of the flower. But all that's going on in the life of the flower. We as humans don't really play a role in all of that. So we can enjoy the smells of flowers as bystanders. They really have no importance in our life.

You went on a 10-year expedition, sniffing your way around the world to complete this book. What would be the reward for the rest of us if we took more time to just stop and smell the world around us more carefully and more deliberately?

The reward in doing that is to be more fully alive to the world around us … In the last few centuries, as more and more of us have begun living in cities and increasingly homogenized environments, we have less and less to stimulate our sense of smell. We minimize the smells that we ourselves have, clean the air in our offices, in our homes. We fill the air in our home offices and homes with artificial smells. We're letting one of these essential aspects of our lives as animals atrophy. There's a lot to be said for just getting out into the world, breathing deeply, noticing what it is that you're smelling, maybe coming back to A Field Guide to Smells and learning a little bit about why they're there and what they can tell us about the world around us. To me, that just means taking advantage of a sense that we usually don't take advantage of.

Q&A has been edited for length and clarity. Interview produced by Donya Ziaee