Subway: What the Hell Is That Smell?

Subway has a one-of-a-kind smell. It’s that sweet, herby, bready scent that wafts in such pungent clouds that you don’t even need to go inside a store to smell it. Just walking past a Subway is enough. You’ll be strolling down a footpath when suddenly you’ll find yourself feeling disgusted or hungry, depending on how you feel about Subway.

But what is it? Seriously, what exactly is going on in Subway that makes that smell? Is it their bread? Their Salami? Do they have Subway-flavoured Ambi Pur fresheners that squirt the scent into the air? Just what the fuck are they doing?

After years of wondering, I decided to find out.

I started by emailing Subway's headquarters and asking "what's the smell in your shops?" At first, Subway seemed an incredibly polite corporation and I received a reply telling me “no problem, I can get you a few lines.” But they then proceeded to ghost me for the next three months. In total, I emailed 12 times and never once received an actual response.

Realising they were going to play hard-ball, I decided to cold call 100 of their restaurants to ask individual franchisees about the origin of Subway’s smell. This survey took two full workdays to complete, and I got a variety of responses. Some people giggled throughout the convo, while others told me the info was confidential. One employee just hung up before I could even ask.

Overall, 78 percent of the restaurants either didn’t pick up the phone or didn't answer the question. Eleven employees, however, blamed the smell on their bread. A further nine people thought the aroma was a mixture of subs and cookies; one respondent said the chicken created the scent; while another worker believed the stores’ sauces and marinated meats were to blame.

So, I’d established that 78 percent of all Subway franchisees get cagey on the phone or didn't answer, and a remaining 22 percent don’t agree on what produces their own iconic smell. I still needed to discover the truth.

My next step was to hit up my local Subway restaurant and ask them for some raw dough. I wanted to bake their food in my kitchen and see if I could recreate the smell in isolation. But alas, every single Subway employee rejected my request. One employee even glanced at their oven like it was overflowing with treasure, before mumbling “no.” It was as if the employees wanted their smell to remain a secret.

I was hot on the trail, and I knew it.

Something Subway employees don’t seem to realise is that a recipe for recreating their bread is publicly available on Recipe Community, while a Sub cookie recipe is on All Recipes. To ensure I was recreating Subway’s actual products, I cross-checked the recipes with Subways’ ingredient list, made a couple of tweaks, and then set out to produce a variety of Subway doughs.

On a dreary Sunday morning, I started making four different types of Subway bread. I knew that recreating their food and scent would be difficult—mainly because I hate baking. Also, my kitchen smelled like reheated Chinese takeaway. Above all though, this would be a vexing endurance test, as I planned on producing mass batches of rolls and Subway cookies the following day as well. All told it would be 48 hours of Subway cookery.

At first the dough didn’t smell like Subway, but as I sprinkled some Italian herbs onto a roll, my house began to take on a slightly Sub-y odour. This fragrance intensified as I placed the loaf into the oven. It was close but… somehow still not quite right. My Subway bouquet still needed a tinge of sweetness. I ate my mediocre buns in defeat.

The next day I was semi-ready to make the same breads again, along with five different types of cookies to see if the smell was a composite. I’d also cleaned my kitchen that morning, so the smell started out like an Ajax commercial before slowly morphing into a wholesome bakery.

Then, suddenly, just when I began whipping up my cookie batter, the house’s scent mutated again—and it smelled exactly like 4PM outside a suburban Subway store. As my oven began blasting the combined scent of basil and macadamia cookies I knew I'd done it. I was ecstatic: I’d done it.

Subway’s smell is—wait for it—the bread and cookies baking together!

That might not seem like a huge shock, but it is also an incomplete answer. I still hadn’t isolated the exact chemicals in question.

After a bit of digging, I worked out that I’d need a flavour chemist to help me get this info, so I called the CSIRO’s food innovation centre to ask them if I could chat with one of their scientists. To my absolute delight, they said yes.

The CSIRO’s food innovation centre is a rad facility that works with the Aussie food and bev industry. According to this snazzy YouTube video, they help companies make safer, fresher, and healthier foods. They also have the tech to identify the specific compounds wafting from Subway's doors.

This man is a flavour chemist by the name of Dr Tanoj Singh and he agreed to help me out. Dr Singh said he’d use a probe, commonly known as solid-phase microextraction fibre, to analyse Subway’s smell. You can see this pen-like device in the above photo. It has a variety of odour-absorbing chemicals coating its point and when the tool is exposed to the air, the aroma compounds bind to the tip.

After the probe had collected Subway’s aroma from outside a store in Werribee, Dr Singh told me he’d take it back to his lab and use a technique called gas chromatography-mass spectrometry (GC-MS) to analyse the chemicals on the gadget. This method basically takes the chemicals from the device’s tip, separates them, and puts the info on a graph. Dr Singh said the chart would tell us “what chemicals came off this probe, and how much was there.”

Four weeks later, I received the chef’s kiss of emails. The CSIRO had sent me some pictures and videos from Dr Singh’s outing. And it looked like a total success.

In the above photo Dr Singh is holding a decent looking sammie from Werribee Subway. I’m unsure whether the good doctor ended up eating this sub or not, but I do know that his probe had identified about 20 different chemicals. The baking compounds that it identified were 2-methylbutanal, 3-methylbutanal, and benzaldehyde. Dr Singh said that 2-methylbutanals and 3-methylbutanals come off foods as they're being heated, and create a “pleasant, roasted aroma.” The benzaldehyde, meanwhile, “gives you a nutty aroma, more like an almond.” Dr Singh said he was confident that all three of these chemicals are in Subway’s bread.

The probe had also detected acetic acid and butanoic acid. Acetic acid is a compound typically found in dressings, whilst the butanoic acid comes from Subway’s cheeses. “That is all we need for our nose to smell the product,” Dr Singh noted.

Dr Singh also found a bunch of other chemicals in the Subway smell sample: odour compounds that are typically found in cucumbers, milk fats, and a variety of food products. While he didn’t name these chemicals, we at least know they’re in there.

After receiving he CSIRO’s materials, my journey was finally over. I’d hypothesised that Subway’s fragrance comes from their bread and cookies. When I recreated these recipes, I thought that this hunch was correct—and I can now also name some of the compounds found in Subway's sandwiches. I’ve learned that the distinct scent is more complex than just a bunch of baked items. It is, in fact, a complex medley of 2-methylbutanals, 3-methylbutanals, and benzaldehydes, with some notes of acetic and butanoic acid.

So the next time you wander into a Subway, you’ll actually know what it is you’re sniffing. You’re welcome, Internet. You are absolutely welcome.

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