A Deep Dive into Coffee Roasting with Pig Iron

Turning raw green coffee that tastes like dirt and green vegetables to the sweet and delicious beans we use to make our daily cup takes a lot of skill and intention. We chatted with Jason Tan, Head Roaster at Pig Iron who developed his skills when he was trained by Scott Rao, the man wrote the book on coffee roasting – which isn’t a saying; Rao actually wrote one of the more prominent coffee roasting books, “The Coffee Roasters Companion”.

“I idolize some coffee roasters and I just want our coffees to have that same vibrancy and just the same impact that those roasters had on me. I want that same impact on some other people that try our coffees,” shared Tan on his motivation for coffee roasting.

Here’s his walk through on the process of roasting.

“We’re using heat to manipulate the way coffee tastes.”

Sounds easy, right? Not so much. In fact to get coffee tasting delicious it gets exceptionally complicated. First off in the process is the charge temperature.

“It’s the same as when you bake something in the oven, you preheat the roaster, you let it heat up to a certain temperature, and for particular coffees the temperature that you pre-heat the roaster are different,” shared Tan.

The charge temperature, which will depend on the batch size – so how much coffee you’re planning on roasting. Also, what type of coffee you’re using –is it a really dense varietal? What’s the water content? How big are the beans?

“When it comes time to actually dump the coffee beans into the roaster, you have to charge the gas up so that when you dump the coffee in, the temperature doesn’t just plummet and just stall, you need to turn the gas up so that the coffee slowly rises up to temperature, the coffee then turns yellow and from yellow to brown, which is indicating the Maillard reaction.”

The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, which forms aroma and flavor compounds. Hundreds of flavor compounds are formed from this reaction, including the coffee aroma flavor compound, 2-furfurylthiol (2 fur-fur-ill-thy-all). Don’t you love the great scent of some 2-furfurylthiol in the morning?

“As soon as the coffee starts browning, you hit something called first crack, and that’s when coffee releases all the moisture inside the bean, and that’s kind of when the development of coffee flavour starts, you get your apple, strawberry flavours develop as you roast, there’s an optimal period where those flavours will peak, and anything after that, the flavours start to get lost, and you get more burnt and charcoal flavours in the coffee. So when we hit that point in the roast that we’re looking for, we drop the coffee in the cooling tray and that’s when the roasting stops,” explained Tan.

"...there’s an optimal period where those flavours will peak, and anything after that, the flavours start to get lost, and you get more burnt and charcoal flavours in the coffee."

The reason for the name “First Crack”, is because the coffee actually does make a cracking sound at this point – the water inside the bean vaporizes, causing the bean to expand and crack.  It’ll sound like popcorn popping.

But all that steam that is being released causes the temperature inside the roaster to drop significantly, so the roaster needs to adjust for that to get the temperature they want and to bring out the flavours to expose –this part is super important in determining the balance of acidity and bitterness.

“All the stuff that you do before first crack impacts how first crack happens, you can’t just say ‘I’ll crank up the heat after 1^st crack to offset the steam that’s giving off’, that’s not the way it works. You have to plan your gas changes before 1^st crack happens to guide the roast in the right direction. It’s very complicated, that single step took us… it took us almost 8 months to figure out what we were doing wrong.”

And for a roaster, all they’re doing is manipulating heat over time, but incredibly meticulously. 8 Months to get a specific step correctly! And that’s not even talking about some additional factors that might influence roasting.

“Especially when in Toronto, where there’s 4 different seasons, the facility that we roast in isn’t completely isolated so it is a little difficult with the changing seasons, to see how the coffee is going.”

“When I was out west for the Seattle coffee show, I was talking to a few roasters from Portland, because they have a pretty temperate climate, and it’s the same all year round, so there’s not much variance in how they roast. In Toronto the weather will vary significantly from what it’s like in the summertime, especially in those transitional times like fall and spring, you never know what days are going to be like; it can be really hot one day and the next week it’s really cold, so that’s hard to manipulate.”

And then, you still have the stylistic choices to make with roasting. What are you trying to prioritize in the roast?

“At least from Pig Iron's perspective, we want to create a coffee that’s super sweet and super balanced. We still want you to taste the notes from origin, but however, that’s kind of secondary to the balance and sweetness that we want out of our coffees. That’s not to say we want to destroy everything that you should taste in origin, but we think that it’s a lot more approachable.”

“We tried roasting light and it was okay, but it was hard to find consistency. So with roasting, it’s more about caramelizing the sugars that are in the green bean into something sweet that you can taste in the coffee.”

“It’s really just chasing the goal of finding a really nice coffee, roasting it our way, and finding a way to perfect it then just having the luxury of tasting that coffee over and over and again.”