Our Approach to Roasting

SUNDAY, 2 MAY 2021

Roasting is one of those processes that is really, fundamentally simple, but that has heaps of complexity lying in the detail.

On the face of things a green coffee bean enters a hot drum (it could be a pan or an oven, basically any hot space) and tumbles around for typically 8-15 minutes depending on style and preference. Exactly like popcorn, the build-up of pressure from the moisture in the bean creates a pop (described as the first crack). Lighter roasts are stopped around this point and the coffee enters a cooling tray where the roasting is stopped and there you go, you have some freshly roasted coffee.

We roast all our coffee in Diedrich coffee roasters which we chose because of the ability to manipulate both the air and the drum. We roast our coffee across 3 different roasters, a 12kg, a 35, and a 70kg roaster.

As is the case through the journey from seed to cup, this particular process has a lot of nuances and the primary focus is on manipulating temperature over time. There are secondary focuses on aspects like conductive (drum heat) vs convective (air) etc. But at the heart of it, the roaster is figuring out how to manipulate the roast profile to create the most desirable results when the coffee is brewed.

This really means that although there is a development of what trends and markers there are to look for in the data, the real driver and check will always be how the batch tastes.

Our goal when we started roasting was to learn enough about roasting behaviour to create a tool kit of sorts whereby we can manipulate coffees to get the best out of them. We have developed starting points for different origins and cultivars and processes but ultimately these are open to change during the profiling of each coffee.

One of our key starting points is to roast hot with relatively fast drum speeds. By getting this energy in early we can get good development of body and sweetness as a base to the coffee. In terms of time we tend to roast relatively fast – typically around 9-11 minutes – to maintain citric acid and have bright and clean coffee.

Espresso and Filter Roasts

We develop two profiles for each of our coffees. Depending on the specific coffee, these can be close or quite different. Essentially we do this because of the dramatic difference in brewing concentration. Whereby most filter coffee is very dilute at 1-1.5% concentration and most espresso around 8-10% concentration. There are quite a few fascinating sensory studies showing that concentration dramatically changes a drinkers interpretation and sensitivity to certain flavour.

Our main goal in espresso roasts are to run a touch slower, breaking down some of the citric acid and developing a rounder profile balanced at high concentration, however the end temperature of the roast doesn’t differ much.

Saying this, we do develop all our profiles through an EK43 grinder and I find myself at home quite enjoying filter roasts brewed as espresso. Often when they go through a more traditional espresso grinder, these kinds of grinders get hot when the coffee is being ground fine and a brighter roast can help combat this.

This is really one of the many challenges of roasting, the grinding, the water, and the brewing will all define the feedback loop of what exactly sings in the cup.

Similarly, for capsules, we roast our shorts and longs with a similar approach. Considering that Nespresso machines brew a little cooler, we roast a little harder and faster to help with solubility when the brewing temps are a touch lower.

Like all areas of coffee, there is innovation happening in roasting and lots to explore. A few years back we collaborated on pre-treating green coffee whereby the coffee was rehydrated before roasting and this changed the roasting profile and the optimal results a lot. For us though, we are also adamant that exploring and experimenting is something we do separately. Only when it's tasting brilliant and has yielded an improvement do we then look to share it with our customers as an approach Colonna stands behind.

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