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Chillout TGIFridays: Stay home activity: Hand roast your own coffee

by Peter Chong on April 24, 2020

Learn a craft while staying at home and keep safe during these troublesome times of COVID-19. This episode – how to hand roast your own coffee.

This set of photographs were taken from an article written and published by me in collaboration with my coffee mentor – Prof. Thanet Makjamroen, and taken in his residence in sub-urban Bangkok in 2009. I learnt roasting and pulling espresso from Prof Thanet in about 2002, and have been trying to perfect the art ever since.

My espresso setup – on the left a commercial grade burr grinder – the Mazzer Mini, and on the right, the Elektra Micro Casa a Leva, a traditional lever machine.
Photo from 2014, this set-up was purchased circa 2002.

The initial learning curve is very steep, but in my mind, totally worth the trouble. Progress in the last decade, this is steep curve is somewhat leveled off with use of computerised roasting machines which can be programmed with roast profiles. One can choose a pre-made profile from the manufacturer and modify from there.

However, I prefer everything to be done by hand, so the method I am sharing will be a manual process where the level of roast is determined by experience, purely by feel – visually, aurally and by sense of smell. Other methods of roasting using the same manual process may include wok/frying pan roasting over a stove top, using a pop-corn popper, or one of the many electrically driven roasters in the market .

The green coffee beans

We begin with fresh green beans. Many online and brick and mortar shops offer unroasted green beans. The green coffee beans have a greenish, grassy smell, quite unlike roasted coffee that we are used to. The beans are dry, and nutty to the touch. Good quality beans are essential. In the photographs, the beans used are very high quality Arabica beans from the Doi Tung estate in Chiang Rai, Thailand.

In this article, I will discuss one method to roast single origin beans, and will result in a single origin espresso. For most of my own drinking, I only use Arabica beans, which tend to have a more delicate aroma and palate – sweeter, softer taste, with tones of sugar, fruit, and berries. Robusta and Liberica, however, will have a stronger, harsher taste, with a grain-like overtone and nutty aftertaste. Beans can also be blended and blending can be pre or post roast, and espresso can be blends of as many as 3 or 4 beans. In fact, most Italian espresso is such a blend, and often comprise of a small amount of Robusta beans. However, it will be beyond the level of complexity of this article and we will not be exploring it.

Green coffee beans. This is from the Doi Tung Project in Thailand.

Also, part of the fun of coffee is to try out beans from all over the world. From South America, Africa, India, Indonesia, Vietnam all produce good quality beans. The terroir, or the land where the coffee is grown, and the weather is incorporated in the flavour profile, much like it does to grapes which show up in the wines made.

A further level is to age the beans before roasting. I am currently drinking a batch which I bought in 2008 and have been aging for 12 years. Not intentionally, as I forgot about these beans sitting in a corner of my pantry, and recently re-discovered that I had them. The taste, and aroma from the espresso made from these beans have an intensity which is quite amazing, with a very long finish.

How to roast coffee – hand turned stove top roaster

I use a home roaster is made of stainless steel, designed by Prof. Thanet from books and literature of traditional designs. The simple roaster comprises of a cylinder, attached to a handle. The insides contains fins, which agitate the beans as the cylinder is rotated. In the picture below, the hatch is opened to fill the cylinder with beans. It sits on a very craftily designed set of legs, and goes over a gas stove. Very well built.

The green beans inside the roaster.

I begin by filling the roaster up to about a third of the volume. In this roaster, this should be no more than 300 grams. This is because the roasted beans expand during the roast, and you want to have enough space to keep rolling the beans inside the roaster.

The roasting process takes about of 12 minutes, during which the beans grow some 50% in size, and undergoes what industry insiders call two cracks. The first cracking, referring to the sound the beans make as they split open under the heat…not unlike the cracking of corn to make pop-corn. At this point, chaff begins to be blown out of the ventilation openings. As we continued to the second crack, smoke pours out of the ventilation openings in the roaster. And we turned out the heat, and pour the beans onto a tray to cool.

Put the roaster on top of the stove. Use medium heat. What is medium? Use the heat level that will finish the roast within the 12-14 minutes range. For example, if it takes too long, turn up the heat the next roast. A larger amount of coffee beans also prolong the roast time. So if you use a lot of beans you have to compensate the heat (higher) so that the roast is still done in 12-14 minutes.

The roaster goes over a stovetop burner.

Turn the handle to make one revolution every 2 seconds or so, to ensure even roasting. Do not take the roaster away from the fire before the roast is done, otherwise the roasted coffee will be bitter and have off flavor.

Wait for the first crack that should come at around 9-10 minutes. This is the beans exploding due to the carbon dioxide being released from within. The chaff will start coming out from the openings of the roaster , first a light hue of the silver membrane covering the beans and eventually will change from a pale orange to tan to dark brown when the roast is almost done. After a while, the first crack will settle down and the roaster will become quiet. If you stop the roast at end of first crack, the beans will have an orange/light brown colour. And an espresso brewed with these beans will be acidic and sour – a taste profile known as bright. The terrior of the beans will show at this stage, so it is useful for cupping and tasting. But this level of roast will not result in delicious espresso.

Continuing with the roast, the second crack will occur soon after the end of the first crack. This is usually louder and more explosive, and can be so violent that bits of the beans can be blown apart. You have to estimate the roast from the intensity of the smoke coming out of the roaster, and how it smells. For a full dark roast, suitable for most espresso drinks, this is when the smoke coming out is like a jet stream of a kettle of boiling water, with a smoky aroma. The color of the smoke will change from white to white with a yellow tint.

Once the desired level of roast is achieved, open the hatch, and dump the beans.

You can also use a fork to knock the door of the roaster to see the color. But do it quickly. Look for the color just a bit lighter than what you want. After you stop roasting the color will continue to change and become a bit darker.

Use a fork to move the beans around to aid cooling.

Once the desired level of roast is achieved, dump the beans into a collander or a cool baking tray to stop the roasting. To aid the speed of cooling, use a fan to blow directly on the beans. This will also blow away some of the chaff which remain with the roast.

These beans are roasted to a very dark roast – evidenced by the film of oil on the skin. For my own roasts, I stop the roast before this level.

When cooled to room temperature, put the beans in a container, preferably an air tight one. And leave the fresh roast for about 3 days before roasting. This resting stage is very important, as the fresh roast continue to release carbon dioxide and other gasses. The aroma will change from the smoky, grassy smell, to the complex, multi-layered fragrance of coffee. The roast is best from about 3 days to about 15 days, before it goes stale.

My latest roast, done two days ago. Bolivian Bird Friendly Superior AA, Nov 08, done to a full dark roast, but not as dark as the ones roasted by Thanet. Note that the beans do not have an oi film on the surface.

After roasting, rinse the roaster with tap water. You do not have to use soap. Just be careful that the roaster is extremely hot.

Next episode on May 8: How to brew an espresso using a lever machine.

Update 27 April, 2020: Delayed! Espresso machine and grinder being upgraded! We will be back with the how to brew espresso article when the upgrade is completed.

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