Roasting coffee at home is a fun process that enables you to experiment with roast times to see how it influences flavour. In the UK we are seeing more and more artisan coffee roasting companies entering the market. Many of these companies sell their product direct to customers on a subscription basis, promising to deliver coffee freshly roasted through the post. Coming soon will be my review of a few of these suppliers, however this post is all about roasting coffee yourself at home.
I first got the idea to roast my own coffee from Tim Hayward’s inspirational book, Food DIY. Tim’s a brilliant and witty food writer who has influenced many of my food experiments. He recommends using a paint stripper heat gun and wok, however after some research I decided to follow the popcorn popper method. I made this decision having read the useful website Sweet Maria’s Home Coffee Roasting. Interestingly, a search on Amazon UK for “Coffee Roaster” returns many results with the number two product being a popcorn maker! (Number one being a device specifically designed for roasting coffee, with an eye-watering price). So I ordered the popcorn maker, some green coffee beans, and eagerly awaited their delivery.
Having seen some reviews of the popcorn maker, it seemed the plastic lid (designed to deflect the popped corn into a bowl) begins to melt with the long continuous use needed for roasting coffee. A number of people have come up with various “hacks” to avoid this. The most elegant I saw involved making a metal mesh chimney to replace the lid, so I thought I’d copy it. When the popcorn maker arrived, I made a quick trip to Wickes builders’ merchants and bought a large sheet of 6 mm wire square mesh. I cut and rolled the mesh into a “tube” 20 cm long that snugly fitted into the top of the maker. This would allow the lighter chaff to be blown out of the roasting chamber while preventing the heavier beans from hopping out.
The green coffee beans I chose were from Fazenda Da Lagoa, Brazil which were advertised as being ideal for home roasting. I filled the popcorn maker roasting bowl with enough beans to cover the hot air vents in the side walls of the roasting chamber. This turned out to be 60 grams.
I inserted my mesh chimney, started a timer and switched on the machine.
Soon after the beginning of the roast, the papery skins of the beans started to float up out of the chimney. After 4 minutes, the first crack began. I could hear the beans pop as they expanded in the heat.
As the coffee continued to roast, the aroma emitted started to build. The smell is bread like, or perhaps similar to burning toast! If you’ve ever travelled to London Waterloo by train, the track passes Costa coffee’s roastery in Lambeth. You can often get the strong burnt toast smell of the coffee being roasted in the mornings. Commuters must worry about experiencing phantom smells in the mornings. (Phantosmia– often associated with strokes, brain tumours and other serious conditions!)
After 8 minutes I could detect further popping noises – the signature of a second crack as the oils within the coffee bean are driven to the surface. Soon after I switched off the popcorn maker, removed the chimney and poured the beans into a metal colander to cool. The metal conducts the heat away from the beans, and the holes enable cool air to circulate. Spreading them out on a large flat baking tray also works.
Once cooled, I weighed the beans again to see how much moisture (and chaff) had been lost. After roasting the beans weighed 50 grams, having lost 10 grams. In the following picture on the left is 60 grams of green coffee, and the equivalent quantity of beans after roasting. As you can see, the beans have expanded significantly and achieved a very even roast.
I transferred the beans to an airtight container, and let them rest for 24 hours. Having ground the beans using a burr grinder, I made my first cup of coffee using an Aeropress. The home roasted coffee bubbled and foamed significantly when hot water was added, signifying that the coffee still had allot of carbon dioxide within it. I have to admit that as it turns out I had over-roasted the coffee. The flavour was a fairly generic, French or Italian dark roast (low acidity, high bitterness) lacking interesting character. However, I was pleasantly surprised and impressed with how good the coffee tasted on first attempt. I would say that it was equivalent to, if not slightly better in quality than, the big brand coffee beans that are available in the supermarkets.
My second cup (48 hours after roasting) was an improvement and a third the day after was even better, which suggests that coffee can develop in flavour during the resting stage. On this basis, I plan my next roast to be a lot shorter, perhaps only continuing on 2 minutes after the first crack, and certainly avoiding the second crack. I will also allow the beans to rest at least 3 days before use.
To conclude, I would say that roasting your own coffee enables you to adjust and experiment with the roast to see its influence on flavour. It’s possible to increase the roast temperature (and overall reduce the roast time) by roasting more beans in a single batch, and partially covering the air intake of the popcorn maker. When added to all the other variables of coffee making such as quantity, grind size, and brew time you gain appreciation of the complexity of the coffee making process and the need for precision. Coffee and coffee-making have long been a hobby for me (having tried out numerous gadgets, coffee suppliers and methods) and home roasting was the next logical step. I will continue to experiment with the batch of beans I currently have (another 14 or more roasts!), until I think I’ve found the optimum conditions. After that I look forward to roasting a different green coffee, which no doubt will need further experimentation to find the ideal roast.
Good luck with your own roasting ventures! Leave a comment below to let us know how you get on or if you have any tips of your own.
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