How We Roast Coffee

Martin Carwardine with a coffee roasting machineAt the heart of our coffee production is a magnificent 1968 Probat machine, nicknamed ‘Bertha’.

Six reasons why the coffee we roast is great:

Bertha’s Seasoned Drum : Being over 40 years old the chamber is wonderfully seasoned and produces glorious coffee under my watchful eye. A new roaster takes time to attain this, similar to the rules surrounding a wok but taking much longer.

Water quench: This machine is completely different to many modern machines in that it doesn’t water quench the beans. This practice really isn’t good for the coffee as the hot beans will become steamed, dulling and altering the flavour. I have seen and used such a machine and have directly compared the two. Apart from the differences in character, the coffee simply smells so different when it is ground. Yes I am sure it helps the roaster's margin as it will reduce weight loss but it does nothing for the coffee. I will never water quench, water should only be used when you want to brew the coffee.

Aroma valve: One feature this machine has is what is referred to as an ‘aroma valve’. Put simply when the coffee is almost ready I turn the gas off and turn off the valve closing the exhaust ventilation. This means the coffee continues to roast in its own heat and smoke, capturing some of the flavours that may have literally gone up the chimney!

Direct flame : There is a modern trend towards using indirect heat sources. This Probat doesn’t, enjoying direct flame which results in a full and developed roast. Many times I have cracked open the beans from other machines finding the coffee not evenly roasted and brown to the core. While that may be fine for your roast beef this is not good for great coffee and under-roasted coffee will taste undesirably grassy and thin.

Weight: One often hears of the term ‘built like a tank’ but this really is. Weighing in at over two tons this machine is from an era when industrial plant was made with heavy gauge metal and cast iron frames. These days, with the price of metal, corners are cut and economies are made. Pressed steel is used as the bean counters act to trim and lighten the design. On the face of it that is fine saving natural resources, however and critically the older heavier machine will have greater thermal retention and stability. All that metal soaks up and retains the temperature, so when a great load of raw coffee is dropped into the chamber the heat will transfer more stably into the beans, giving a better roast.

Roasting by origin: I roast every variety of coffee independently. Each coffee roasts differently, yes some very similarly but some are certainly not. By doing this one can tune the coffee to extract the best from each variety. This means a lot of hard work afterwards if one needs to create a blend as one then has to weigh off the beans to mix as an extra process which is why most coffee roasters don’t! The norm is to blend the raw coffee first, thus avoiding the extra work, however it’s not the same. A basic analogy I use is that you wouldn’t cook your peas and carrots together, it’s the same idea.