Coffee Roasting Processes and Bean Choices

Coffee Roasting Processes and Bean Choices

This is one of the most involved topics due to the science and processes involved – just about all of which, you as the consumer do not need to know (although I’m finding that more and more people want to know regardless – thus the article). Firstly though, what you should know and be aware of is how a bean is roasted and to what level a bean is roasted – as both of these will affect the end taste and how it appeals to you – but only for that particular bean and in that particular style of roaster…. I’m already starting to get complicated….


The two most common types of roasters are a fluid bed roaster (or air popper roaster) and a drum or barrel roaster.

Very basically, a fluid bed roaster blasts the green beans with hot air (whose temperature generally has very limited control), rushing through them, lifting the beans mass and flopping it all around within the bean holding chamber until the desired level of roast is achieved. This type of roasting will traditionally give a brighter taste (cleaner, thinner, more crisp), whilst a drum roaster rotates the beans over and over (like a cement mixer) in a thermostatically controlled heated chamber and will generally give a more pronounced base palate, partly through a heavier body (thickness of the shot fluid that fills your mouth and coats your tongue) to the beans. There are other differences, but none really of significance to the average punter – and to be fair, your palate would need to be moderately developed to discern this difference easily.

Do you know which type of roaster is used by your supplier? Have you tried beans that have been developed in the alternate roaster that you’re used to? You should make an attempt to seek out the alternative – as their results may just be what you’ve been searching for… You can have the same bean roasted via the two different methods to nearly the exact same roast level and you will be able to tell the difference (in most cases quite clearly). As a reference, I use the drum style roaster.

Roast level

The level of the roast basically relates to the bean development stage when the roasting process was stopped. As a very general rule, the lighter brown the bean, the earlier the roast was stopped. A lighter to mid brown colour in the bean (somewhere between a darker honey yellow and a milk chocolate colour) will show a lot of the ‘origin’ characteristics of the bean. This will most commonly mean that the taste in the cup will be high in acid (tang/sour), high in natural non-caramelised sugars (which, when combined with the high acidity, still ends up more sour than sweet) with lower levels of chocolate and cocoa flavours and no burnt aftertaste. A mid to darker roast (the colour being somewhere between milk and dark chocolate) will result in a lower acid tang and much higher caramelised sugars. This will generally taste more closely to the cocoa and chocolate flavours that a lot of people seek – but still with great balance as the acid levels are more in sync with the chocolates. With this balance (dependant on the bean origin), the perception of taste will be sweeter and have much better ‘cut through’ in milk based drinks – i.e. tastes more like coffee than slightly flavoured milk (i.e. when you have a high acid level with minimal chocolates).. From here, the darker the bean, the sharper the taste – to the point of charcoal…. Take a look at the beans you have – determine their roast level and see if that translates to the flavours you anticipate in your cup. This can also help guide your purchases in the future.

Real Life Application

A better expanded tip on the above (with a story – as usual) – My brother and I went into a café along the Yarra boardwalk in Melbourne. It looked great – all decked out with palette racking, coffee sacks, a roaster and fancy machines and grinders. I looked up on the board so see several coffees listed with their cupping notes – bingo I thought, a café that should impress.

I ordered a ristretto of their single origin and my brother ordered a cap. At the time of ordering, I was specific about which bean I wanted whereas my brother wasn’t (as he didn’t have the knowledge and trusted the staff – fair enough). I gave this thought after ordering and told him I suspected that they were going to use the same bean in his cap that I had ordered for my ristretto. Normally, this may not have been a problem – except the bean I had ordered was fruity and acidic with minimal chocolates. This means it would be lively and superb in black, but insipid and uninteresting through milk. This thought was only half true. It was hopeless in the milk, but unfortunately it wasn’t much better in my ristretto.

The cupping notes did not reflect what was in the cup. I copied the cupping notes into my phone and did a Google search to find that the notes had been pulled straight off a green bean importers website and had not been created by the roaster after trying the roast (especially important when you’re roasting differently to get different results) – problem 1. Problem 2 was that the beans had not been roasted far enough – they were underdeveloped and tasted more like green beans than roasted beans – uninteresting, sour and plain – a shame. Problem 3 (and this may have been the biggest issue) – the barista gave no thought to which beans would suit which drink and used the same bean for both. This consideration is similar to a decision where you match a wine to a meal where a red suits a meaty, strong flavoured dish such as beef or a heavy bolognaise whereas a white will do better with creamy dishes or fish. For coffee, basically a darker, stronger or even sharper coffee is required to cut through the milk (as a general rule), to give great depth of flavour and balance whereas a fruitier, more acidic bean without such deep chocolates suits a black coffee where the flavours are not dulled or muted by the milk and can be enjoyed exactly as they were extracted.

Back to roasting – the problem with beans at either ends of these flavour spectrums (light roasts and dark roasts) is that they will only generally offer partial coverage of your palate. A lighter roast’s flavours will seemingly sit smack bang in the middle to top of your tongue. A darker roast will be more towards the sides and rear of your tongue. Don’t get me wrong, the flavours will move throughout your mouth – these are just the areas where there is the greatest perceived concentration. I say perceived because you don’t actually have a great deal of taste buds on the centre of your tongue. Another fact to point out for the pedantic – your palate is actually the roof of your mouth – but has become a socially adopted term to describe the location for one’s ability to detect flavours in food… I digress…. Again…

Beware of beans that are very dark with an oily sheen (mostly). You may prefer these –and that’s great – anyone can be misguided and make such a mistake (if you order from me and like them like this, i’ll point you in the direction of one of the many local fast food joints or servos that have adopted ‘barista’ made coffee – they’ll look after you). The caveat on this though are beans that have gone through the swiss water decaff process. These beans will roast up with a very dark colour and depending on their size, may release some oil from their surface – and still taste sublime. That aside, if you’re trying beans that fit this description and they tasted charred – this is not the bean’s fault. I’m not saying it is the roaster’s fault (I never want to be accused of pointing fingers – even though there are only the beans and one other factor involved in the roasting process) – I’m just saying it is not the bean’s fault…

As your beans are roasted, they develop flavours with many compounds being both destroyed and created. The final stages of a roast may or may not involve second crack (when the beans give off a sharper and quieter snick type sound). This is where the cell structure of the bean undergoes a more significant breakdown than they did before and during the first crack phase. During this phase, the oils (where a lot of flavour is contained within) begin to be released – consequently losing different flavours. I say different flavours because those that go are replaced with others – usually charcoal and smoke. But, if that’s what you like…

All jokes aside, some people do prefer a ‘french’ style roast. They like it dark and sharp with a big punch in your mouth type taste. You can actually achieve this with the beans I roast by mixing them with charcoal from your fireplace and battery acid from your car… I must stop going the gig before I manage to alienate the 3 people in Australia who enjoy such a cup. Sorry to you 3 – please move to France – Australia is quickly becoming a world leader in quality coffee. Unfortunately, there are very few places you’ll find here to make you such a catastrophe – I mean cup…

Seriously though – by modifying the brewing temperature in 1 degree movements either up or down, you can greatly alter the resulting shot taste from almost any bean – demonstrating a dramatic change in flavours – check out our article on brew temperature….

I think i’ll cover a bit more detail on roasting in my next article – as this one has sort of strayed off track – and I might as well continue this way…

Further Real Life Application to this Knowledge

When I go into a café, I look at the layout, the staff, their machine(s), their grinder(s) and their cleanliness. I consider whether they reflect what I consider to be a modern leader in coffee or just another joint cranking out cups without any care. I look at the brands and models of their machines and grinders. I listen to the staff and how they interact with customers and each other. I regard it as a bonus if the staff can demonstrate a higher than average coffee knowledge in these conversations with either staff or customers. I look at the barista’s routine and I look closely at the beans in the grinder hopper. I consider if they are grinding fresh for each cup, or each group of coffees or whether the grinds are just sitting in the dosing chamber for extended periods of time, quickly staling. I take the time to see whether the barista is correctly texturing milk and whether they are capable of simple latte art or not. Then when I ask for a ristretto, I like to see that they understand what I am after and create my cup accordingly (especially considering the simplicity of my request). I also enjoy when a barista or staff member can suggest which coffee will best suit a ristretto over another – I can easily choose myself, but will always enjoy the journey more when they are prepared to take the time to make such a choice for you – as they have the first hand knowledge with their beans.

At this point, I am prepared to order a coffee with interest.

I know, I know – it’s just like you’re looking into a mirror – I can hear what you’re saying now – “That is exactly what I do when I go into a café” and “Everyone I know does that”….

Or… perhaps not….. I doubt it though – I’m sure everyone is exactly like me 😉

I digressed again… The point I was trying to make was – when you go into a café, open your eyes. You are the customer. Are they clean? Look at the beans in the hopper – does their colour suit your taste (very rough measure), is there a ton of grinds sitting in the dosing chamber on the front of the grinder? Are they turning over a heap of coffees or has the machine been left idle for hours? (This is not such an issue if the machine’s brewing groups are pid controlled – but can become a problem if the machine is heat exchanger – check our article on coffee machines for an explanation). Do they care about the coffee they are making? Are they just working to earn a dollar or do they exist within the café culture to improve it? These questions and a lot more, when asked will more likely lead you to a favourite coffee hot spot for years to come.

Why would you ever order “just a cup” when you could walk another 100 metres to find a café that is doing magnificence in a cup each and every time? Don’t settle – but also don’t be too quick to judge. Just because a café doesn’t have all the fancy trimmings, doesn’t mean they can’t put out a top shelf cup – and the opposite is also true. Try, but don’t settle. The next best thing might be just around the corner.

I think I’ve gone off subject again…

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