Grind size and how it affects your brew

March 02, 2021

So, you may have heard some baristas and coffee professionals talking about the importance of grinding your coffee fresh prior to the brewing process to avoid the loss of the precious volatile flavours and aroma compounds. The next point in such a conversation will usually be about grind size -  one of the most important aspects that influences your brew. 

 Brewing coffee with the Aeropress

In this blog post we are taking a closer look at the grind particle sizes and how this size affects the coffee brew. If you don’t have a grinder at home I highly recommend getting one. There is a wide range of hand and electric grinders available. The prices vary, and you can get some really cheap ones or treat that purchase as something that will be with you for life, so over the course of years it will be worth spending a bit more money on it. 

My choice is the Comandante C40 - click here to hear why we are enjoying working with it so much.

If you struggle with time in the morning and you are looking for an electric grinder then the Uniform Wilfa Grinder is a way to go. There are plenty of other bands too, I am sure you will find something that will catch your coffee eye and keep your wallet happy. 

Let’s now move to the important stuff.

 Coffee can be ground to a wide range of sizes

Ground coffee is much more soluble than beans, due to the bigger open surface that can be penetrated by water. Where possible always grind your coffee freshly before brewing. 

By grinding coffee, we expose its surface to a greater penetration by the water. The staling process occurs much faster once our beans are ground and coffee will start to lose its precious volatile flavour and aroma compounds. They start to degrade noticeably after about 20 minutes, so remember to grind your coffee as the last thing before you start your brewing process.  

If you are getting your coffee ground at your local coffee shop or a roastery then make sure you keep that coffee in an airtight container - it can be the original bag you got your coffee in if it has the reseal option or move it into a glass/metal container and keep it in a dark place, away from any extreme temperatures. 

I mean don’t keep your coffee in the fridge - ground coffee is super porous and it will happily absorb any foreign aromas from your fridge and trust me you don’t want to taste that in our morning cup. A cupboard away from the oven will be a good spot - coffee likes heat only when roasted and brewed, not when resting calming on the shelf - extreme high temperatures will also cause the loss of the volatile flavour & aroma compounds, so you won’t find them anymore in your brew. 

 The EK43 - king of coffee grinders?

You may have heard already about some sort of grind texture guidance, fine, medium fine, medium coarse, coarse. Well, when it comes to choosing or adjusting your grind you must first consider the brewing method as well as the brewing time.

The range of the home-brew devices is wide and so are the settings on your grinder. Depending on your brew method you may want to grind your coffee fine or coarse or find the perfect spot in between these points. 

Grind size and brewing time are strongly related one to another. If the grind is too fine and/or the contact time is too long, it will cause extraction of astringent and bitter flavours. 

If the grind is too coarse for the particular brew method or recipe then the time the water spends on extracting the flavour compounds might not have been long enough which will cause a quite sour or ‘under extracted’ taste.

When thinking about coffee extraction we must consider a lot of different chemical reactions that are happening within the brewing process as well the fact that each flavour compound extracts at a different point. We could simplify and organise the extraction of these flavour compounds in a general order: firstly we are extracting the acids, then sugars and finally, those bitter compounds which we want to largely avoid.

For the coffee brew to be pleasant and complex we would like to achieve a balance in between the acidity, sweetness and bitter qualities and avoid any astringent flavours. 

 coffee brewed using a drip method.

To do so, we must have a control of our brew recipe. 

Depending on the brewing device this recipe will vary, but there is so much space for experiments, you will definitely find the path which leads to your coffee tasting its best. 

Start with the coffee to water ratio, it would be great if you have a scale at home so you can control the amount of coffee and water. Any scale will do, it’s good to start somewhere. 

According to the SCA Golden Cup Standards the best brewing ratio to begin with is 55g/L. Saying 55g of dry ground coffee on 1L of water. If you would like to get a bit more precise info check our brew guides to see our recommendations. In these brew guides you will also find a tip on the grind size that works with the Comandante C40, thanks to the click technology. 

You’ll see that we tend to prefer at least 60g coffee per litre of water and sometimes more coffee for methods like the cafetière but strength is largely a personal preference so find what you like and brew to that. 

Don’t forget about the brewing time. 

For example, espresso machines will require fine grind settings as well as quite short time of extraction, we talk here between 20 to 30 sec. The highly pressurised water will pass through the finely ground coffee puck and penetrate its surface. 

On the other hand, when brewing your daily Cafetiere, I recommend medium coarse to coarse setting depending on the size of your device. Ground coffee is immersed with water, and the brew time mostly  varies from 2 to 4 minutes. We want to make sure we extract only the desired flavours from this coffee and that we extract them all equally. 

Another example is the gravity/drip method, like Chemex, in which water will be flowing through coffee at the same time extracting from it. Depending on the recipe you choose the brewing time might take up to 5 - 8 minutes. Super fine settings here would cause over-extraction, too coarse settings and coffee can be under-extracted. You are best starting off from a medium coarse size and adjusting it coarser or finer depending on your recipe and desired cup profile. 

 this is what we are trying to avoid

Right, so you nailed the recipe and got the grind size, but what if you are not happy with the end result? Does your coffee taste flat, sour and there is a lack of sweetness you’d expected from it? Or does it taste pretty bitter, ashy and heavy in your mouth? 

There is plenty that could affect the end cup, but grind size is most likely the one that gives us the best opportunity to fix the brew. 

Considering that we keep all the other variables the same, you can start to change the size of your grind. Go gently, and don’t be heavy on adjusting it coarser/finer as coffee grinders have feelings and most of them don’t need much to take you into the right place. 

If you are in the flat, sour group then change your grind a bit finer, if you are on the side of the bitter and astringent cup then go coarser. 

Observe what’s happening during the brewing process, I recommend to even record it, so you know where you are. Do small adjustments and see which one gets you to that sweet & complex cup of coffee. 

A few tips for adjusting your grind, especially when changing from one coffee to another: 

If your coffee has been grown high on the mountains you may want to take your grind on a slightly finer setting. Coffee beans grown at high altitude are usually much denser than those from lower elevation. The density of coffee affects the roast as well as extraction. Denser beans are harder to break, so the extraction of the flavours from it can become a bit more demanding. 

Roast degree is another important factor to consider. Longer exposure to heat in the roaster makes coffee beans more brittle, so if you have just changed from light to a medium/dark roast I recommend you go coarser on your settings. On the other hand, light roast is much denser, so you might have to set your grinder finer. 

Roast Date - please do check the date your coffee was roasted and if you can’t see any info on the bag, please ask the barista/roaster. Coffee is a food.. and best when consumed fresh! 

As soon as the roasted coffee has been rested, the ageing process will slowly take place. If stored in the correct conditions, coffee is at its best for the first 3 months from roasting date. 

Of course this will vary - to get a bit more info, read our blog post about it here. If your coffee is already a month or two old you may start to taste a difference in the cup. I recommend setting your grinder a little bit finer, and see if that brought something nice and new to that daily brew. 

I hope the info above made your life a little bit simpler ;) 

 Until next week, 

Magdalena.

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