Types of Coffee Grinds
We review the types of coffee grinds for different coffee drinks. It is definitely worth investing in a good coffee grinder if you don’t have one already, it can make all the difference to the taste of your favourite coffee drink.
If you just started indulging in the art of making a delicious fancy cup of coffee at home, one of the most important elements to get right, is the correct grind size. Grind size can turn your coffee from decadent into disaster if you are not careful.
Why size does matter?
There are three factors to keep in mind which will make a big difference in a good cup of coffee or a bad one: contact time, extraction rate and the flow rate.
The extraction rate of the coffee grounds will increase with a larger surface area. To increase the surface area, you need to make the coffee grind finer. If a higher extraction rate is required, less contact time is needed. A finer grind can decrease the rate of water flowing through the coffee grounds, this will increase the contact time.
If you use a brew method that requires a short contact time, the coffee grind should be finer. For an immersion brewing method, which infuses the coffee grounds in water for a few minutes, the contact time is much higher and it requires a coarser grind than the other brew methods.
The science of grind size vs extraction time
To explain it in very basic terms, imagine dunking a whole coffee bean into hot water. You don’t have to be science expert to figure out that it will take quite a while to extract all the caffeine from the bean.
Now, imagine cutting the bean into half before dunking it into the hot water. Yes, you guessed right, this will speed up the process. This is the basic concept for determining extraction time. The finer the grind, cutting the bean into tiny pieces, the shorter the contact time will be.
Creating smaller coffee particles increases the surface area. Smaller particles also shorten the distance from the center of each little particle. This increases the extraction possibilities of oils, solubles and other flavoring elements found in the beans.
What happens when I mess up the contact time?
If the contact time is too long or your grind is too fine, this will result in an over-extracted brew that will be quite bitter. On the other hand, if the grind is too coarse and the contact time too short, your coffee will be weak. Finding the proper balance between the two will help to produce the perfect cup of coffee.
A few other other factors to keep in mind that will affect the grind, is the type of filters you use, the pressure of the brewing method and the water temperature.
Something else that influences the process, is the moisture content of the beans. Usually roasted beans either went through dry processing or wet processing. Water processed beans tend to distort unevenly when you grind them and this produces uneven grind particles.
Lighter roasts are usually more pliable than darker roasts. The moisture has been extracted more in dark roasts, making the beans more brittle. Darker roasts produce more fine particles than the lighter roasts.
Furthermore, the origin of the beans will also affects how the grinding is affected. Natural coffees definitely grind differently than wet processed coffees. New crop coffees will usually produce fewer fine particles than the past-crop coffees. This is due to the differences in the cell structures. Altitude will also affect the grinding, beans that are grown at a higher altitude tend to be more dense than those grown at a lower altitude.
The US Department of Commerce created a testing procedure in the 1940’s for measuring particle distribution. The RoTap consists of four wire screens, stacked on top of each other. The machine is then attached to a vibrating machine, shaking the particles inside the sieve, causing them to fall through the various screens of different sizes, to create a particle distribution.
To set an estimate from the sifted particles, 3.5 ounces (100g) of roasted ground coffee is used. It is placed on the top sieve and the machine shakes for five minutes, distributing it through the various sift sizes below. Afterwards, the sieves are removed. The coffee remaining in each sieve is weighed to determine the particle distribution. From this method a standard particle distribution curve has been created for classification.
Which grind size goes best with which type of coffee?
There are so many different kinds of brewing methods, you need to experiment with the grind size to use to make sure you create the best possible cup of coffee. Let’s look at a few of the most popular ones.
A Turkish coffee needs an extra fine grind size, close to the texture of powdered sugar.
The espresso is used for cappuccinos or lattes. The brewing method uses pressure to force the water through compacted coffee grounds. So the contact time is very short and it requires an extra fine grind size.
The AeroPress is a new popular single-cup manual coffee maker trend, similar to the French press. The recommended grind size is somewhere between medium and fine, depending on your preferred steep time, from a weak cup to extra strong.
Siphon brewers also use pressure to force water into a special compartment that holds the coffee grounds. Once the soaking process is finished, the heat is removed and this creates a vacuum in the lower chamber that pulls the water through a filter. This method requires a medium to fine grind size.
The pour-over brewers come in various different shapes and sizes. The different types require different grind sizes to control the flow rate of water through the grounds. But you will be on the safe side if you stick to a medium to medium-fine grind size.
A stovetop espresso maker or Mokka pot uses steam pressure to force the water upwards through a filter basket full of coffee grounds. The contact time is short, but the pressure is a bit higher than your average manual coffee brewer.
This method will produce the best cup of coffee with a medium coffee grind size.
With a single-cup coffee maker or standard drip brew machine, the contact time is fairly low. This means that a medium to medium-fine grind size is perfect.
Top Tip: How do I know when the coffee grinds are at the medium level? It has a similar particle texture to table salt.
The drip coffee method is usually used in a cafe or coffee shop, producing traditional standard filter coffee. The contact time is regulated by a small hole in the bottom of the brewing basket. The recommended grind size will vary between medium-coarse to medium, depending on the type of machine.
The French press uses an immersion technique. The water is added to the coffee grounds in a glass container and allowed to brew for a few minutes, depending on the strength you prefer, before you push down the filter to drain the grounds.
The method works best with a coarse grind.
The Cold Brew method, is done at room temperature or below and it takes between twelve to seventy two hours. This is now like the example of dunking a whole coffee bean into water, patiently waiting for the caffeine to seep out of the bean into the water.
Because of the low temperature, the extraction rate is very low, regardless of the grind size used. Coarse or extra coarse coffee grounds are easier to filter. A finer grind size will also work, with a slightly shorter steeping time, but the final brew could appear a bit cloudy.
When do I grind finer and when is coarser better?
A good gauge to keep in mind for grinding coarser or finer is the following: If your cup of coffee is too weak, try to use a finer grind size. If the coffee is too strong or it tastes bitter, a coarser grind size should solve the problem.
These are all recommendations to make the most of each brewing method. But your personal preference will influence the grinding process. Remember, you might not make the perfect cup the first time you try a new brewing method and you have to adjust the grind level depending on the type of method used. Keep trying, as the saying goes, practice makes perfect.
Next time we’ll look at a few nifty little gadgets to make your home brewing even more fun!