Coffee bean density is important data for roasters, green coffee buyers as well as producers. It’s often seen as a quality score, but to really understand coffee density you need to understand what makes coffee “thick” or less “porous”, how they are graded, as well as how density affects roasting and the final flavor.
This article will try to shed some light on why coffee bean density is such an important metric, but first, you should go over a few caveats.
While most international literature uses ” less dense “, ” more dense ” to describe the density of a coffee bean. Then in some cases you will come across terms like: Soft Beans (SB), Hard Bean (HB), Strictly Hard Bean (SHB) – These physical descriptions look rather complicated for coffee, but we’ll make them very clear shortly; And while we wait for the coffee community to unify the names, this article will use descriptions like “thick”, “foggy”, “hard”, “soft”, although that may not be entirely accurate, but it’s simple and relevant – so feel free to ignore it if this doesn’t fit your concept.
What is particle density?
Density is how dense a substance is. You calculate it by dividing the mass of an object by its volume. In the case of coffee, density is the ratio of the weight of the coffee bean to its volume, in units (g/ml) or (g/cm 3 ). And since laboratory densitometers are expensive, before you do the particle density calculations yourself, check out the following figure.
Usually, just by looking at coffee beans, you can tell which ones are harder and stronger. If the crack in the middle of the grain is straight and slightly open, the grain may be more porous (less dense). Conversely, if the crack is tortuous and closed, the grain may be denser. For coffee professionals around the world, bean density is recognized as an important metric for grading and grading green coffee by quality. Harder, denser nuts – as usual, will be prized and, as a result, farmers often receive a premium.
A coffee bean is basically like a beehive. It is a hollow cellulose structure (similar to wood). The job of this structure is to hold nutrients for the embryo. However, sometimes the granules are only partially filled – and so it’s more “porous” with a weaker flavor. Whereas “thick” beans contain more flavor precursors, so this leads to more flavor after roasting.
For green coffee beans, high density means that the beans have a larger number of cells and a more compact cell structure than coffees with lower density. The way that a particle absorbs energy, experiences stress, cracks, and grows will be different than a particle with a lower density.
What makes coffee thicker or more porous?
Roasters are often quite concerned with whether coffees are grown at high altitudes – an indication that beans tend to be denser. Cooler weather in the high mountains, especially at night, slows down the ripening of coffee cherries. Longer time on the plant leads to more cells multiplying inside the seed, resulting in higher density
However, altitude does not by itself determine density or grain quality. We need to discuss a few more issues shortly.
Expansion beyond altitude & latitude
What we are certain of is that the respiration of the coffee plant slows down the higher it goes, which means that the coffee retains more of its sugars and nutrients. That process directly affects the final flavor in the cup. So theoretically the taller the coffee tree, the better, right? Both are correct AND incorrect.
It is true that the more elevated, more delicious flavor, but when too high, the tree must deal with the problem of frost (Since every increase of 100m is the temperature will decrease 0.6 ° C – Geography class 6). So the standard altitude for coffee farming is usually no more than 2,200m – But this is around the equator like Ethiopia, Kenya, etc. (see more about the effect of altitude on coffee trees).
Some other factors affect particle density
Coffee farmers can rely on altitude to strengthen seed density by inhibiting plant respiration. But that only allows small areas of arable land. In addition, there are a number of factors that will have more or less impact on grain density (actually directly affecting the temperature rise/fall in the coffee-growing area) as follows:
- Shade for coffee plants – Various types of shade plants can provide shade to help cool the plant and increase seed density after-ripening (see also Shade grow coffee ).
- Plant Density – This depends on whether you want the coffee tree to shade itself or not. Standing close together keeps the plants cooler and less stressed from the sun. So, the closer the plants are to each other, the greater the seed density.
- Slope – If possible, plant on the north side of a mountain, so that the sun does not hit the tree directly. This can lead to cooler temperatures, slower cellular respiration, and greater particle density.
But altitude and temperature are not the only factors that play a role in determining the density of coffee beans (although very important). There are many other factors that contribute to particle density. It is the diversity of nutrients in the soil, the source of the cultivated seeds, the ripeness of the fruit, the processing and preservation techniques, etc. both play a decisive role in the density of coffee beans.
On the same tree, the seed density is also completely different between the fruits. The cherries at the end of a tree are usually porous and less dense than those near the trunk because nutrients are distributed centrally in the middle of the tree.
Particle Density Classification
Unfortunately, the coffee industry has no unit of measure for bean density. Some countries describe coffee grown above a certain height as “ Hard Bean ” or “ Strictly Hard Bean ”, but this goes back to the original problem: Altitude does not completely determine density & quality. number of seeds.
And in this popular but informal way, coffee experts often rank the hardness of the beans into a number of different grades. However, the specific terms & standards used vary from country to country:
- The terms Soft Bean (SB) and Strictly Soft Bean (SSB) generally refer to coffees grown at altitudes below 1,200m. At low altitudes, higher (and less stable) temperatures and high oxygen levels make the coffee plant work harder, having to consume stored sugars for energy. As a result, the seeds are less dense and tend to be less sweet and sour.
- Next, you have Hard Bean (HB) or High Grown (HG), which is a coffee grown from 1,200 to 1,370m. At these altitudes, the cold atmosphere and less oxygen slow fruit development, giving it the opportunity to store more sugar, thickening with a more complex flavor profile.
- Above 1,370m, grading starts to get a bit more difficult, as the actual elevation depends on the region and origin of the coffee tree. Finally, coffee grown at these altitudes can be called Strictly Hard Bean (SHB) or Strictly High Grown (SHG).
The meaning of particle density
First, the particle density doesn’t matter too much – if you care about it the right way. For green coffee beans, a higher density tells us that the beans are firmer. The way that coffee beans absorb energy, withstand pressure, crack and grow will be different than the softer, more porous beans.
Second, for coffee roasting , we are mostly concerned with relative density. In other words, we only need to understand the differences that occur in roasting and flavor quality between beans of different densities.
Example: You go to a basketball game to recruit potential players, you just pick the tallest one or two – you don’t care what their actual height is. For coffee, we can really judge density by visual observation (as mentioned above) instead of working into mass density calculations – if you are scientifically minded .
Roasting coffee with different density
First of all, there is no specific recipe for roasting hard or spongy beans. Seriously, there are too many variables to consider. However, there are a few guidelines that you can take into account when combining particle density with a number of other factors:
First of all, solid granules have a tighter, more complex cellular structure. This structure creates more potential for sugars and acids to develop during roasting. If you roast seeds of different sizes or densities, they will develop differently through the roasting process. For real consistency, it’s important to separate them and roast them individually.
Second, dense beans will conduct heat more efficiently and will usually roast a little faster. Sponge beans may take longer to roast and heat transfer takes place inside the beans more slowly (porous beans contain more air), high roasting temperatures can lead to scorching and uneven growth. (see more about the roasting process ).
Another note from Scott Rao, is that wet-processed coffees tend to be denser and require more thorough roasting. Meanwhile, dry processed coffee burns more easily during roasting. This is because processed coffees are naturally higher in sugar , causing them to burn quickly and easily. Therefore, it is recommended to use a lower intake temperature and air setting when roasting those beans.
Research from your own coffee beans
Understanding density only becomes more interesting as you learn more about your own beans. The denser seeds should allow for a better growth, and you can roast them at high heat. But don’t forget to record the Roast Profile if you don’t understand more about the coffee in your roaster, it makes no sense to wait for a specific profile to be available on the internet.
Finally, it can be seen that grain density is a complex subject and is only one of the indicators used to assess coffee quality & grading . But it’s an important parameter for roasters to monitor. By understanding why coffee beans become firmer or softer, and what this means for the roasting process, coffee roasters will be able to tailor their roast profiles to suit and standards. get better with the batches of coffee they buy.