Ground Coffee: What’s Wrong with It?

Every day we use ground coffee to make our beloved cup of Java. Yet have you ever stopped and wondered why we use ground coffee as opposed to just whole beans? Or, why does the size of the grind matter? Or, why do some people look at you with utter disbelief when you tell them that you use ground coffee?

Well, I by nature do a lot of wondering. So, stick around and find out the answers to these questions.

Why we Grind Coffee?

The basic goal of making coffee is to get what’s sealed inside the bean (namely, the delicious flavor components and oils) out of the bean. The original method involved boiling the whole roasted beans in hot water while agitating them. With some patience and lots of time, you’d eventually end up with a bitter, high-caffeine, coffee solution.

Luckily for us, our coffee forefathers eventually came up with a more efficient method to extract the goodies from the coffee! By grinding the coffee beans you help the water to extract efficiently the solubles that are responsible for the taste and aroma of coffee.

Let me explain the logic behind this.

The Efficient Extraction of Solubles

If you take a whole bean and cut it in half you’ll increase the total surface area of the bean. As a result, the extraction efficiency is greatly increased. Why? Because there’s more surface area for the hot water to act upon and from which to extract the flavor components.

Now take these two halves and cut them into halves again. Guess what, you’ve just further increased the overall surface area and thereby helped along the extraction efficiency even more. Eventually, you’ll end up with just the right grind size for your preferred brewing method.

The benefit of all this “cutting” is that the extraction efficiency dramatically cuts down on brewing time. But that’s not the only reason why we grind coffee.

Smaller grind particles make for a more complete extraction

The smaller particle size makes the distance from its center shorter. This allows not only for a more efficient extraction but also for a more complete extraction of soluble flavors contained within the particle.

Why You Should Not Buy Ground Coffee

A roasted whole coffee bean is a beautiful, protective package that keeps the coffee oils exactly where we want them, namely, inside the bean. As long as you don’t mess with the beans the flavor components, which are very delicate, volatile and water-soluble substances, will be safe. However, break the protective shell and all bets are off.

So, let’s take a look at four reasons why you, as a self-respecting coffee lover, should not buy pre-ground caffeinated or decaffeinated coffee.

1) Contamination

Coffee oils are very delicate, which makes them an easy victim of contamination. Whatever odors are around ground coffee will taint it in ways that will not contribute to your coffee tasting experience.

2) Oxygen

The cells inside the roasted coffee bean contain approximately 1,000 different volatile aromas and flavors. Once ground the volatile aromas are immediately released and they react with oxygen in the air (oxidation). After 15 minutes ground coffee loses about 60% of its aroma.

3) Moisture

Coffee oils are water-soluble. That’s a good thing or we’d have a really hard time trying to get the oils out of coffee beans. This fact, however, poses a great problem for ground coffee. When ground coffee is exposed to moisture in the environment it immediately starts to dilute the oils.

4) Carbon Dioxide Depletion

Increased surface area permits for greater carbon dioxide (CO₂) gas liberation. During the roasting process, a lot of CO₂ is created. Since the bean is porous, some of it is lost during the cooling process. Much of it, however, is retained within the cells of the coffee bean. This CO₂ plays an important role in that it is the main method for getting the essential coffee oils into the coffee once they are released.

The problem is that the increased surface area created after grinding permits greater CO₂ gas liberation. In fact, within 60 seconds of grinding 80% of this gas is released into the air. Wait too long after grinding the coffee and you’ll trade your Ferrari for a go-cart with under-inflated tires.

The Solution: always grind your coffee freshly just before brewing. Follow this rule and you’re one step closer to paradise in a cup.

Three Factors that Can Influence the Grind

There are some factors that can influence the way roasted coffee beans behave when you grind them. Let’s look at the three most important ones here.

1) Roast Level

In general the more light the roast, the more pliable and tenacious the bean. Thus a lightly roasted coffee is going to be more pliable and tenacious than a darker roasted coffee. The reason for this is that the more you roast a coffee, the more moisture is lost during the roasting process, which makes dark roasted beans more brittle.

2) Bean Brittleness

Process Method

The method used to process coffee influences how the beans at the same roast level grind. Coffees processed using the dry process grind differently than coffees using the wet process.

New Crop vs. Past Crop

When the coffee was harvested makes a difference in how it will grind. Usually coffee is available for roasting three to six months after harvest. The goal is to roast the coffee as soon as possible since green coffee gets woodier and woodier with every month that goes by. As you can imagine this is one of the factors that then affects how the coffee ultimately roasts. Coffee beans from new crop coffees produce fewer fine dust particles than from past crop coffees.

Altitude

Coffees grown at higher elevations (about 1,800 ft and above) grind differently than coffees grown at a low altitude (mostly Robusta). The reason for this is that the higher the altitude, the slower-maturing the beans, and therefore the harder and denser its substance.

Arabica vs. Robusta

The difference in cell structure between Arabica and Robusta beans also makes a difference in the number of particles produced after grinding.

3) Air Quenching vs. Water Quenching

When the beans come out of the roaster they must be cooled down immediately to prevent over-roasting. This is called “quenching” in the coffee industry.

Some roasters add water to the air stream that cools the beans to kick off the cooling process. However, “water quenching” (if done improperly and indiscreetly) damages the surface of the roasted beans and can add water lost during the roasting process back into the beans. In contrast, air-quenched coffee is cooled by pulling air through the beans while they are stirred; no water is used during air-cooling.

The takeaway here is that the method that is used to cool roasted coffee can affect the beans in ways that can ultimately result in inconsistent grind particles.

Coffee Grind Chart

One of the many benefits of grinding your own coffee is that you’ll be able to accurately “calibrate” the grind depending on your preferred brewing method and type of coffee. Moreover, once you’ve learned what works with your system of brewing you can easily and consistently replicate it. You will no longer be at the mercy of some generic “one size fits all” grind.

Match the Grind Level to Your Brewing Method

You should always match the size of the grind to the particular brewing method you’ll be using.

The amount of time that water and coffee need to be in contact with each other is directly related to the particle size of the grind. The finer the grind, the more surface area of the bean is exposed to water. The more surface area, the less dwell time is needed. Consequently, if you’re using a brew method that uses a longer dwell time, you’ll need to use a coarser grind.

Following is a chart of brewing methods and their recommended grind level.

If you still have difficulty finding the right grind size go to a local roaster or coffee retailer and ask them to grind you up a small sample of coffee for your brewing method of choice. Prepare coffee with it at home, and if you like the result try to match your grind to it.

The Best Way to Measure Coffee

The best way to measure coffee is by its weight and not by its volume.

The problem we’re trying to overcome here is the following. Coffee beans lose water content and swell in size during the roasting process. The darker the roast, the more water content is lost and the more swelling takes place. Hence 40 dark roast coffee beans from brand X are going to weigh less but take up more space than 40 light roast coffee beans from the same brand X.

So, if you weigh your coffee beans before you grind them you’ll overcome two problems. Firstly, your measurement is going to be far more accurate for you’re taking into account the varying bean densities. Secondly, you don’t have to rely on visual approximation, which you would when using a “standard coffee scoop.”

What’s the best way of getting started measuring your coffee? Invest in an accurate digital scale that measures both in grams and ounces. Make sure it has a way to zero out the scale and goes up in 1-gram increments. Start with the standard measure that is appropriate for your favorite brewing technique.
Over time you’ll then learn to add to or subtract from the weight of the grind according to your personal taste.

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