Factors influencing the quality of coffee

Making coffee sounds simple, but it is not. There is a huge amount of effort and knowledge behind brewing a simple cup of coffee. Some will tell you that making a coffee is easy, like buying a coffee pod, placing it in the machine and pressing a button.

The reality is that the process behind coffee making is much more complex, and it can greatly impact the final result. Let’s examine the secrets, factors, and especially the attention to detail that influence the final quality of a cup of coffee.

Coffee bean quality

No matter how skilled a barista you are, there can be no exceptional coffee without quality ingredients.

There are two primary species of coffee, arabica and robusta, each with its sub-varieties. The coffee served in your cup is often a blend of these sub-varieties.

robusta coffee vs. arabica coffee
Robusta vs. Arabica

Coffee experts, known as cuppers, assess factors such as acidity, body, sweetness, bitterness, cleanliness of the cup, balance, uniformity, aroma, fragrance, aftertaste, etc., to assign a grade to the coffee they taste.

It’s important to note that the grading is subjective and based on sensory elements. However, personal preferences play a smaller role in this case, and the grading depends more on the specific characteristics perceived in each cup of coffee.

It should be clarified that to say which is “the best” coffee in the world would be too simplistic. No coffee professional will ever speak in these terms.

Coffee and its quality would be the combination of several factors that help to shape the final product.

Origin of the coffee bean

The origin of the coffee bean refers to the geographical location or country where the coffee plant is grown, and the beans are harvested. This information is crucial in determining the coffee’s quality, flavour, and overall taste profile.

The growing conditions, such as climate, soil type, altitude, and amount of rainfall, all contribute to the unique characteristics of coffee from different regions.

Variety of the coffee bean

The variety of coffee plant species refers to the different forms and types of coffee plants. These can result from natural selection or selective breeding for specific genetic traits.

They create distinct genetic subspecies within the main coffee species (such as Arabica, Canephora, Typica, Cauti, Caturra, Pacamara, Bourbon, and Liberica).

The altitude of the coffee plantation

The altitude at which the coffee was grown, as well as the location of the farm, are crucial factors to consider. Beans grown at an elevation of over 1,500 meters are considered the finest and are referred to as “hard beans” or “very hard beans.” These high-altitude coffees are also known as high-altitude coffees.

The slow growth at high elevations contributes to the beans’ high density and closed fissures, which are often twisted or zig-zag in shape. On the other hand, beans grown at lower altitudes have a lower density and a semi-open fissure.

Coffee bean harvesting method

The selective manual harvesting method is the best way to ensure high-quality coffee. This method involves handpicking each coffee bean at the exact moment of ripeness, maximizing the chances of producing quality beans.

In contrast, industrial harvesting methods utilize machines that harvest coffee indiscriminately, regardless of the beans’ maturity, leading to a lower quality coffee.

Coffee processing method

An easy way to understand this is to consider separating the seeds from the peel and pulp. To cut a long story short, we can say that:

  • In general, coffees processed by the dry method produce cups with good body, somewhat fruity and chocolate notes, but may have earthy notes, and their cup is less fine.
  • Wet-processed coffees produce cleaner, more uniform, less full-bodied, but brighter, more floral and fruity cups.
  • In the case of coffees treated by the semi-wet method, your cups will provide nuances that combine the two previous methods.

The dry method, which produces natural coffees, is mainly used in countries with little access to water; the wet method, which produces washed coffees, is used in more prosperous regions because it requires abundant water and more complex machinery. The result I find most convincing is the wet processing of coffee.

Roasting method

Roasting is that part of coffee processing that gives the coffee the smell and taste characteristics we all understand as coffee smells and tastes.

Each coffee has its ideal roast, and each method of preparation will require a different roast.

If you don’t understand it, drink a green coffee infusion, and you will see that it is nothing like what we understand as coffee, as it has not been roasted. Depending on how the coffee is made, it will have different characteristics.

Choose a light-roasted coffee
Choose a light-roasted coffee

Natural coffee roasts

Lightly roasted coffee

The light roast has a cinnamon colour. It is the one that best preserves the flavours of the origin, which is why it is usually used for origin or gourmet coffees.

These are coffees with grassy and fruity nuances. It is the ideal roast for filter coffee machines, V60, Aeropress, etc.

Medium roast coffee

The next level is the medium roast. This roast still maintains a considerable level of caffeine but more sweetness. With increased exposure to heat, the sugars in the coffee begin to caramelise, resulting in hints of nuts, caramel and even chocolate.

Medium roast is perhaps the most balanced roast.

This type of roast is suitable for both espressos and filter coffees.

Dark roast

Finally, we have the dark roast. The coffee is much drier, and all its essential oils are extracted. It is a coffee with a very low caffeine content, usually used for espresso machines. In this type of roasting, we get spicy and even smoky flavours. And coffees with less caffeine.

Torrefacto coffee

Torrefacto is not a level of roasting; it results from adding sugar in the roasting process.

A common practice in countries like Spain, Portugal, France and Argentina. The appearance of the beans is much brighter, and the flavour is stronger. A mistake, in my opinion, and in the opinion of many others, as it burns the coffee, and it is a technique that should tend to disappear in the coffee world.

Blend versus single origin

As with wines, the coffee bean offers a universe that comes from the land and its place of cultivation. A single-origin coffee refers to a specific geographical origin, such as a country, a region, or a farm. These are considered special coffees precisely because of their uniqueness.

In contrast to these, blends produce coffees with other qualities, such as varied flavours or a balanced balance.

It is not a question of one being better than the other; they are different coffees, and the aim is to highlight this uniqueness with blends to obtain well-balanced coffees.

Blended coffee is a mixture of different varieties, always with a natural roast. The blend is opposed to the term origin coffee, which is coffee with no type of mixture in the coffee beans.

But if the blend is a mixture, why don’t we use this term in the coffee world? The truth is that blend has traditionally been reserved to differentiate between coffees with a mixture of natural roasted and roasted beans.

Therefore, the term blend has been preferred to differentiate it from coffees that use only natural coffee beans of different origins. In this sense, blends are usually higher-quality coffees simply because they do not contain roasted coffee.

I have already said, and if I have not, let it be noted that the presence of roasted coffee always guarantees a lower quality coffee.

The time between roasting and consumption

So the best advice I can give you is not to leave coffee at home for too long, no matter how well it is packaged. Coffee is not a product you can keep for long periods if you want to enjoy the full quality of the coffee that goes into that package.

The best way to consume coffee is as close as possible to the roasting date of the coffee.


Proper packaging is important. The preservation of coffee has a definite influence on the final cup quality.

This conservation depends on whether the coffee is in contact with oxygen. The essential oils react quickly with oxygen, oxidising the coffee and producing what is known as rancid coffee.

The loss of quality is much faster in ground coffee than in the beans due to the larger surface area in contact with oxygen. Studies have shown that a coffee bean in contact with well-packaged air, after seven weeks, has a significant loss of quality. In-ground coffee, this loss occurs after 8-10 days.

Therefore, use coffee beans and not leave them at home for too long.

To avoid this deterioration in quality, coffee beans are packaged in an inert atmosphere, with a one-way valve that allows the gases released from the beans to escape. This means that the coffee is not in contact with oxygen and can have a longer shelf life.

In the case of ground coffees, the vacuum technique is used, leaving a hard package with minimal residual oxygen.

The hermetically sealed soft package with inert gas and degassing valve can also be used. In the latter case, the ground coffee can be packaged immediately after grinding.

It is also important to remember that once the package has been opened, the loss of quality will be slower if it is kept in a closed container at a low temperature.

In any case, no matter how much packaging technology advances, the best advice I can give you is that if you want quality in your coffee, you should consume it as close as possible to the roasting date.


Amount of water to use for the coffee required for each type of extraction.

We will not go into each specific case, but each extraction system requires a different amount of ground coffee and uses a different amount of water. Our favourite beverage, coffee, in its simplest form, is a mixture of ground coffee beans and water.

And the elements that determine whether we get a sweet, complex and balanced coffee, or an acidic or bitter coffee, depending on the quality of the coffee, the water, and the way we combine them.

This is the relationship between the ground coffee and the water, affecting the strength, mouthfeel and other beverage elements. The taste of a coffee will vary depending on the recipe or ratio you prefer. The amount of each ingredient you use is relevant.

Adding or decreasing the amount of water or coffee can alter the coffee’s flavour, viscosity and other factors.

Some baristas use recipes like “50 grams of coffee per litre of water for that many cups”. But others will talk about ratios, such as 1:14 – 14 ml of water per gram of coffee – or 1:16 – 16 ml of water per gram of coffee.

Whatever the brew ratio, what most baristas try to do is to keep it consistent. This allows them to work more effectively and efficiently.

They also know that if they like how coffee turns out, they will be able to replicate it if they know the amounts of water and coffee they have used.

How do you know what brew ratio you can use?

A filter coffee made at 1:20 would be a weak, diluted cup; 1:10 would be extremely strong.

These are the extremes of the scale; your goal should be to find the right balance for each cup. You will want to perceive the fragrances, the aromas, the flavours and acidity, and all the notes that a refined palate can taste, and you will want to enjoy them.

If you detect flaws in your coffee, you should start by changing one variable at a time and keeping everything else constant. The easiest one to start with is the grind size:

  • Use a finer grind if your coffee is acidic, salty or lacking in body. This will increase the contact area, increasing the extraction speed and allowing you to get more sweet coffee flavours in the cup.
  • If your coffee is too bitter, use a coarser grind. This will decrease the contact area, reducing the extraction speed and preventing too much bitterness from entering the brew.

You can always go to the coffee calculator and calculate the perfect ratio of coffee to water, and it will give you an idea of what ratio of coffee to use for the type of coffee maker you will be using.

Different preparation methods

Filter coffees

are, for many people, the ideal way to taste the nuances of their coffee. With a longer and more diluted drink, the flavours are cleaner.

Espresso coffee

By contrast, espresso is a shorter, more intense drink that is notable for showcasing two or three main flavours. And with this comes a different ideal brew ratio, grind size, extraction time and more.

For espresso, you use an extremely fine grind compared to what you use for filter coffee, a short brew time (often around 25-30 seconds) and very little water; it probably has a ratio between 1:1 and 1:3.

And then you have ristrettos and lungos, shorter and longer versions of espresso.

Immersion coffee: French press type

For immersion coffees (such as French press, Aeropress and coffee cupping), you will need a coarser grind and a longer brewing time. As well as more water than for espresso.

Grind grade

It is the thickness of the ground coffee and plays a fundamental role in the final taste of the cup.

 There are three types of grind: fine, medium and coarse. These three basic types are used depending on the coffee we want and the coffee machine or extraction method we will use.

Fine grind

This is used for coffee machines that use pressure to extract the properties of the coffee. It is used for espresso machines (capsules, automatic and superautomatic).

Medium grind

It is widely used for drip, paper filter, chemex or plunger coffee machines.

Coarse grind

Most commonly used for coffee cupping, French press, and pot coffee.

To achieve various types of coffee thickness, we need a coffee grinder, and we have to choose the one that suits us best, as the wrong size of coffee grind can drastically change the taste of our coffee.

In any case, the consistency of the coffee grind is important, which is why a burr grinder or conical burrs is preferable to a grinder with blades.

With grinding, it is crucial not to make mistakes because the results of making a mistake are tremendous, over-extraction or under-extraction of the coffee.

Learn how to grind coffee according to the coffee machine you use.

The time between grinding and consumption

Once the coffee has been ground, it should be consumed immediately. So, if you want a quality cup of coffee, you will have to grind the coffee just before preparing the cup at the right grind for the coffee machine you are using.

Water hardness

If you buy coffee beans, grind them before brewing and use a good coffee machine. Congratulations, 1% of your coffee will be perfect.

But the truth is that your cup of coffee is 99% water, so there is no need to explain that it is a crucial element for great coffee.

Quality water must have a neutral pH; it must have no taste or smell; we don’t want it to modify the aroma or taste of the coffee; it must have a medium alkalinity and hardness for a good extraction.

Very hard water, i.e. with a high concentration of minerals, will extract too many solubles from the coffee, resulting in an over-extracted coffee with a bitter taste.

It is also an element that damages espresso machines by creating limescale deposits in the coffee machine.

Water with low mineral content, i.e. soft water, will not be able to extract the coffee properly, resulting in an under-extracted coffee with a rather acidic aftertaste.

Water with weak mineralisation, such as that used to prepare baby bottles, is the correct water. Suitably filtered water can also be useful.

According to the Specialty Coffee Association (SCA), an optimal coffee extraction requires a water hardness level of between 40 and 175 mg/L.

Choosing the best water for coffee, we have three alternatives:

  • Filtered water
  • Bottled water

A BRITA-type filter jug will allow us to filter the water, reducing its hardness and eliminating the taste and smell it may have. Alternatively, we can install a filter on the kitchen tap to filter the water directly.

Bottled water for coffee. A popular alternative to filtering water is to buy bottled water. Suppose we are already buying bottled water for drinking. In that case, we can choose bottled water with the right characteristics to make a perfect coffee so we don’t get too confused with weakly mineralised water.

Water temperature

To obtain a good extraction, the water should be between 90 and 95 °C. Suppose the extraction method, such as filtering, is used. In that case, it is advisable to preheat the coffee machine, as the water temperature tends to drop because it is usually at a lower temperature.

This is why we have to preheat the coffee maker so that the water we introduce at 90-95 °C does not drop. We obtain an under-extracted coffee, especially if the coffee is of a light roast, which is typical of these filter coffee makers; if it has a dark roast, this parameter will not affect us so much.

To control the water, you can use a kitchen thermometer to see how much temperature the water loses when it is introduced into the coffee maker. Even if you want to monitor the temperature profile, you can use a thermocouple.


Get the coffee particles to separate, allowing an even water flow through and past them.

Without sufficient turbulence, the water will be unable to evenly extract the flavouring materials from all portions of the coffee bed.

In this situation, some sections of the coffee bed are under-extracted, adding grassy and peanutty flavours to the brew. In contrast, other sections are over-extracted, mixing bitter and astringent flavours into the brew.

Turbulence can be generated through pouring or mechanically, such as with a stirring spoon.

Extraction time

The coffee particles take time to absorb the water, the water dissolves and extracts the soluble material in the particles, and the dissolved material migrates into the beverage.

Because water extracts different chemical compounds from the ground coffee at different rates, the mixture of soluble materials in the beverage changes continuously.

Therefore, controlling the brewing time contributes to an optimal extraction, or at least the extraction you want for the cup, and produces consistent results.

The extraction time varies according to the chosen brewer, filter, and grind grade.

Extraction is simply the method by which we dissolve roasted and ground coffee’s flavours and other components. As the coffee is brewed, hundreds of unique compounds are extracted from the ground beans and passed into the water, shaping your daily cup.

The extracted compounds directly affect the taste and aroma of the coffee. Typically, extracted coffee contains, among many others, the following water-soluble compounds:

  • Caffeine (bitterness)
  • Acids (some of them create sour and sweet flavours)
  • Lipids (viscosity)
  • Sugars (sweetness, viscosity)
  • Carbohydrates (viscosity, bitterness)

By controlling how these compounds are extracted, we can have more control over the cup profile. Coffee compounds are not all extracted at the same time.

The fruity and acidic notes are extracted first, followed by the sweet notes and balance, and finally, the bitterness.

  • An under-extracted coffee will lack the sweetness and slight bitterness needed to achieve balance and taste sour. 
  • An over-extracted brew will be bitter, as the compounds that create the sweetness and acidity will be dulled.

You can create a balanced coffee to your taste by controlling the extraction.

This is just a small introduction to the most basic concepts that influence coffee making, as you can see a challenging and wonderful world worth knowing to enjoy coffee and not just drink coffee.