Unlike other types of drinks, the visual evaluation of coffee is not based on its clarity, intensity or nuance. Nevertheless, its appearance can give useful information about the quality of the brand used and the skill of the person who prepared it. This explains why tools such as the cup and the goûte caffé, though lacking transparency, can show the most important characteristic of all: the crema.
The crema is tested according to:
- its color and, in particular, its intensity and its nuance
- its persistence, i.e. the time it takes for the crema to break up
The color of the crema comes mainly from sugar that has been caramelized during the roasting process, and partly from phenols that have been oxidized by the heat applied during the same process. The intensity and nuance of color can vary from deep hazel to dark brown with reddish shades and light hazel streaks, if the coffee has been prepared using an Arabica blend.
It can be pale hazel in the case of underextracted coffee, or mahogany in the case of overextracted coffee. If the coffee has been prepared using a Robusta, the crema is darker and has a grayish shade. The consistency of the crema is given by proteins, fat, sugar and by other viscous substances emulsified by gas during the preparation of coffee. The same components affect the duration of the crema i.e. the crema that remains in the inner part of the cup after the coffee has been drunk.
A good espresso coffee has a compact, fine-grained, long lasting crema and fine buttonhole. These characteristics are important because they are strictly related to the sensorial appreciation of high quality crema, and they are also vital to keep the aroma within the coffee until it is drunk.
During the sensorial evaluation of coffee, the comparison between the aroma and our olfactive sense is of paramount importance. This is easily explained. Coffee aroma is made up of some thousand molecules, which, according to their interaction, create sensorial maps. For the taster, such maps reveal important information about the origin of the beans that make up the blend, and about the skill of the person who prepared the drink.
Our olfactive sense is complex; a mucous membrane of a few square centimeters is able to recognize an infinite number of different molecules sending signals to the brain. If there is a weak spot, it is that our brains pay less and less attention to the signals sent by our olfactive organs. Our ability to retrieve olfactory signals is weaker than the one that allows us to retrieve images.
We are almost always able to retrieve an image, but the same can’t be said of a smell. For example, when you hear a person’s name, your brain will conjure up a picture of his/her physical appearance, which allows you to describe him/her in detail. We will only remember the name of a flower by its scent if the scent is present at the time.
Only through constant training can we store such information, the key to which will nevertheless remain outside ourselves. Not only is the aromatic profile hard to recognize, but it is extremely difficult to communicate. It has been likened to a badly tuned radio, broadcasting in a foreign language. In other words, the most important part of our sensorial analysis is also the most difficult to be measured objectively.
In the case of coffee, things are not any easier: over 800 types of molecules able to stimulate our olfactive sense are formed, first by the natural synthesis of the plant, then by the stages the green beans undergo before the final roasting. Each molecule carries a signal that, in combination with others, creates something completely new and always different.
If 26 letters of the alphabet allow us to write innumerable poems, and the world can write its music from 7 musical notes, how many different signals can 1000 active molecules carry? The olfactive organ is the only one called to work twice: once during the direct act of smelling, and again after swallowing the drink through the back of the throat (the aftertaste).
In the first case, the molecules, which are more volatile because of the high temperature, reach the mucous gland in the nasal septum. By becoming soluble in the mucus, they stimulate the receptors. The taste common to all types of coffee is that of the roasting; only afterward can we detect the characteristics of a good blend and expert preparation.
After swallowing our sip of coffee, its temperature decreases to that of the human body. Consequently, we would expect our perception of the aroma to be reduced, but two phenomena change this. First, the espresso settles on the oral mucus, which increases the evaporating surface and enables us to better segment the taste. Secondly, the fat present in coffee makes this process last for a long time, which allows the taster to carry out a detailed examination, and the consumer to enjoy the taste of this drink after swallowing it. All this is possible because the aromatic components reach the olfactive mucous through the back of the throat.
When we are directly smelling coffee, we evaluate the intensity and degree of the aroma (the amount of positive and negative odors); the intensity of the roast that typifies the various degrees of roasting; and the fineness or preciousness of the fragrance. We evaluate negative and positive odors through the back of the throat.
The negative odors are caused by faults in the green coffee, or improper roasting, or when the final beverage is made. Positive odors are all those sensations that we can perceive, thanks to the good quality of the coffee beans and the ability of all the operators throughout the production chain. These are both distinct from richness, which can best be described as the multitude of positive sensations offered by a good espresso.
When dealing with this fundamental subject, we have used the word “aroma” to describe olfactive sensations and sensations perceived through the back of the throat. According to the ISO methodology, the word aroma only refers to the latter.
Positive and negative olfactive sensations, which are easily perceived when smelling an espresso, are defined in Italian semantic tables and codified by the International Institute of Coffee Tasters.
The following list is certainly not an exhaustive one. Throughout the world, many other lists have been compiled, according to the relevant country’s culture and tasting methodology. The appendix contains the list compiled by the International Coffee Organization (ICO).
The dominant characteristic of coffee caused by particular components being formed as a result of sugar being transformed during the roasting process.
This is the typical aroma of good cocoa, which verges on vanilla. It is one of the best and most desirable aromas.
Reminiscent of fresh flowers even though the single fragrance is difficult to recognize. It is the typical aroma of good coffee. It is particularly evident in good washed coffee that has been enriched by the action of certain microorganisms active during the roasting process.
Reminiscent of fresh fruit. It is typical of washed coffee that has been badly roasted.
Complex characteristic resulting from a particular molecule that starts during Maillard’s reaction – a phase of the roasting process.
Denotes poor quality beans.
Stinker (Rotten Flowers)
This is an English term used to identify a group of unpleasant smells that are typical of rotten flowers. It comes from the involuntary fermentation of decomposed berries.
This reminds us of the smell of fresh grass and green twigs. It is caused by particular aldehydes. It is considered to be a positive characteristic if it falls within certain parameters.
This is considered to be a negative characteristic.
Riato (Rio Flavour)
This is a negative characteristic, reminiscent of wine corks, and is caused by fenic acid due to the presence of very small particles of tricloanisole.
This reminds us of the smell of ham that has been sliced and left for a time. It is caused by fat oxidation. It is particularly evident in old coffee, coffee that hasn’t been packed properly, or coffee that has been left in the grinder for a long time.
This is caused either by dirty filters or by dirty filter holders.
This is usually considered to be a negative characteristic and is due to the presence of diacetyl – a specific ketone.
This scent is absorbed by green beans that have been stored in wet jute sacks
Taste is one of the poorer sense organs. We can perceive two sets of sensations when sipping coffee: true taste sensations and tactile sensations. There are only four tastes in the first group: sweet, bitter, acidic and salty. Tactile sensations are heat-related, astringency and physical consistency.
Papillae (taste buds) on the tongue are small organs able to recognize tastes. The taste buds on the tip of our tongues recognize sweetness, the ones on the side of the tongue, saltiness, and the ones on the border, acidity. Bitterness is recognized by the papillae on the bottom of the tongue.
Tactile sensations are very important as they help to determine a coffee’s profile. The temperature of the liquid gives the heat-related effects in espresso. Even though the habit of drinking cold coffee is spreading rapidly, espresso must be drunk hot, but not too hot. At 65 degrees centigrade, we feel pain, and pain seriously compromises taste. Astringency is caused by the precipitation of a saliva protein and by specific polyphenols, which are present in high quantities in certain types of coffee. These polyphenols can attach themselves to the proteins of our oral membrane.
As a consequence, we feel a sense of dryness and sometimes our mouth sets (as if we were eating an unripe persimmon). Viscosity gives us an almost opposite sensation. This depends on the presence of microscopic solid particles and colloids- molecules of high molecular weight – which give sensations of roundness and thickness.
If such sensations are too strong, they give us an unpleasant feeling of greasiness. In coffee, the presence of sugars, proteins, fats and colloids produce mellowness, while tannic substances give astringency. When mellowness is accompanied by a well-balanced acidity, we experience a coffee with a good body and an excellent composition. This is very important as the substances that give coffee its composition and body are also good fixing agents of the scent molecules, which are slowly released, and prolong the pleasure of drinking it.
This is caused by residue sugars in roasted coffee. Over-roasting the beans diminishes sweetness and decreases the amount of glucides that, in green coffee, range from about 10% to a mere 2%, which is considered the optimum percentage.
Acidity is caused by organic acids that measure about 7% before roasting and 4-5% afterwards. Coffee becomes less acid the more it is roasted.
This is usually felt on the bottom of the tongue. It is present in coffee and is considered a positive characteristic if it stays within certain parameters. It comes from sugar compounds during the roasting process, from burnt wood compounds, and from caffeine. It is more evident in Robusta.
Earthy and Woody
This sensation is caused by the diminished ability of saliva to lubricate. It is usually associated with tannin – a strongly bitter taste. Sometimes small particles, which taste of dirt, can emphasize these characteristics.
This sensation is caused by the reduced ability of saliva to lubricate. Substances of tannic origin (polyphenolic acids) are responsible for the degradation of a saliva protein that allows lubrication.
This is directly in proportion to the quantity of microscopic solid substances, and it increases with the increase of sweetness and fats. It decreases in the presence of bitterness and acidity. Smoothness is usually to be found in a rich, creamy espresso. It should be full, rich, vivid and fragrant, and the various tastes should be progressively distinguishable to offer tasters a succession of sensations.
There are two species of coffee plants that are traded commercially and enjoyed as a beverage. They are Coffee Robusta and Coffee Arabica. Robusta coffee is commonly used in the processing of instant and commercial blend coffees. These beans have twice the caffeine content of Arabica coffees and tend to have a stronger flavor and heavier body. Arabica coffee is more delicate and flavorful than Robusta coffee and represents 75% of the world’s coffee production. However, only about 10% of these beans qualify as specialty coffees sold by gourmet retailers such as Moxie Java®.
Although technically an evergreen shrub, the coffee plant is generally referred to as a tree because it may grow to more than 20 feet high if it is not pruned. Coffee beans are actually the center of a red cherry that blossoms on this plant. The ripe red berry consists of several layers. These layers are:
- An outer red skin
- A sweet pulp
- A parchment skin
- A silver skin (protective membrane)
- Two green coffee seeds (beans)
The cherries grow for six to nine months before they are ready to be picked and processed. The care and harvesting of the coffee plant are much longer. The Arabica plants require very high demands in climate and weather and time in order to grow and produce quality coffee for approximately 25 years. Arabica beans are grown between the Tropic of Cancer and the Tropic of Capricorn in areas where the temperature range is between 68 and 75 degrees Fahrenheit. Arabica coffee grows at altitudes of 3,000 to 6,000 feet above sea level. Shade is also necessary to avoid higher temperatures and excessive sunlight.
To provide this protection, coffee plants are often grown on mountainsides that receive a certain amount of sunlight or trees are strategically planted nearby the coffee plants. Only 600 to 800 coffee plants are planted per acre and take about five years before the first crop can be picked. The number of harvesting seasons yielded by a coffee plant is dependent on rainfall. If a region has one distinct rainy season, such as Brazil, then it has only one harvesting season. However, if a region is in an area where rainfall is evenly distributed throughout the entire year, it is common to see flowers, immature berries, and ripe cherries on the tree at the same time.
Picking cherries is a very labor-intensive process and is primarily done by manual labor rather than machines. Picking by hand yields better results due to the more selective process that is involved. In regions with all-year rainy seasons, “selective picking” is the predominant means of harvesting a crop. In this method, workers will typically return to the same tree three, four, even six times to pick all of the ripe cherries. In areas with distinct harvest seasons, “strip picking” is used to pick the ripe cherries. This method involves drying the cherries on the branches and then stripping them away from the branches with one rapid movement. It is possible to get 35 pounds of roasted coffee from 200 pounds of picked cherries. This is only 1 1/2 to 2 pounds of roasted coffee from a single coffee plant.
After the beans are picked, they are processed in order to remove the outer layers of the cherries. Two processing methods are utilized to remove the various layers:
This method utilizes a machine to remove the cherries’ outer skin, removing most of the pulp and exposing the parchment-covered beans. To remove the sticky coating called “mucilage,” the beans are placed in large tanks of water to ferment for 24 hours and are then thoroughly washed. The clean beans are either dried in the sun for up to three days or dried by machine. The last step of processing incorporates a hulling machine to remove the parchment and silver skin, exposing the green bean.
Beans processed in this manner usually range in color from blue/green to gray/green. These beans tend to command higher prices due to the additional labor and equipment involved in the process. Due to the cleanliness of the water, they also tend to have a cleaner flavor in comparison to beans processed by the dry method.
Countries lacking sufficient water supplies, such as Brazil and Ethiopia, most often use the oldest method of processing – the dry method. Ripe cherries are allowed to partially dry while still on the tree. Once picked, they are spread out on large patios and dried in the sun. The drying beans are raked and turned several times a day and continue to dry for two to three weeks. Once dried, the beans are put through the hulling machine to remove the parchment and silver skin.
Dry processed coffees are greenish to brownish in color and are generally heavier in body. The coffee industry commonly refers to these beans as “naturals.”
After processing, the beans are ready for sorting and grading. Beans are sorted by size, shape, density (hard or soft), and color. Peaberries are separated from normal beans and are graded separately. A peaberry occurs when a ripened berry produces a single bean. This single bean is smaller and more rounded than the normal bean. With Arabica coffee, these highly desirable Peaberries occur approximately 10% of the time.
Once sorted, coffee is graded for export. Each producing country sets its own standards for sorting, grading, and labeling coffee beans.
The criteria for grading coffee include:
- Altitude of growth
- Age of the beans
- Flavor characteristics of the brewed coffee
- Number of physical defects (black beans, broken beans, etc.)
Before the new coffee crop is shipped to foreign shores, the green beans are packaged in jute, hemp or sisal bags. Bags are packed and sewn closed weighing 132 pounds (60 Kilograms) or 152 pounds (69 Kilograms). Many countries store the bags in ventilated warehouses, which protect the green coffee from absorbing moisture and strong odors.
For export purposes, the International Coffee Organization (ICO) developed a classification system that groups coffees according to three main criteria:
- Species (Arabica or Robusta)
- Processing Method (Wet or Dry)
- Altitude of Growth (Low, Medium, High Grown)