Coffee's Chemical Composition
On this page we’ll outline the chemical compounds that can be found in coffee and detail how important compounds, like caffeine, interact with processing and roasting to shape the overall flavor of the coffee. This part of the guide should leave you with a good sense of the important chemical compounds present in coffee and what you need to know about their influence on taste and quality of coffee.
Coffee Molecules and Ingredients
The caffeine in coffee interacts with the adenosine receptors in the brain to provide energy. This is why many people drink coffee in the morning to help them start their day.
Caffeine also blocks adenosine receptors, which is why drinking too much coffee can make you feel jittery.
When you are awake, the neurons in your brain are continually firing, and a by-product of this firing is adenosine, a biochemical compound that is a neuromodulator for the central nervous system.
Your nervous system receptors are constantly monitoring your levels of adenosine, and when they get too high, your brain will slow down neural activity and dilate the blood vessels, making you feel sleepy or crave rest.
Caffeine has a similar molecular structure to adenosine – notably, two nitrogen rings.
This similarity in structure means that caffeine can bind to your nervous system’s adenosine receptors without activating them, effectively blocking the receptors from detecting the levels of adenosine and, therefore, keeping you alert even if those levels may be elevated.
While you are awake, the neurons in your brain are firing. As a result of this firing, adenosine is produced, which is a neuromodulator for the central nervous system.
Your nervous system has receptors that continuously monitor your levels of adenosine. When they get to a level that's too high, your brain slows down neural activity and dilates your blood vessels. This ultimately makes you feel sleepy or crave rest.
Chemical Structure and Impact of Caffeine
It's no secret that caffeine, which is found in coffee and tea, can help to increase alertness levels.
This is because caffeine has a molecular structure similar to adenosine, a chemical that binds to nerve receptors.
The similarity between caffeine and adenosine means they can bind to the same receptors without activating them, blocking the receptors from detecting adenosine and keeping you alert.
Pure caffeine is a white, bitter and odorless powder.
It is an organic chemical that belongs to a class of chemicals called purine alkaloids. Caffeine occurs naturally in several plant species and is used in beverages in addition to coffee including cocoa, tea, and yerba mate.
Caffeine can act as a natural pesticide, even being used to protect plants from insects. However, it also has a positive impact on the memory of some insect pollinators such as bees and butterflies.
In a study conducted at the University of Northumbria in England, researchers found that honeybees were three times more likely to remember a floral scent after ingesting caffeine. The bees returned to the plants with nectar containing caffeine when given the choice between two types of nectar.
Caffeine also has mild diuretic properties and functions as a mild stimulant on the nervous, circulatory, and respiratory systems.
Once caffeine is consumed, it is absorbed through the gastrointestinal tract and remains in your body for between four and six hours. Once it reaches the liver, it is metabolized into three compounds.
Paraxanthine, Theobromine, and Theophylline
Most of the caffeine will turn into a compound called paraxanthine, which increases the breakdown of lipids in the bloodstream.
A smaller amount will turn into theobromine, which dilates blood vessels.
A tiny amount becomes Theobromine is an alkaloid that occurs naturally in some plants, such as the cacao plant. It has effects similar to caffeine but milder. When decacacao is ingested, a small amount of it becomes theophylline. Theophylline, in turn, relaxes smooth muscles (the kind found in the digestive tract and respiratory systems).
The ultimate outcome of all this is that the heart rate noticeably quickens, and your muscles receive more blood. However, skin and organs actually receive less blood and the caffeine also causes the liver to release glycogen.
How Caffeine Increases Mental Alertness
Because caffeine is both fat- and water-soluble, it passes easily through the so called blood–brain barrier.
Also, caffeine stimulates the production of adrenaline and increases neurotransmitter levels, such as dopamine, serotonin and acetylcholine. These neurotransmitters are responsible for mood changes and other things in the body. Ultimately caffeine has a similar effect on the body as adrenaline, increasing breathing and heart rate.
Coffee is a popular beverage worldwide, and arguably the biggest reason for its popularity is its ability to increase mental alertness with practically no negative side effects.
That said, caffeine has actually been tested and proven to offer numerous other health benefits. For instance it's been linked to increased metabolism and also correlates to a decreased risk of diseases like diabetes, cancer and heart problems.
Is Caffeine Addictive?
While caffeine is not addictive, consuming more than four to five cups of coffee a day can lead you to developing a mild physical dependence.
This means that if you stop consuming coffee (suddenly) you may experience withdrawal symptoms like headaches, fatigue, and irritability.
Those symptoms typically abate within a few days.
If coffee consumption is reduced more gradually instead of halted abruptly, most withdrawal effects can be avoided or at least significantly mitigated.
The Chemical Components Found in Coffee
Believe it or not, there are more than eight hundred chemicals that can be found in coffee beans, with many of them impacting the flavor profile and health benefits of the coffee.
Green coffee and roasted coffee contain a very different set of chemical components. This is because there’s significant transformations that take place when green coffee beans are roasted and processed.
Additionally, the chemical components of coffee will vary considerably depending on the specifics, the environment and the climat the coffee beans are found in.
Having said that, there are some basic components to the chemical makeup of coffee that are common to both green coffee beans and roasted coffee beans, with the principal difference found in the degree in which those components are present.
A coffee bean is fundamentally made up of water, sugar, carbohydrates, various proteins, minerals, caffeine and alkaloids that determine the bitterness of the taste.
One category of these chemicals is Phenols and Antioxidants.
Phenols and Antioxidants
Of course most people are aware that coffee beans will contain caffeine but equally important chemicals include phenolic acids which are famous for containing a high degree of antioxidants.
In fact, the antioxidants found within are extremely rich sources of polyphenols and they also contain flavonoids and lignans.
The most present of these phenols are chlorogenic acids, which make up most of coffee’s antioxidant content.
A significant volume of the chlorogenic acids, a very well known antioxidant, that are found in coffee are actually destroyed during the roasting, leaving only about 20% of what could originally be found in the green coffee bean.
Interestingly, studies will still show that roasted coffee beans have a higher level of antioxidants than their unroasted green bean counterparts1.
This is because even though there is a loss of chlorogenic acids, roasting coffee causes the coffee bean to undergo a series of structural changes.
One of these changes includes the synthesizing of melanoidins, which are very strong antioxidants. Melanoidins also have strong antifungal and anti-inflammatory properties.
The Maillard Reaction
What causes these structural changes and newly synthesized antioxidants? This process is largely attributed to something known as the “Maillard reaction”, named after the French Chemist Louis Camille Maillard who first described the concept in 1912.
This refers to a chemical reaction that takes place between sugars and amino acids, and can often be witnessed as the familiar “browning” we see happen to many other foods during cooking.
The Maillard reaction is a significant process when cooking anything because it creates many new compounds that directly impact and sometimes dramatically change the flavor profile of food.
The green Robusta bean has more antioxidants than the Arabica, but because the antioxidant profile is vulnerable to the damage brought about through the roasting process it’s surprisingly Arabica that ends up having more antioxidant content overall once the coffee beans are roasted.
Lipids
Lipids are organic compounds like fats and oils, and they have a large role to plat in the quality of the coffee.
Mostly they are made up of triacylglycerols, sterols, and vitamin E.
Up to 20 per cent of the lipid content is typically composed of Diterpenes, which are a type of fatty acid.
The two types of Diterpenes found in unfiltered coffee (in significant quantity) are cafestol and kahweol and they have both been shown to increase serum cholesterol in humans.
Paper filters will actually remove most of those compounds which is why those at risk of cardiovascular problems are typically advised to lower the amount of unfiltered coffee they drink or only drink filtered coffee.
On the other hand, some research has shown that both cafestol and kahweol have the potential to lessen the effect of some carcinogens.
It’s important to keep in mind that many of the fatty acid compounds are at risk of decomposing when they’re stored above appropriate temperatures. This decomposition can lead to the coffee developing off flavors.
Also it’s good to know that the type of coffee brewing employed can impact and reduce the overall lipid content of coffee.
Filtration will usually deplete the total lipid content quite severely. In fact filter brewing methods have shown that they retain only 7 milligrams of lipids. In contrast, boiling and espresso methods of brewing will allow the coffee to retain between 60 - 160 milligrams per cup.
As mentioned, a good amount of the coffee flavor is contained and influenced by those fatty acid compounds, which explains why filtered coffee can have such a different flavor profile vs the same coffee when brewed differently.
The final roasted version of Arabica contains more lipid content than Robusta, which also helps explain why it’s generally considered to result in better quality coffee.
Acids
You can find more than 30 acids in a roasted coffee bean, with each contributing a different flavor and antioxidant.
Specifically, chlorogenic acids are arguably the most prominent acid you’ll find and they make up a huge percentage of the acid content in any given cup of coffee.
Roughly ½ of the chlorogenic acids get destroyed during the roasting process and result in the production of quinic acid and caffeic acid.
Quinic acid can be critical in determining the coffee quality and flavor as it helps to form important compounds throughout the Maillard reaction.
The impact of quinic acid extends to the ultimate bitterness of the coffee.
Caffeic acid can also be found in wine and it’s most notable flavor characteristic is its acidity.
It’s really the balance of the acidic content found in the coffee that will dictate how it will taste. A correctly balanced coffee will prevent it from tasting “flat”, for lack of a better word.
Alkaloids
The first alkaloid of note is called trigonelline. Trigonelline is a bitter alkaloid you can find in the green and roasted coffee bean. It helps to determine the aromas and flavours while also producing a number of health benefits.
Trigonelline deteriorates during the roasting process and this leads to the production of a number of different compounds. Those compounds include something called nicotinic acid, which is better known as vitamin B3.
Minerals
As far as minerals go, coffee contains roughly 30 but the more notable ones are the following:
- Potassium
- Phosphorus
- Magnesium
- Manganese
Coffee is not recommended as a beverage that can be relied on as a significant source of minerals because the mineral content found within can differ widely according to the type of bean and the corresponding environmental conditions.
Did You Know?
Caffeine’s chemical structure is very close to that of purine (purines are the most common nitrogen-containing molecules found in nature). The chemical formula is C8H10N4O2 and it happens to be one of the very few legal and barely regular psychoactive drugs you can find.
FAQ
What are the 3 steps of the Maillard reaction?
The three stages of the Maillard reaction are Early, Advanced, and Final.
In the early stage coffee bean color remains unchanged and does not absorb any U/V light. Sugar-Amine condensation and Amadori rearrangement reactions take place.
In the advanced stage the color may yellow with as UV absorption kicks in. Sugar starts to degrade and fragment.
In the final stage coffee beans move from yellowish to brown, condensation of aldols and sugars occur along with the formation of new chemical compounds. The sum total of this reaction is the production of Melanoidins, which are compounds developed from the destruction of sugars and proteins during the process.
How many molecules are there in coffee?
There are more than 1,000 chemical compounds in coffee.
How does caffeine give you energy?
Caffeines promotes alertness by blocking the effects of a brain chemical that ordinarily makes you feel tired and less alert while also triggering your body to release adrenaline.
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4665516/
Deeper Dives
More In Depth Articles Relating to Chemical Compounds in Coffee:
Coffee Phytochemicals
Caffeine in Coffee Chemistry
Theobromine in Coffee Beans
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