What’s In Your Cup of Coffee?

Caffeine chemical composition

Caffeine chemical composition

What is in coffee, and why should we drink it?


Globally we drink millions of cups of coffee every day, but how many of us actually sit down and wonder just what exactly is in our cup of coffee? Well if you do ask yourself this whilst looking into your coffee cup, then we have the answers.


Coffee beans contain many chemical compounds responsible for aromas and flavors, as well as being beneficial to our health. Actually, there’s over 800 compounds identified that vary considerably depending on whether the beans are just green coffee beans or are roasted. Changes to these compounds take place during the processing and roasting of the coffee beans.

Other influencing factors that cause a variation in the compounds are:

  • species of coffee bean
  • geographical location – coffee beans from Mexico and India have higher levels of chlorogenic acids than those from China
  • soil conditions
  • climate and other environmental factors

Despite the above conditions, the components of the coffee bean are pretty much the same and all that differs really are the chemical compound proportions.

What is coffee made of?

Our cup of Joe consists largely of water, in fact, a cup of coffee is 98% water, then there’s the other ingredients:

    • caffeine (of course)
    • sugars
    • carbohydrates
    • proteins
    • lipids
    • organic acids such as chlorogenic acids
    • minerals
    • fibers
    • amino acids
    • trigonelline, which is the alkaloid that causes bitterness


Caffeine, probably the most famous of the chemical compounds found in coffee beans that we all know about.  But there are other chemicals that come under this category being just as vital, such as phenolic acids. Phenolic acids are high in antioxidants so coffee has become one of the richest sources of polyphenols in our diet because of the amount we drink.

Perhaps the most abundant phenols responsible for the high antioxidant activity found in green coffee beans are chlorogenic acids (CGAs). However, during roasting a large percentage (approximately 80%) of chlorogenic acids are destroyed, but this depends on roasting time and the coffee beans themselves – Arabica beans tend to have lower levels of chlorogenic acid than Robusta.

Structural changes within the coffee bean occur during the roasting process leading to other antioxidant compounds and melanoidins being synthesized. Alongside high antioxidant activity, melanoidins also have antifungal, antimicrobial, antihypertensive, and anti-inflammatory properties. These properties may help in warding off fungal infections, inflammation, and other health problems.

Polyphenols and phenols help your body’s cells fight against oxidative damage due to their ability to increase plasma antioxidant activity. Studies suggest this can help lower the risk of degenerative diseases like Alzheimer’s Disease if 3-5 cups of coffee are drunk every day.


Lipids are organic compounds and examples are fats and oils which play a vital role in the overall quality of your coffee.  These compounds are mostly made up of triglycerides, sterols, and tocopherols.

Arabica coffee beans have been found to contain a higher percentage of lipids than Robusta, averaging 15-17% and 10-11.5% respectively. Studies found a direct correlation between higher lipid levels and coffee quality, so this is another reason why quality differs between both species of coffee bean.

Lipids also contain diterpenes, which are fatty acids that can make up to 20% of the lipid content. Studies have shown that diterpenes can have both positive and negative effects on health. Kahweol and cafestol are two types of diterpenes found in unfiltered brews and studies have indicated can raise serum levels of both total and LDL-cholesterol.

The method of brewing, such as filter brewing reduces the lipid content by a large amount and only retains 7 milligrams of lipids, whilst boiling and espresso methods contained between 60-160 milligrams per 150 mL cup.

However, these fatty acids contain a large concentration of coffee flavors and that’s why you may have noticed the difference in mouthfeel when you drink a filtered coffee compared to a French press coffee.


Acids are vital to creating a good cup of coffee and over 30 different organic acids have been found to be in roasted coffee beans. Each of these different acids plays a role in how the coffee will taste and the level of antioxidants found.

The most well-known and probably most important is chlorogenic acid (CGA), which has high antioxidant levels in green coffee beans.

Chlorogenic acids were discovered in 1932 and were found to contribute largely to the acidity in coffee. Dark roast coffee has the lowest levels of chlorogenic acid.  So it goes without saying that lighter roasts have higher levels and higher acidity profiles. However, up to half of chlorogenic acid is destroyed during roasting leading to two byproduct formations: quinic acid and caffeic acid.

Quinic acid plays an important part in flavor and cup quality; therefore, a key player in acidity and astringency of your cup. However, quinic acid also decomposes during roasting so the flavor and acidity of the coffee will be affected; the more a coffee degrades, the higher the level of quinic acid. You’ll find dark roasted coffee is high in quinic acid, as is coffee that is stale or brewed or roasted some time ago…resulting in that sour stomach feeling.

Caffeic acid is micronutrient antioxidant belonging to compounds known as polyphenols. Polyphenols, as mentioned above, are high in antioxidant activity and are also found in red wine, green tea, and dark chocolate, to name but a few.  You could say it’s beneficial to health, as it’s not only high in antioxidants but also has anti-carcinogenic properties as well.


Coffee has been found to contain the following minerals:

  • phosphorus
  • potassium
  • manganese
  • magnesium
  • trace elements of about 30 other minerals

Even though coffee contains some of the vitamins and minerals we need, it nowhere near provides the amount we should be getting daily.

According to Harvard Health Publications, a cup of coffee contains about 7 mg of magnesium, but we should be getting (420 mg for men and 320 mg for women).


Alkaloids are important compounds and the most well-known one is caffeine.  There is also another important less well-known alkaloid called trigonelline. Trigonelline is present in both green and roasted coffee beans and is important in the development of flavor and aromas.

Trigonelline deteriorates during roasting forming various byproducts, one important one being nicotinic acid, or vitamin B3 – more commonly known as niacin. Niacin has a great number of health benefits such as its ability to assist in repairing DNA damage and lowering cholesterol.

One cup of coffee can contain up to 3 milligrams and the daily recommended dietary allowances are 16 mg a day for men and 14 mg a day for women (Medlineplus.gov).


Comments are closed