It can be hard to imagine a world without coffee, especially because drinking a cup of coffee is a widespread societal activity.
And that cup of coffee can be the perfect excuse for meeting with friends, a way of taking a break from the daily routine, or be the best medicine when preparing for an exam.
With coffee being so ingrained in our daily lives, it raises the question, what is it about coffee that makes us love it so much? What do we actually experience while drinking coffee – scientifically speaking?
As I've been writing this article, I have also been enjoying a soothing cup of coffee. So, let’s discover the science behind why we love it so much.
Coffee processing and how it influences coffee experience
There are two main varieties of coffee: Coffea arabica and Coffea canephora (also called robusta), contributing to 75% and 25% of worldwide production respectively.
But, before describing why people like coffee, let's take a closer look at the process it takes to go from a coffee bean to a cup because this process greatly influences how coffee tastes and smells.
Coffee starts as fresh berries called coffee cherries. Though the fruit is called a coffee cherry, coffee is not a type of cherry. Before coffee becomes a drink, the seed must be harvested from the cherry, processed, roasted, and finally brewed.
All of these manufacturing conditions also affect the compounds inside coffee beans and are responsible for the sensory characteristics of coffee beverages (Zarebska et al., 2022).
Coffee trees grow in tropical areas, originating in the Ethiopian plateau, but now they grow in other African, South American, and Asian countries as well.
There are two common ways coffee beans are processed: natural and washed.
The Natural Process
With the natural process, coffee cherries are harvested, sun-dried, fermented (during drying step), and then de-pulped with a machine that removes the fleshy red shell of the beans, releasing the seeds. The natural process takes a longer time and requires more effort, but produces sweet, juicy notes.
The Washed Process
In the washed process, coffee cherries are harvested, de-pulped, washed, and sun-dried. The taste of this type of coffee is lighter than the natural process. It has fruity notes and less acidity because the beans are rinsed.
After the coffee beans are harvested and processed, naturally or washed, they are hulled to remove the parchment (the brownish layer remaining on the coffee beans after drying) and then roasted and later brewed. In other cases, the coffee can be milled for instant coffee.
The coffee aroma and taste
One of the reasons we enjoy this beverage so much is because of its flavor, aroma and aftertaste.
In a cup of coffee, you may experience sweet, roasty, earthy, and smoky notes (Saud and Salamatullah, 2021).
Interestingly, the natural coffee process produces flavors similar to blueberry, strawberry, honey, and tropical fruits because the fruit flesh is retained.
The sugary flesh also contributes to the sensation of fermented flavors and alcohol-like notes.
The washed process, on the other hand, is the most common method and leads to less intense flavors because the fruity flesh was removed during the washed process.
Many coffee drinkers describe it as less acidic than the natural process (Zhang et al 2019).
While coffee processing plays a role in flavor and aroma, it is not the only contributor to coffee's defining characteristics. Coffee bean components also influence how we experience coffee, including its addictive nature.
The composition of coffee
The chemistry of coffee includes components like carbohydrates, proteins, lipids, and caffeine; aromatic components; oils and waxes; minerals and acids. While these characteristics are small and unseen, they can be a big part of how we experience coffee.
However, the variety, origin, time of harvesting, and weather conditions will affect the composition of coffee beans and the distribution of the compounds within.
Carbohydrates are the main component of a coffee bean. In general, higher sugar content is associated with better coffee quality. The main sugars include polysaccharides, like pectin and cellulose, and monosaccharides, like arabinose, mannose, and galactose.
These sugars participate in chemical reactions called Maillard reactions during roasting, affecting the aroma and color characteristics, and providing sweetness to the coffee drink (Seninde et al., 2020).
Proteins are vital to the taste of coffee because they form volatile compounds during roasting. Proteins also influence the color and aroma. In general, higher protein content is associated with higher-quality brews.
Melanoidins are brown nitrogen-containing polymers formed by a reaction between sugars and amino acids under high temperatures and make up to 25% of the roasted coffee, increasing with stronger roasting processes (Pastoriza and Rufián-Henares, 2014).
These complex macromolecules possess multiple health benefits including antioxidant, anti-inflammatory, and prebiotic capacity. Also, because of its concentration in a cup of coffee, melanoidins contribute to the characteristic color and aroma of coffee.
Lipids contribute mainly to the coffee aroma and texture of coffee. During the roasting process, lipids are oxidized. An interesting fact about lipids in coffee is they are responsible for milk floating in espresso coffee.
Coffee beans have a high concentration of the phenolic compound chlorogenic acid, which is associated with coffee's astringency and bitter taste. These become oxidized during the roasting process and provide color to your cup of coffee.
Caffeine is an alkaloid that contributes to the bitterness of brewed coffee. Interestingly, caffeine is resistant to roasting, so you can still enjoy the caffeine taste (Congdon, 2020).
Other alkaloids in coffee include theophylline, trigonelline, and theobromine. Alkaloids have a stimulant effect on us by affecting our central nervous system (CNS) and brain. And each alkaloid can have a different type of stimulating effect (Shriya et al., 2020).
Caffeine can make us feel more alert and awake by affecting our brain in a few different ways.
For example, caffeine blocks the adenosine receptors. Adenosine can contribute to the feeling of sleepiness. So, by blocking the receptor, the feeling of sleepiness is minimized (Fiani et al., 2021).
Other stimulants like theobromine present in coffee can increase your heart rate and cause palpitations. This occurs because theobromine inhibits the breakdown of cAMP, which is an important molecule in many enzyme-mediated processes in the arterial smooth muscle cell (Bas van den Bogaard et al., 2010).
Ultimately, there are so many subtle reasons why we love and need coffee so much. From the processing and roasting to the elements inside, the science behind why we love coffee is interesting, and may even give us more reason to appreciate this drink so much.
Allred, K. F., Yackley, K. M., Vanamala, J., & Allred, C. D. (2009). Trigonelline Is a Novel Phytoestrogen in Coffee Beans ,. The Journal of Nutrition, 139(10), 1833-1838. https://doi.org/10.3945/jn.109.108001
Baggott, M. J., Childs, E., Hart, A. B., de Bruin, E., Palmer, A. A., Wilkinson, J. E., & de Wit, H. (2013). Psychopharmacology of theobromine in healthy volunteers. Psychopharmacology, 228(1), 109-118. https://doi.org/10.1007/s00213-013-3021-0
Barbosa, M. de S. G., Scholz, M. B. dos S., Kitzberger, C. S. G., & Benassi, M. de T. (2019). Correlation between the composition of green Arabica coffee beans and the sensory quality of coffee brews. Food Chemistry, 292, 275-280. https://doi.org/10.1016/j.foodchem.2019.04.072
Bas van den Bogaard , Richard Draijer , Berend E. Westerhof , Anton H. van den Meiracker , Gert A. van Montfrans , and Bert-Jan H. van den Born. (2010). Effects on Peripheral and Central Blood Pressure of Cocoa With Natural or High-Dose Theobromine. Hypertension, 56, 839-846. https://doi.org/10.1161/HYPERTENSIONAHA.110.158139.
Congdon, O. (2020). Brew up some coffee chemistry. Available here.
Duarte, G. S., Pereira, A. A., & Farah, A. (2010). Chlorogenic acids and other relevant compounds in Brazilian coffees processed by semi-dry and wet post-harvesting methods. Food Chemistry, 118(3), 851-855. https://doi.org/10.1016/j.foodchem.2009.05.042
Fiani, B., Zhu, L., Musch, B. L., Briceno, S., Andel, R., Sadeq, N., & Ansari, A. Z. (2021). The Neurophysiology of Caffeine as a Central Nervous System Stimulant and the Resultant Effects on Cognitive Function. Cureus. https://doi.org/10.7759/cureus.15032
Iriondo-DeHond, A., Rodríguez Casas, A., & del Castillo, M. D. (2021). Interest of Coffee Melanoidins as Sustainable Healthier Food Ingredients. Frontiers in Nutrition, 8, 730343. https://doi.org/10.3389/fnut.2021.730343
Mohamadi, N., Sharififar, F., Pournamdari, M., & Ansari, M. (2018). A Review on Biosynthesis, Analytical Techniques, and Pharmacological Activities of Trigonelline as a Plant Alkaloid. Journal of Dietary Supplements, 15(2), 207-222. https://doi.org/10.1080/19390211.2017.1329244
Mohammadi, M. R., Kashani, L., Akhondzadeh, S., Izadian, E. S., & Ohadinia, S. (2004). Efficacy of theophylline compared to methylphenidate for the treatment of attention-deficit hyperactivity disorder in children and adolescents: A pilot double-blind randomized trial. Journal of Clinical Pharmacy and Therapeutics, 29(2), 139-144. https://doi.org/10.1111/j.1365-2710.2004.00545.x
Pastoriza S, Rufián-Henares JA. (2014). Contribution of melanoidins to the antioxidant capacity of the Spanish diet. Food Chem, 1;164:438-45. doi: 10.1016/j.foodchem.2014.04.118.
Saud, S., & Salamatullah, A. M. (2021). Relationship between the Chemical Composition and the Biological Functions of Coffee. Molecules, 26(24), 7634. https://doi.org/10.3390/molecules26247634
Seninde, D. R., & Chambers, E. (2020). Coffee Flavor: A Review. Beverages, 6(3), 44. https://doi.org/10.3390/beverages6030044
Sharma, H. (2020). A Detail Chemistry of Coffee and Its Analysis. En D. Toledo Castanheira (Ed.), Coffee—Production and Research. IntechOpen. https://doi.org/10.5772/intechopen.91725
Shriya, A., Prakhar, A., Mugdha, A., Rachana, M. (2020). Alkaloids as Central Nervous System Stimulants. In Advances In Bioresources, Biodiversity And Therapeutics. Chapter 18. 208-229.
Zarebska, M., Stanek, N., Barabosz, K., Jaszkiewicz, A., Kulesza, R., Matejuk, R., Andrzejewski, D., Biłos, Ł., & Porada, A. (2022). Comparison of chemical compounds and their influence on the taste of coffee depending on green beans storage conditions. Scientific Reports, 12(1), 2674. https://doi.org/10.1038/s41598-022-06676-9
Zhang, C., Linforth, R., & Fisk, I. D. (2012). Cafestol extraction yield from different coffee brew mechanisms. Food Research International, 49(1), 27-31. https://doi.org/10.1016/j.foodres.2012.06.032