The reason your coffee tastes like coffee
For such an unassuming looking ingredient the coffee beans chemical make-up is surprisingly complex. With around a thousand chemical compounds and more being discovered on a near-annual basis, what reactions and processes lead to coffee taste and flavor?
Coffee’s taste and its flavor largely depend on the roasting style used. During roasting carbohydrates and fats turn into aromatic oils while roasting also breaks down or builds up various acids that give coffee its taste.
Two major processes take place during coffee roasting which forms the majority of the flavor and aroma compounds found in your coffee cup.
The Maillard Reaction
Put simply, the Maillard reaction is the chemical breakdown of sugars and amino acids, which results in the browning of food during cooking! It’s what gives color to toast, caramelization to crème brûlée, and the roasted color to your coffee beans.
The reaction occurs upwards from 280°F / 140°C where sugars react with a group of amino acids to create hundreds of new, different flavors. For coffee, it creates those roasty, malty, and even fruity flavors.
Above 330°F / 170°C, caramelization kicks in and starts to use up the remaining sugars and gives color to the roasted beans.
Did you know
As well as flavor, melanoidins formed in the Maillard reactions also play an important role in forming and stabilizing crema in espresso and provide body to brewed coffee. They may also provide some of coffee’s health benefits, especially antioxidant and anti-inflammatory activity
The second major process that occurs during roasting is the Strecker degradation – a chemical reaction whereby amino acids combine with carbonyl compounds resulting in the creation of important flavor compounds ketones and aldehydes.
Formed by the interaction of oxygen and carbohydrates, ketones are responsible for 21.5% of coffee aroma while aldehydes contribute 50.7%, and with dozens of different types of ketones and aldehydes in both green and roasted coffee, flavor and aroma combinations are endless.
A word on Acidity
Acidity in coffee relates to the many nuanced levels of flavor that give dimension to a cup of coffee. Varying levels of acids within the beans, formed during the cultivation process and influenced by the plants’ terroir (growing conditions: soil, climate, and elevation), lend individual flavors to coffee and, if well balanced, provide a complex composite that gives a zing to its taste.
The majority of coffee’s acid content is made up of chlorogenic acids and citric acids, which add brightness to a cup in small to moderate quantities but sour notes in higher quantities.
Also important are malic, acetic and phosphoric acids. Malic acids lend fruity apple notes, acetic acid gives distinct wine-like flavors and phosphoric acid although adding no flavor gives a sparkling, biting acidic taste to a brew.
These reactions produce hundreds of possible outcomes, all of which produce a significant range of flavors that can be found in your cup.
Depending on your roast you many find floral, sweet, or honeylike flavors in others you will find bitter, nutty or burning! Similarly, cups can be buttery, spicy and herbaceous to fruity or minty.
If you’re not sure how to classify the tastes and smells you’re experiencing with your coffee, the Specialty Coffee Association (SCA) Taste Flavor Wheel is a great resource to help you enjoy your brew more.
Illy, E., Navarini, L., 2011. ‘Neglected Food Bubbles: The Espresso Coffee Foam.’
Moreira, AS., Nunes, FM., Domingues, MR., Coimbra, MA., 2012. ‘Coffee melanoidins: structures, mechanisms of formation and potential health impacts.’
Merritt, C., Bazinet, M., Sullivan, J., and Robertson, D. 1963. ‘Mass Spectrometric Determination of the Volatile Components from Ground Coffee.’ Journal of Agriculture and Food Chemistry 11