What Products are Generated by the Caramelization Reaction During Roasting? What Happens When Caramelization is Excessive or Insufficient?

FrontStreet Coffee: Brief Overview of Caramelization in Coffee Roasting

Caramelization Reaction

The sugars in coffee beans undergo caramelization at roughly 170-200°C - a range that overlaps with the melting point of sucrose (185°C) and the temperatures of the first-crack phase in roasting.

The products of caramelization fall into two groups:

Dehydration products of sugars, which are caramel or sauce-colored.

Decomposition products, mainly volatile aldehydes and ketones.

In short, caramelization produces roasted aromas, caramel flavor, and brown color, along with other aromatic substances such as maltol, cyclotene, and furan compounds. Many of the same compounds can be found in foods like red wine, fruit juice, and cream.

But more caramelization is not automatically better. Pushed too far, it leads to carbonization and a harsh, throat-grabbing cup. Too little, and the aroma turns monotonous and bland, lacking complexity.

Volatile and Non-Volatile Compounds

You may have heard that roasted coffee contains both volatile and non-volatile compounds. Broadly speaking, volatile compounds are the source of coffee's aroma, while some non-volatile compounds carry its flavor. So what exactly are they?

Volatile compounds are organic chemicals with high vapor pressure at room temperature. Many form during the Maillard reaction in the development phase of roasting, and when they are released we perceive that distinctive coffee smell. They include:

• Aldehydes: add fruity, green-plant aromas.

• Furan compounds: contribute caramel flavors.

• Pyrazines: carry earthy odors.

• Sulfur-containing compounds, including 2-furylthiol. Some smell like classic "roasted coffee beans," while others are undetectable in isolation - methanethiol, for example, smells like rotten cabbage.

• Guaiacol: adds smoky, spicy notes.

Carbon dioxide is a volatile compound that does not affect aroma but does influence the body of the coffee.

FrontStreet Coffee Recommendation

Caramelization is most beautifully expressed in a well-judged medium roast. FrontStreet Coffee's Brazil Fazenda Rainha (Queen Estate) is a classic: a yellow Bourbon from the world's largest coffee-producing country, medium roasted to bring out creamed-peanut, chocolate, toast, and sugarcane sweetness - excellent for pour-over, moka pot, or espresso. If you'd like your caramel sweetness with fruit on top, the medium-roasted FrontStreet Strawberry Candy Geisha blend layers Costa Rican honey-processed coffee with Panamanian washed Geisha for orange-blossom honey notes and a rounded sweetness.