Why Does Your Coffee Taste And Smell Delicious?

The major difference between coffee roasts come from the chemical reactions that occur in the coffee beans at certain temperatures. As a result of these chemical reactions, aromatics, acids and other flavor components are created, balanced or altered in a way to build the perfect flavor, acidity, after taste and body of coffee.

1. Maillard Reaction 
A key reaction for the development of roasted coffee flavor and color is the Maillard reaction. At temperatures from 150-200 degrees Celsius,  carbonyl groups (from sugars) and amino groups in protein react to form aroma and flavor compounds. Hundreds of coffee flavor compounds are formed from Maillard chemistry, including potent coffee aroma flavor component, 2-furfurylrhiol.

Flavor Compounds Include:

  • The roasted flavor in coffee comes from 2-furfurylrhiol and
  • Trigonelline gives coffee that bitter taste

2. Caramelization
From 170-200 degrees Celsius, the sugar in coffee start caramelizing which browns the sugar and releases aromatic and acidic compounds during roasting, most of the sucrose is converted to caromelized compounds, but if you roast the coffee too lightly, the bitter tasting compounds won’t degrade

Caramelized Compounds Include

  • Diocetyl gives coffee a buttery or butterscotch flavor and
  • Furonones have a burnt sugar flavor

3. First Crack
Around 205 degree Celsius, water inside the bean vaporizes, causing the bean to expand and crack (both physically and audibly). This first crack makes the bean double in size. Prior to first crack, the bean changes from a green/yellow color to a light brown color. At this point, the bean loses about 5% of its weight from water loss

4. Pyrolysis
At approximately 220 degrees Celsius, the heat causes a chemical change inside the beans, leading to the release of carbon dioxide. This process is called pyrolysis. The color changes to a medium brown and the bean losses 13% of its weight. Light roasts are done after this step
Acetaldehyde is produce during pyrolysis and has a green apple aroma

5. Second Crack
Pyrolysis continues as temperature reach 225-230 degrees Celsius, causing the second crack in the bean, That second crack in the cellulose in the cell wall of the bean breaking apart. The bean is now medium -dark brown in color and has an oily sheen. It’s during this step where the aromatic compunds are releases, contributing to coffee’s classic flavor.

Aromatic Compounds Include:

  • 2-isobutyl-3-methoxypyrozine gives coffee an earthly scent and
  • 2-ethyl-3,5-dimenthylpyrozine odds earthly, roosted notes

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