Coffee Roasting | Chemical Reactions

1. Maillard Reaction

• The Maillard reaction is a chemical reaction between amino acids and reducing sugars that gives browned foods their distinctive flavor. This reaction begins at lower roasting temperatures and continues to develop throughout the roasting process.

• At lower temperatures, the Maillard reaction is less intense, preserving more of the original sugars in the coffee bean. This leads to a sweeter flavor profile.

• As the temperature increases, the Maillard reaction becomes more pronounced, producing a range of flavor compounds that contribute to the complexity of the coffee. These compounds include various types of melanoidins, which are responsible for the brown color and rich flavor of roasted coffee.

2. Caramelization

• Caramelization is the pyrolytic process that involves the thermal decomposition of sugars at high temperatures, leading to the formation of caramel-like flavors. This process typically occurs at temperatures between 170°C to 200°C (338°F to 392°F).

• At lower end temperatures, caramelization is minimal, preserving more simple sugars and resulting in a sweeter coffee.

• At higher end temperatures, caramelization is more extensive, creating a range of caramel flavors and contributing to the complexity and richness of the coffee. The process also generates bitter compounds that help balance the sweetness.

3. Strecker Degradation

• This reaction is part of the Maillard reaction pathway and involves the degradation of amino acids by reducing sugars, leading to the formation of aldehydes and ketones. These compounds are essential for developing the aroma and flavor of coffee.

• Strecker degradation intensifies with higher roasting temperatures, producing more varied and complex aromatic compounds.

4. Pyrolysis

• Pyrolysis is the thermal decomposition of organic material in the absence of oxygen, occurring at high temperatures during coffee roasting. This process breaks down larger molecules into smaller ones, contributing to the development of volatile compounds that influence the aroma and flavor of the coffee.

• Higher end temperatures enhance pyrolysis, leading to the formation of diverse aromatic compounds and bitter notes that complement the overall flavor profile.

***** Coffee roasting involves key chemical reactions that shape its flavor and aroma. The Maillard reaction and caramelization develop complex flavors and sweetness, with the intensity varying by temperature. Strecker degradation and pyrolysis further enhance the aromatic profile and bitterness, especially at higher roasting temperatures. Understanding these reactions helps roasters control the flavor profile of the coffee.

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