Maillard Reaction in Coffee Roasting

20160428

Maillard Reaction is a type of browning, producing a variety of aromas and flavors in addition to dark colors.

Browning is categorized into Enzymatic Browning and Non-enzymatic Browning. Enzymatic browning is a chemical process. Requiring exposure to oxygen, enzymatic browning gets polyphenol oxidase, catechol oxidase and other enzymes interacted with oxygen. It develops melanins and benzoquinone from natural phenols, leading to a brown color. Enzymatic browning can be beneficial for developing flavor in tea and developing color and flavor in dried fruit such as figs and raisins. However, it can be harmful to fresh fruit, vegetables and sea food such as apples, bananas and shrimp.

Non-enzymatic browning contains Maillard Reaction and Caramelization. Non-enzymatic is also a chemical process, but different from enzymatic browning, non-enzymatic browning develops brown colors without the activity of enzymes.

Caramelization is the pyrolysis of sugars, resulting in caramel flavors and brown colors. We could discuss the topic of Caramelization in our next reviews.

Let’s talk about Maillard Reaction. Named after French chemist Louis Camille Maillard who first described it in 1912, Maillard reaction is a chemical reaction between amino acids and reducing sugars, developing desirable aromas, flavors and darker colors. The reaction proceeds rapidly from around 140 to 165°C. Along with higher temperatures, caramelization becomes more significant. The reactive carbonyl group of sugars reacts with the nucleophilic amino group of amino acids of proteins, resulting in a variety of aromas and flavors in addition to dark colors. This process is speeded up in an alkaline condition. The type of the amino acid determines the resulting flavor.

In the process, hundreds of different flavor compounds are created. These compounds, in turn, break down to develop more flavor compounds, and so on. Now that we know Maillard reaction is significant between 140°C and 165°C, how should we deal with the gas pressure and airflow of our coffee roaster during this temperature range?

(To be continued!)