Coffee Roasting | What is Roasting? What Chemical Reactions Occur During Roasting?

FrontStreet Coffee on Coffee Roasting

Coffee bean roasting means heating raw beans to drive a series of physical and chemical reactions inside and outside the bean. During the roast, the beans expand to about one-third larger than they were raw.

The fire under the roaster releases coffee's aroma and draws out each bean's character — acidity, sweetness, and bitterness — in full. What starts as a bland raw bean becomes the mellow fragrance in the cup that lingers long after the last sip.

Roasting is the most important stop on the long journey of every coffee bean. It is where character is outlined and aroma is nurtured.

The process is a lot like popcorn: full of fragrance and pleasant popping. From raw beans through light, medium, and dark roasts, moisture is released again and again. Weight drops, but volume slowly swells. The beans darken, aromatic oils are gradually released, and the texture turns crisp.

Raw beans hold large amounts of chlorogenic acid, which gradually disappears during roasting and releases the familiar, pleasant fruit acids — acetic acid, citric acid, and malic acid, the same acids found in wine. A well-judged roast brings these acids forward in just the right way, while over-roasting masks them completely.

FrontStreet Coffee Recommendation

A medium roast is the level that keeps acidity, sweetness, and bitterness in balance, and two FrontStreet beans show what that means in the cup. FrontStreet Brazil Queen's Estate is a yellow Bourbon from Brazil — clean and gently sweet, medium-roasted into creamy peanut, chocolate, toast, and sugarcane aroma, and just as comfortable in a pour-over as in a moka pot or espresso machine. FrontStreet Jamaica Blue Mountain No.1, a Typica, is also roasted medium; that level is what lets its acidity, bitterness, sweetness, and body fuse into one elegant whole, with chocolate, toasted nuts, cream, and caramel coming through from the first sip. Both are good reminders that roast level, not just origin, decides how much of a bean's character reaches the cup.