Into the Light

This is part 3 of a 4-part series from our Roastmaster, Paul Allen.  Parts 1 and 2 can be found here and here.

Last month, in Part 2 of our series, we looked at some definitions and delved into the light roasting profile, its flavor and what some of the chemicals were doing during the process. Now, we move attention to the medium and dark roasts and think about their profiles. Again we are not so concerned about whether we like a given profile but with recognizing what it tastes and looks like.

Michael McIntyre, a coffee professional and fellow Q Grader, says, “Coffee’s dynamic history is a small testament to its full spectrum of enjoyment. That dynamic is experienced in a roaster’s interpretation through roast development. The roaster has a unique opportunity, nay obligation, to study a coffee’s performance potential under the microscope of taste and present that coffee to the world the way that he or she feels it is best represented, or dare I say, preferred.” This is why we practice different roasts for different coffees and clients.

Medium Roast

wheel_bigThe medium roast develops past the light roast as time and temperature rise and keep ticking. This is when the Maillard reaction kicks in, creating flavor and browning the beans, with huge implications in what we taste in the cup. We see and taste the Maillard reaction in the browning of bread into toast, the colors of beer, chocolate, coffee, and maple syrup, and the flavor of roast meat.

Some suggest this reaction optimizes at medium roast. Once again from my experience, we can’t reduce flavor attributes to a single roast level for every coffee. At this level, the flavors nutty and chocolate are often found–but not always.

At medium roast we begin to add body, decrease acidity and see a slight drop in origin distinction. This is where you’ll find a good balance of bitterness, acidity and fullness. Organic acids are changing in strength: Citric acid is now only 50% of its original concentration, meaning that it is losing more of that lemon/orange taste. Acetic acid (e.g. vinegar) is at its peak. At low concentrations, acetic acid imparts a pleasant clean, sweet-seeming characteristic, but at higher concentrations, as in a medium roast, it can have some fermented characteristics. Quinic acids (e.g. found in tonic water) are increasing also, bringing some bitterness and astringency.

Dark Roast

By the time you hit dark roast, the Maillard Reaction is in full swing. We find sweetness in the cup, which is of course desirable, but there are diminishing returns as starch and cellulose also carbonize. Chlorogenic acid (CQA) has split into quinic acid (often experienced from coffee brewed too long on the burner) and caffeic acid, a good antioxidant yet both bitter and astringent. The caffeic acid in coffee is often responsible for the bitterness we associate with coffee. Quinic acid, on the other hand, is the actual primary cause of coffee’s acidity and astringency.

At this roast level, the coffee will begin to lose brightness as well as gain some bitterness and a fuller body. A dark roast tends to have flavor notes that can, but not always, rely more on the roasting itself than the unique character of the bean (such as smokiness). At this stage bean quality becomes less discernible, like comparing overcooked fine sirloin or ground beef; even a culinary expert might not be able to tell the difference.

Next month we will start drawing some conclusions from these profiles we’ve been exploring.

 

2 thoughts on “How Much Do You Know about Coffee Roasting? Part 3

  1. Steve says:

    Hi Paul.

    I’ve started doing cold brew coffee at home and enjoying trying different beans and roasts. Interested to read where the chlorogenic acid split occurs. and that the quinic acid contributes to acidity in heat and pressure brewed coffee. Going back to read parts 1 and 2.

    Thanks

    • Paul says:

      Glad to have contributed. I have another couple of parts coming with some conclusions, I haven’t tried it with cold brew so much but the chemistry will be similar in the roasting aspect

Leave a Reply

Your email address will not be published. Required fields are marked *