Coffee Roasting Part One: The Basics To Roasting
There really isn't that much to it.
Keep roasts around 10 to 15 minutes.
The roast is made up of three phases that need roughly equal time segments. Charge to Dry End (dry end) o o dry end to First Crack (first crack) first crack to End of Roast (end of roast) o This phase is called development time (development time) At least a minute more on development dev elopment time for espresso roasts than for brewing is needed. And longer than that if the espresso is light. □ - The lighter the espresso roast, the longer development time is needed. These phases can be achieved on almost any roaster that gives some control and o the roaster is willing to roast in small batches and watch c arefully.
To Profiles
Basics to Understand how to Profile Understand The Roaster o Heat application and its transfer to the beans Temperature adjustments Air flow adjustments Roast monitoring capabilities Visual, smells, sounds, Temperature (BT,ET,MET) □ Identify and work with or around shortcomings Understand the beans o What will cause different beans to roast and taste differently Bean density and size □ Moisture content □ Processing □ - Wet processed, various dry processed, decaf Identifying and culling defects pre and post roast □ Understand roasting chemistry and reactions o Determine when reaction happened at different times of a roast, and how they affect taste.
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Plan a Profile A profile must incorporate all parts mentioned above. Break down the roast profile into phases. Determine a roast level.
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The Roast Use the profile Monitor the roast Collect data Adjusting on the fly, if possible, to stay within the profile Determine if any changes are needed to nail the profile better next time Taste the results and change the profile if needed
To Chemistry
Three Basic Things Happen While Coffee is Roasting The Three Stages 1) Water evaporates o o 2) Organic acids and aromatics break down or are boiled off 3) Water, sugars, and amino acids combine in a chain of chemical reactions o collectively called the Maillard reaction. 1) Water Evaporating This happens from the moment the beans are heated up to the first crack. o At first crack the remaining free water escapes. Below 150C bean temperature, not much is happening except water o evaporating. As the beans exceed 150C, a steam wave moves out of the bean from its center. o This wave also starts the Millard reactions. o If the bean is too moist going above abov e this, the bitter organic acids will not break down as quickly. If too much water evaporates, the Millard reactions are starved, and the roast o will be dominated by dry distillates The charge temperatures, or early bean heating should be adjusted to achieve o this balance in 300 - 530.
2) Organic Acids and Aromatics Breaking Down or Boiling Off o Roasts have to go to partway partwa y into the first crack since this is where the chlorogenic acids that make unroasted coffee intensely bitter finish their breakdown. o The smaller acid molecules and aromatics, which are responsible for the fruity aromas and acidic tastes start breaking down around here. The longer the beans stay at temperatures above about 199C the lower the o acidity will be.
For instance, stalling the beans around first crack will reduce acidity without reaching temperatures that caramelize off the sugars. □ Too much of this is a roasting flaw called bak ing, which overly flattens the flavor of the coffee.
3) Millard Reaction Chains This is where the complexity of coffee is created, since these reaction chains are o hugely complicated. There are some overall guidelines. o The early Millard reaction, from dry end (150C) to around first crack (199C), creates nutty, toasty, and woody flavors. At higher temperatures, sugars stop reacting with amino acids and start caramelizing on their own, creating caramel, vanilla and chocolate flavors. Finally, also at higher temperatures, and when th e water required for early Millard reactions and caramelization runs low, the Strecker degradation changes the compounds created earlier ea rlier in the roast to dry distillates smoky, spicy and peaty flavors. The simplest lesson here is that these processes compete for water. Taking a longer ramp to first crack and less time thereafter will favor the woody, toasty, nutty flavors and reduce the caramel ones. Go as fast as possible earlier in the roast and the Strecker degradation creating these flavors is controlled. If the roast is to get very dark, the only way to avoid overwhelming distillate flavors is to dry the beans less.
Coffee roasting reactions (Millard) have autocatalytic cycles, but aren't self-organizing. A bean is a closed system and eventually runs out of amino acids, sugars and o water (the basic reaction foods).
