Phase-rs Set on Stunning!

I’m tired and my brain isn’t functioning well, so that’s the title that came to mind when talking about the phases of roasting. Sorry, cheesy I know.

So last post I shared with you the various roast levels for coffee, their common names, and the temperatures the beans need to reach to achieve those roasts. But as you could probably guess, beans don’t go from green to roasted in a flash - there are phases the beans go through in the process of roasting to achieve what I call coffee nirvana. Stunning indeed!

The Stages of Roasting

This is a simplified but fairly accurate depiction of the phases a coffee bean goes through in the process of roasting.

Let’s do a bit of preliminary defining so that the terms all make sense when we use them. Here are some of the main terms in the coffee roasting process:

Drying - the process of extracting moisture from the coffee bean.

Maillard reaction - the process of browning, in which the sugars inherent in the coffee bean start to caramelize and darken.

Hay Phase - the first phase of browning characterized by the slight yellowing/tanning of the beans.

Cinnamon/Bread Phase - the second phase of browning characterized by the transition from yellow/tan to the color of cinnamon.

First Crack - the point at which the bean ruptures because of the build up of pressure caused by the vaporization of the moisture in the bean.

Development Phase - the phase between first crack and second crack during which many of the flavor compounds are developed in the bean.

Second Crack - the phase where the additional moisture in the bean causes the bean to rupture even further.

Drop/End Roast - the end of the roasting cycle where the beans are dropped from the roasting element into the cooling bed.

Roasting Profile - at the end of the roast, the graphic representation of all phases of the roast through the observation of bean temperature, drum temperature, time and the addition or subtraction of gas and airflow.

One of the important elements present in a coffee bean is moisture. In fact, it is so important that the ICO (International Coffee Organization) states that beans received for roasting must be between 9-12% moisture. Any drier and the beans lose their flavenoids. Any wetter and the beans can mold or start to ferment and that is not yummy!

So we have the beans and they’re about 9.5% moisture. So what now. We will inspect the beans to ensure there are no defects (more on bean defects in a later post). When that’s done and the defects are removed, we at SweetBeans pass our beans through a machine called a destoner. And that’s exactly what it does - remove stones (and other non-bean things) from the beans. Our destoner has a hopper where the beans are placed. Then it’s turned on and a precisely tuned vacuum sucks the beans through a chute and deposits them into another hopper. Because of the precision of the vacuum, anything heavier than a bean (like a stone) falls into a small tray at the bottom. So why take this extra step that some roasters deem unnecessary? Well, have you ever run beans through your grinder only to have a stone hit the grinding plates? You’ve just destroyed your grinder. And we don’t want our customers or our cafe destroying their grinders!

With the destoning done, we turn to the roaster. While we were destoning, the roaster was gently heating up to a nice 390 degrees through the use of gas/heat and air flow. Once that heat plateaus and remains steady, the beans are loaded into a hopper at the top of the roaster. Once the roaster temperature hits the desired temperature, the beans are released from the hopper into the roasters drum. Immediately the temperature of the drum and air drop because you’ve just introduced a mass of beans whose temperature is considerably less than the inside of the roaster. Then we wait, looking for the point where the heat of the drum and the heat of the beans reach equilibrium. That point is called the “turning point”. It’s called that because, in graphing the roast, it is the point where the graph no longer declines and instead “turns” toward rising.

Now, the process starts where the only control the roaster has over the beans is the increase or decrease of gas/heat and airflow. The roaster wants to achieve a steady rate of rise - the degrees of change in temperature of the beans over a 1 minute period. In other words, if the beans were at 310 degrees at 4 minutes, and they were at 350 at 5 minutes, then the rate of rise is 40. The rate of rise is very important because it both prevents defects such as scorching and allows for a greater development of flavor. Coffee guru Scott Rao says “a great roast is achieved with a continuously decreasing rate of rise (RoR) over the time of the roast.” In other words, the more you slow down your rate of rise over the time the coffee is roasting the more complex and delicious your coffee will be. Because of the technology involved in our roaster here at SweetBeans, it is easy for us to track and know our RoR at each moment of the roast. For others with a less technologically advanced roaster, it might require a timer, thermocouple and a pad of paper and calculator.

Now I will say this about my roasting method - I kill the gas just prior to dropping the beans in the drum. Why, you might ask? Because data has showed that a drum that is hot as hell can cause beans that come in contact with it to scorch and blow out the wall of the bean (called tipping), thus causing a flavor-changing defect. So I kill the heat just before dropping as a means to prevent that. Now, with the beans in the drum, I’ll wait a hot second before applying more heat and some air flow. As the drop in temperature starts to slow, I’ll turn on a bit of gas to start the process of raising the temperature because there is one thing that is deadly to coffee and that is the dreaded STALL! A stall is when your rate of rise either becomes zero (0) or actually declines and everything starts to cool. This is dangerous because it can produce a coffee that tastes baked and musty. Not yummy!

So we add some heat as the beans enter the first phase of the process called “drying”. This phase results in exactly that - the beans begin to dry and lose some of their greenness and moisture. But it’s just as much about the moisture in the bean beginning to turn to vapor and pressurize the bean. There is a key factor in this phase - too fast of a drying phase will result in the next phase also being too too fast which will result in thin, flavorless, bodiless coffee that just doesn’t have much going for it. The plan is to ensure the phase proceeds forward without pushing it too fast into the next phase, the Maillard phase.

The Maillard reaction occurs in most foods to which heat is applied. It is the transformation of carbohydrates (sugars) and amino acids into flavor compounds that in the end result in the coffee beans taking on its “coffeeness”. Think about a steak. You season it and place it in a hot cast iron skillet. Immediately the heat of the skillet begins to transform the proteins in the steak into something “ultra-steaky”. The resulting crust of the steak holds the best imaginable flavor of steakiness. Now take another steak and boil it. What does it taste like? Flavorless wet meat. No flavor compounds have developed because the Maillard process was not allowed to occur. The same goes for coffee beans. What if we took coffee beans and boiled them to 445 degrees, the temperature for a dark roast. Let’s grind those and taste the coffee. No flavor, disgusting, akin to the water in a bathtub. Now take coffee beans and roast them over indirect heat, allowing them to brown and develop the caramelized sugars of the Maillard reaction. Done right and you’ve produced a cup of heaven!

Once we enter the Maillard phase there are two checkpoints the coffee will go through before reaching first crack. First, the beans go through what is called “hay phase” - the beans turn slightly more yellowish tan and the aroma of the beans changes markedly from green and vegetal to more of a dried hay aroma. At this point the beans still don’t have the smell we associate with coffee, but they don’t have the smell we associate with green beans either. At this point we’re starting to see a color-shift in the bean along with a transformation of the sugars in the coffee. Between this phase and the next phase, sucrose is transformed into acetic acids, many of which can be sour. You would never stop a roast here because the coffee would be inedible. But this phase is very important to the final aromas and flavors of the coffee. Once the roast moves past 365 F, it starts to achieve a slightly darker color and the beans turn somewhat red-tan - we have entered the “cinnamon/bread phase”. In this phase the beans take on the color of cinnamon, and the aroma of baked bread. The caramelization process continues past this phase as we approach a very important milestone - first crack.

We’ll pick up next time with first crack, and continue through the end of roast, finally achieving coffee nirvana!

Until next time BeanHeads,

It’s always a beautiful day at SweetBeans! Cheers!

James