Roast Approach: Roast Strategy

As I've been publishing these "Roast Approach" blogs, I thought it could also be helpful for readers to understand my methodology behind how I approach roasting these coffees.  Every roaster likely has a different method, based on how they were taught roasting and their continuing roasting education.  I started my roasting career a decade ago, sample roasting on a cast iron 4-barrel Jabez-Burns sample roaster.  The breadth of my initial training included a pixelated image of what the flame should look like and 15 minute primer on how to work the roaster (and not start a fire).  When I started roasting, I used only a pen, paper, and timer.  I had no thermocouples, no temperature gauges, no Cropster.  What I did have at my disposal was ample green coffee from a multitude of origins, a moisture reader, an Agtron, and plenty of time to cup.  I learned coffee roasting from the coffee itself.  Over the years I've held many other roasting positions, roasted on a multitude of machines, and had the opportunity to learn from some of the best roasters in the world.  One thing I am certain of is that there is no one "right way" to approach roasting coffee.  I have had amazing coffee from roasters who used a simple pen and paper, as well as amazing coffee from roasters that had all the latest technology at their disposal.  But just as I have been greatly influenced in my roasting strategy from conversations with other roasters, I feel there is likely some value in sharing my own roasting philosophy.  

Overall, my approach to roasting is to think about what chemical changes and reactions are happening at different phases during the roast.  With this in mind, I break the roast down into 4 phases: drying, Maillard, caramelization, and post crack development.  I use temperatures as mile markers in my roasting, so it should be noted that temperatures readings are always relative to one's own thermocouple set up.  What is 305 on my roaster, may not be 305 on yours.  In that regard, take the numbers with a grain of salt.  It's probably worth noting at this point my feelings towards "first crack".  While first crack provides an audible marker, very important to the sensory roasting process, there are no particularly important chemical reactions that are happening at that moment.  Development of flavors starts all the way back at around 305 degrees Fahrenheit, when Maillard has started.  Caramelization of sugars, which are closely linked to what many roasters consider "development" of coffee starts all the way back around 320-350 degrees.  By the time first crack happens, the coffee is already deep in the throws of development.  For that reason, I refer to development after first crack as "Post Crack Development".  I recognize that it is an important marker, but by no means should we wait to start paying attention to our coffee until first crack happens.  Additionally, through experimentation, I have found that with alternatively processed coffees the point at which first crack happens can be greatly impacted by the heat application earlier in the roast.  That's a rabbit hole to venture down on another day, but it gives more credence to my theory that first crack isn't all it's cracked up to be.  (Pun Intended)

Phases Of The Roast

Drying - The first phase of the roast is the drying or evaporation phase.  Prior to entering the roaster, the processed green coffee is somewhere between 12-9% moisture.  In order for the Maillard phase to begin, the coffee must get down to between 6-7% moisture.  Once the coffee enters the roaster, the coffee begins absorbing heat and the moisture evaporates on the surface of the seed.  Internally, water molecules try to preserve themselves by consolidating in the center of the seed.  This bit of moisture in the center will be critical to the audible "pop" experienced at first crack.

Maillard- Maillard is the non-enzymatic browning, whereby heat (rather than an enzyme) is the catalyst for the change.  These chemical reactions require a low moisture (6-7%) and typically begin happening around 305 degrees Fahrenheit.  It should be noted that Maillard includes a whole series of chemical reactions.  For the purposes of my roasting strategy, I'm looking at the early Maillard stage when I use the term "Maillard Phase".  During this phase, sugars and acids are reduced and recomposed into volatile and non-volatile reaction products.  The big take away here is that this is where many of the aromatics are formed and noticeable visual color change is taking place.  Moving quickly through this stage of Maillard will produce more acidity and sweetness, while more time (slower) spent in this phase will produce more rounded acidity, full sweetness and heavier body.

Caramelization - This phase begins between 320-356 degrees Fahrenheit, with different sugars breaking down at different temperatures.  Non-enzymatic browning at this point contributes to more color, aroma and flavor.  This is where melanoidins begin to be produced.  Melanoidins are heavy compounds in coffee formed from a combination of polysaccharides, proteins, and chlorogenic acids. They have a "bready", biscuit, or pastry-like character and contribute to the body and mouthfeel of the coffee.  During caramelization, simple sugars like sucrose break into even simpler sugars such as fructose and glucose.  Too little time in caramelization can cause a coffee to lack aromatics and body.  Too much time in caramelization can break down acids that contribute to fruit-like cupping notes. Another important action happening during this phase is acids are breaking down.  Citric acid begins to decrease at 350 degrees and malic acid around 375.  During the duration of a roast, quinic acid (attributed to a bitter character) doubles as other acids break down.

Post Crack Development - As coffee is roasting, the small bit of moisture that has centralized inside the seed develops steam pressure.  At this point, the coffee seed still has a great deal of pliability to it's structure.  When first crack occurs, the seed splits open slightly to release the steam pressure, then closes back up.  In coffees that have undergone alternative processing methods, such as honey processing or anaerobic processing, the seed may have a softer and more pliable structure.  Due to this pliability, the coffee may take longer to build up the steam pressure that would force a first crack.  Additionally, first crack may be very soft and quiet.  Anecdotally, I have found that intense heat during Maillard can make the seed slightly more brittle going in to first crack, creating an earlier and more noticeable cracking sound.  It is important to remember that regardless of what temperature first crack happens at, development of sugars and breakdown of acids is already in full swing.  A coffee with a late first crack (such as a honey processed coffee) may only need a small amount of post crack development to reach the intended point of acid and sugar balance.  

Building a Roast Approach: Setting Goals

When I set out to approach a coffee, I start by thinking about what I want to achieve as my final product.  If I have cupped a sample roast, I may be looking to mimic the tasting notes I found in the sample.  Or, I may be looking for a particular utility of roast, such as roasting for drip or espresso.  Once I know what I would like out of the coffee, I work backwards to design a roast profile that I think will get me there.  

I consider which phases I might want to stretch out or shorten during the roast to achieve my goal.  For high acidity and bright fruit notes, I think about a short and fast roast where Maillard, caramelization and post crack development are all rather short in duration.  For a round, sweet, fruit forward cup I would be thinking about a short Maillard, a longer caramelization, and a fairly short post crack development time.  When considering the utility of a coffee, I may look to mute out or reduce acids by extending time in caramelization and post crack development.  

Below is a diagram to give you an idea of what's going during a roast.  

Below is a diagram that helps to show (albeit roughly) how chemical changes during the roast correlate to common roast levels.

I use this concept of roast development as I am deciding what kind of final product I want to end up with.

Building A Roast Approach: Writing A Roast Plan

My first step in starting a roast approach is to fill out my roast plan.  In this plan I am looking at making intentional and purposeful modifications for each roast phase.  As heat changes in a roaster do not happen immediately, I typically plan my modifications 10-20 degrees before the phase begins.  For instance, in order to have a short Maillard phase, I need to have an aggressive heat application when Maillard is beginning at around 300 degrees.  For that, I make my increase in gas at 280 degrees. In a roaster that uses more convective heat and is more reactive to gas changes, I may make those changes closer to 300.  In a roaster that is uses more conductive heat and is less reactive, I may make those changes closer to 260.  

Here is a sample of the roast plan that I use:

I start with some notes added in.  These are generally the same for each of my roasts.  If I find that a roast needs modifications (such as for addressing a crash or take off) I will cross out what is filled in and write my new number in.  

Here is a sample of a filled out roast plan.  The areas that I have filled in with blue are filled in prior to beginning my roast.  Areas filled in with green are typically filled in during the roasting time itself.  I also utilize Cropster while roasting, but find that having a clear plan going in to the roast provides much more context about how the coffee is responding and allows me to make more meaningful modifications as I seek to achieve my goal.

As I cup my final roasts and think about changes I would like to make to the roast, I go back to this model.  Do I want more acidity?  Shorten Maillard by punching it with intense heat.  Do I want a rounder more pronounced sweetness? Reduce my heat in caramelization and extend time in this period.  

In Summary

Coffee is a unique agricultural product.  Each decision made in the growth and processing of the coffee, from which variety is selected for cultivation to the way in which it was processed, impacts how the coffee will react through the roasting process.  There will always be coffees that buck every trend and common approach.  Additionally, coffee will continue to change chemically as it ages.  For myself, I have found that taking a methodical approach to each roast allows me to best observe the coffee and understand the "why" of what's happening in the roaster.

If you have thoughts or comments about this approach, such as how it may be similar or differ from your own approach to roasting, let me know.  I'm always happy to continue my roasting education by learning from my peers. 

Happy Roasting!

-Emily