In case you haven’t read the original post on the flavor wheel that I posted back in September 2012, you should go read it here. At that time I focused mostly on how turbulence can bring out varying flavors but didn’t spend much time talking about the theory behind it. During the SCAA 2013 Expo in Boston I had the pleasure to meet Mr. Ted Lingle and ask him a bit more about the arrangement of the Flavor Wheel. He did confirm that the arrangement of the flavor wheel is done so according to the mass of the individual flavor or aroma compound. That is to say that as the colors increase in intensity from lightest (Coffee Blossom and Acrid) to darkest (Charred and Creosol) they reflect the molecular weight increase.

The discussion about mass of the compounds is important because, I believe, the flavor development of coffee during extraction is a result of two main components – time and turbulence. The amount of time needed is directly related to the density of the coffee. What I mean by this is that the denser the cellular structure of a coffee particle the more reluctant it will be to give up its flavoring compounds and thus will need more time. Density can be affected by several factors including, but not limited to, origin, processing, and roasting. As for turbulence, we know that it increases the rate of extraction but I theorize this can only happen to a certain threshold. I have expected to over extract coffees from time to time by using turbulence; however, I found that when measured objectively with a refractometer the extraction hadn’t increased but the flavor development had significantly changed.

Let’s step away from coffee for a moment and imagine something completely different. Say you have a pile of three components jumbled together and dumped out on the sidewalk – feathers, wood chips, and bits of broken pottery. There are two ways you can diffuse this pile of things out into the atmosphere of the air. One, you can leave it to time. The gentle breeze and people walking by will cause the feathers to diffuse first out into the atmosphere. The sun, wind, and rain will break down the wood chips and they will diffuse into the environment. And finally, after considerable time the pieces of broken pottery will no longer remain in the pile but will be distributed into the environment. The second way to move these items out into the atmosphere is to introduce an outside force – say a leaf blower. By adjusting the amount of time as well as the amount of force the leaf blower applies to the pile you can change how quickly some of these items diffuse into the atmosphere.

Now I know that’s not a perfect example because there is much more going on during coffee extraction but it is a good starting point. The “atmosphere” in coffee brewing is hot water. On a molecular level as you heat up water you excite the molecules and they begin to move around more rapidly. This closely resembles the wind and people walking by our pile of feathers, wood, and clay. However, in this case the pile is represented inside each individual coffee grind and our items are the three major divisions of flavors on the flavor wheel - sour/enzymatic, sweet/sugar browning, and bitter/dry distillation. The leaf blower can be any number of things that cause outside turbulence including manual stirring, water flowing into the slurry from a kettle or sprayhead, or air bubbles.

In my experience I have found that extraction levels, when measured objectively with a refractometer, have more to do with the overall extraction time. While it is possible to increase the rate of extraction by introducing turbulence I hypothesize that this rate increase only happens up to a certain threshold – meaning that you can only increase the rate so much by introducing turbulence. There are other variables that may increase the rate beyond what turbulence can do (e.g. pressure) but I find that even when a coffee has turbulence applied for the entire extraction period that measured extractions only increase slightly as compared to pulsing turbulence. This is important in understanding how turbulence affects flavor because we have often attributed the flavor development to be a “chance” thing that is related to time and intangible factors. I challenge that you can affect flavor development using turbulence without much shift in extraction because of the fact that flavors have different molecular weights.

All of this theorizing comes from my experience lately in manipulating coffees. One particular coffee that I’ve used recently is the Tairora Cherry Project Papua New Guinea by Counter Culture Coffee. This coffee is unique because it has rather high levels of all three major flavor categories which has made experimentation exciting. Below you can see three different trifecta recipes for the Tairora project. Green is my “Sour / Enzymatic” recipe, brown is the “Sweet Salt / Sugar Browning” recipe, and purple is the “Bitter / Dry Distillation” recipe. When brewed each of these coffees measures around 1.30 – 1.35 TDS and 19-20% extraction yield. However, the flavor development in each cup is significantly different.

The idea that more turbulence allows for more of the heavier mass compounds to be present in the cup means that each recipe has a shift in turbulence. All of the recipes have a 40 second extraction time but with slight increases (two second increments) in Fill Pause Time. The reason I increased fill pause time is that trifecta introduces turbulence during the pre-infusion stage so this is in turn increasing the time for turbulence. From sour to sweet I increased the amount of time of Turbulence On by 4 seconds per cycle (8 seconds total) and I also increased the press out pressure.  The coffee went from exhibiting bright tart cherry characteristics to tasting nutty and sweet with muted acidity. Additionally from the sweet to bitter I decreased the time for turbulence but increased the turbulence power and temperature. With only a slight increase in extraction yield the flavor development changed significantly to become more of a Black Currant Like fruit and a slightly spicy aroma.

Don’t just take my word for it – try it yourself! I recommend starting by using immersion brewing for the experiment since turbulence is easier to control in an immersion brew than in a drip style brew. First, I recommend introducing stirring using a stopwatch at specific intervals while trying to maintain the same force of turbulence. Then brew the same coffee ratio, grind size, total brew time, etc. using either more time or more intervals of turbulence. Finally try it with turbulence the entire time or change up the force at which you apply the turbulence. If you have the ability to measure your extractions definitely do so, but only after you taste. I’d love to hear your feedback as to what you find.

In the hundreds (or possibly thousands?) of brews that I’ve done on trifecta in the past two years I’ve come to taste some distinct differences among the effects of turbulence time, frequency, and force. Trifecta’s unique ability to isolate these variables really sets it apart from other brew methods. By dialing in your turbulence you can really begin to affect not only extraction but also flavor development in your coffees. Beyond flavor development lie other aspects of aroma and body which also are affected by the turbulence applied during extraction. As Nick Cho put it, “turbulence is, in certain ways, a holy-grail of brewing filter coffee.”

Let’s start with a quick review of the flavor wheel and turbulence article that I posted a while back. Remember that flavors develop as a result of time and can be either highlighted or muted by adding in turbulence. The presence of turbulence (or turbulence time) also acts to speed up extraction by ensuring that the water (solvent) around each coffee particle is moving so that it can readily accept coffee flavor (soluble material). Finally, the presence of turbulence helps ensure a more even and thorough extraction throughout the brew slurry.

So time is pretty easy to understand. But now, how about frequency? If you choose immersion style brewing you know that it is almost imperative to have an initial stir or agitation to fully submerge all the ground coffee into the brew slurry. Determining when to repeat agitation can be the tricky part. I tend to default to how dense a coffee is to help me determine how frequently and when to introduce additional turbulence. Low density coffees, whether due to roast or variety, typically need the initial agitation followed by another stir in the middle of the extraction time. Higher density coffees can tolerate three stirs throughout the extraction phase.

Now let’s take a trip down memory lane. A while back I explained how turbulence power works in this post. From that entry here are some highlights:

A coffee that can be more easily extracted does not require intense turbulence while a coffee that is more difficult to extract can withstand higher intensities of agitation. In general, low density and darker roasted coffees need a lower turbulence power and higher density, lighter roasted coffees tolerate higher power.

A forceful turbulence may have the potential to further break apart coffee particles, especially when applied to lower density coffees. Depending on the type of full cup profile you desire this may or may not be a desirable effect. For those who like a much heavier French Press style coffee with plenty of suspended solids this is one way to achieve such a profile. The opposite is true, as well, for those who prefer a lighter {cleaner} cup.

Using a combination of these three variables within turbulence – time, frequency, and force – you can really begin to unlock the nuances of your coffee in a highly replicable format. Play around and let me know your results.

If you were to walk into your local grocery store today it may be hard to find fresh strawberries or corn, because these particular fruits and vegetables are out of season.   Fruits and vegetables have seasonality based on when they are being harvested.   During harvest times or immediately following harvest it’s usually easier to locate fresh produce.    What if I told you the same could be said for coffee?  

Coffee is a seasonal product that has a specific harvest time as well as a shelf life after process.  To learn more about coffee seasonality we went to a couple coffee experts:  Gabe Dunn of Café Imports and Rusty Angell, Field Correspondent for BUNN.

These gentlemen provide some insight into the seasons of coffee!

What makes coffee in season or out of season?

Rusty:  “Coffee’s seasonality is based on harvest time. Harvest times depend upon the region in which the coffee was grown.  After harvest it can take several weeks, sometimes months, before the coffee makes its way to the US and is ready to be roasted. Unroasted, green coffee can be stored for approximately one year under normal conditions.”

To see when coffee is being harvested in various regions of the world see the Seasons Chart form Café Imports  CLICK HERE

Is there an “off season” for coffee?

Gabe: “I'd like to clarify the difference between "out of season" and "past-crop," as I feel they are often confused. Generally, a coffee is considered in season if it has been harvested within the last 6 months. A coffee is past-crop when it has been a full year since its harvest. Worth noting is that neither automatically mean a coffee is bad.”

 If a person doesn't have a seasons chart is there a way to tell if a coffee is "in season" just by looking at it? 

 Gabe: “Short answer: Not really. Without knowing the respective growing seasons of all coffees by heart, the easiest way to tell if a coffee is out of season/past-crop is by tasting it. As a coffee gets older, it's more likely to exhibit certain characteristics associated with age, such as papery, grassy, stale, etc. As organic plant matter, all coffee is subject to cellulose decay, thus causing these flavors. “

 Is there a particular time of the year when coffee is more scare/harder to find?

Gabe: “If you are looking for a very specific coffee, there will always be a time of year that you are less likely to find it.  This is usually just before its fresh crop. While November and December are low-season for some coffees, it’s also when we see fresh crops from other countries, such as Ecuador, Brazil, and Burundi.” 

How do café’s manage their assortment given the harvest schedule?

Rusty: “Some cafes have seasonal offerings. However the act of blending coffees together (a very common practice that is only recently beginning to decline) was meant to make up for the seasonality of coffee. By blending coffees together you can find in-season beans with similar attributes to create a blend that tastes mostly the same throughout the year.”

What can a person do if they love a particular coffee, but know it is only in season for a short time?

Gabe: “My recommendation is to enjoy your favorite coffee while you can and maintain a diverse palate! Delicious coffee is as abundant as it is fleeting. Even a coffee from a specific producer can change year to year, so it is best to not get overly attached.” 

Rusty:  “Enjoy it while it lasts! Like any good wine, coffee can vary from year to year as growing conditions fluctuate.”

Last year I posted a few of my favorite things from my first year of being a barista with trifecta. This year I have to say those things are still way up on my list but I've got a few more to add in 2012.

This year I've learned a thing or two about what to bring when I either visit an existing customer or go to a new install. There are couple essential tools that I've added to my favorites list:

1. An assortment of John Guest Speedfit® fittings. I love quick connect fittings because they are secure and, well, quick! They’re perfect for short term show set-ups as well as long term bar installations. I most often use the 1/4" female flare to 3/8" tubing

2. A place to keep all my little connections and fittings and the tools to hook them up - Plano 23630-01 Deep Stowaway with Adjustable Dividers. This little kit travels with me everywhere. I keep fittings, tools, and trifecta software programmers in it. I’ll admit, it is almost too small, but its size is just right for my mobile lifestyle.

And the third is something that I use in teaching and have found myself giving away often times since folks like them so much.

3. Electrifying markers for charting trifecta recipes. Expo Bright Sticks Wet-erase markers. These work on any non porous surface (glass, metal, plastic, laminated paper, and more). They’re great for use during trainings to not only mark the recipe lines but also to take notes and illustrate brewing concepts.