INTRODUCTION

Every year in late winter and early spring, all US Roasters face a “time” where there are few freshly harvested coffees to refill their stocks. It is a waiting game familiar to everyone in the industry. During this time, many Roasters may wonder, “Did I buy enough coffee to get me through to next harvest?” We talk with our trader partners and producer friends to see when we can expect coffee to arrive and then secure just enough inventory to see us through. If we buy too much, we will be roasting and selling dreaded “past crop” coffee while we enviously watch our friends and competitors joyously celebrate all of their delicious “new crop” coffees. If we buy too little, then we rally to our importer friends and see what coffees they may have left on their spot lists. The selection may be sparse, but often times you can get a great price on a coffee that will get you through as a stopgap until fresh coffee arrives. Being on top of your inventory game is one of the best tools in a Roaster’s toolkit.

Past crop is a dirty word that gets thrown around a lot in the specialty coffee industry but the heart of the issue is that all coffees age on the shelf. Some coffees age quicker than others and several people in the industry are working hard to find ways to increase the shelf life of coffee. My colleague, Chris Kornman, recently published an article on using water activity as an indicator of the stability of green coffee called Green Coffee Analytics: Relevance to Roasters, Buyers, and Producers – Part I: Moisture Content and Total Water Activity. Lab equipment can be very useful in helping green buyers decide whether or not to buy large amounts of a particular lot of coffee.

After we purchase coffee, our own storage environments can also accelerate the shelf life and prematurely age our supplies. Mitigating humidity and maintaining a steady temperature in your warehouse is crucial if you want to protect the life span of your coffee. The ideal relative humidity is 60% with an average temperature of 75 ° F. Investing in a digital humidity and temperature monitor for your warehouse is relatively inexpensive and can help you suss out whether you need to take further action.

So what does age taste like in coffee? There are several answers and all of them have negative implications. As coffees age, their volatile acids decline and become less present. On the cupping table this is often described as faded or muted fruit flavors. The sweetness of the green coffee quality also declines. This decline leaves a sour taste, often described as cellulose (plant fiber) or paper. The descriptor “baggy” is used often, but may not always be an indicator of age. Coffee that tastes like the jute bag it was housed in, may have also experienced water damage in transport, thus possibly creating the jute taint. Increasingly, roasters and importers alike have requested that coffees are stored and transported with protective liners like GrainPro and Ecotact to eliminate the occurrence of “bagginess” in coffee. Bourbon Specialty Coffees, an exporter in Brazil, has researched and developed a new bag that will solve the issue of jute contamination and perhaps increase the shelf life of their green coffees.

THE EXPERIMENT

No roaster is impervious to dealing with coffee that has started to decline in flavor. Many roasters have developed techniques to deal coffees that have passed their prime. The Crown Team at Royal Coffee would like to take a closer look at these aging green coffees and see what can be done about them. As a roaster, I will take the first crack at this.

Below, I’ve attempted a number of roasting techniques that have helped me mask the flavor of age in the past. I roasted 33765 – Guatemala Huehuetenango Jacaltenango for this exercise, a coffee which arrived in our warehouse in May of 2015.

PR-1024: THE CONTROL ROAST

My first roast of the 33765 – Guatemala Huehuetenango Jacaltenango, PR-0124 (white), was my standard Central American profile. I dropped the batch at a temperature that was a nice light medium. In the cup, this coffee maintained a lot of fruit acids including; grape, orange, and green apple. However, this coffee finished sour and papery.  For a green coffee that has sat in our warehouse for almost a year, it was aging better than I had expected. While the taste of age was unmistakable, several positive and delightful volatile acids remained.

Since the acids were still readily present, I wanted to see what I could do that would increase sugar browning and eliminate only the dry papery flavor. The first and most obvious technique is to roast the coffee darker.  Both PR-0141 (red) and PR-0142 (gray) are roasted to a higher end temperature (+5-6°F). I could have taken it further, but I still wanted to preserve as many of the fruit acids that remained in the coffee.

PR-1041: ROAST DARKER AND REDUCE AIRFLOW

Reducing the amount of airflow and increasing moisture in the drum is a technique that I have used with other roasting machines in the past. Our Probatino posed a few challenges when hoping to employ this method. The sole airflow baffle on the machine is located on the stack from the drum exhaust to the chaff cyclone. It is a sliding baffle with a wing nut that is very difficult to alter mid roast.

A good way to combat this, is simply to increase the batch size. This technique increases the humidity and moisture in the drum, which will hopefully curb moisture loss in the coffee. Unfortunately, there is a downside.  Additional moisture can reduce the sugar browning process and increase the overall length of the roast. To compensate, I started the roast with a higher charge temperature by +16°F above the control roast and applied more heat from the onset of the roast.

I increased my batch size from 1lb to 2lbs and attempted to roast as close as possible to my control roast ,PR-0124. My goal was to finish within the same amount of time, but at a higher end temperature. On the cupping table, PR-0141 was promising while hot, but cooled poorly. When hot, it had a nice caramel base and a rounded mouthfeel. The volatile acids had suffered and were muted across the board. As the coffee cooled, the age and rough finish appeared in the cup.

THE RESULTS

The favorite roast on the table was the control roast with all of the dynamic volatile acids present. Of the two experimental roasts, PR-0142 reduced the flavors of age better than PR-0141. One thing to note, is that this technique was successful when roasting roasting a dense coffee like the 33765 – Guatemala Huehuetenango Jacaltenango. Coffees from different origins with different flavor compositions, densities, and moisture content will react differently. There are no universals or absolute truths in roasting.

When faced with how to roast an aging coffee, having more tools and techniques to execute is always a positive. Send me your thoughts and your successes roasting aged coffee. We all do it. Let’s talk about it.

Email me: japodaca@royalcoffee.com

NEXT STEPS: BLENDING

In the next part of our Past Crop Coffees series, we will look into the blending and explore how we can use it as a tool with aging coffees.