Recently, our QC & Sourcing Director and Founder Michael McIntyre put a few thoughts down for our team on water activity in the various parts of Sidama and Keffa, and we realized this was exactly the kind of juicy technical stuff our customers love!
In Brief: The Significance of Moisture Content and Water Activity
1) Some moisture content problems are simply due to negligence - lack of fully drying, allowing coffees to be rained on, etc.
2) Some moisture content problems are outside of the control of anybody - properly dried, handled and stored coffees become compromised by uncontrollable circumstance.
3) Some coffees have a unique threshold around moisture issues where cup quality can be relatively uncompromised - that goes both for low and high moisture thresholds.
4) We used to outright reject any coffee with moisture problems. However, in an effort to be better partners with our producer stakeholders and to better understand the threshold limits of coffees, we now focus on trying to find some solutions for coffees that we have committed to if they come in less than stable.
|Catalyst Trade Founder and Processing Director Zelalem Girma Bayou cupping coffees at Lab in Addis Ababa.
A deeper dive on the subject…
Arbegona is a location of very high elevation and nestled kind of in between where Bensa and Bona Zuria districts are located… or at least you have to travel well into Bona Zuria, almost to Bensa, in order to access the roads that lead to Arbegona. Here we find coffees in our lineup like Yaye and Duwancho. Though these areas are relatively new to our sourcing program (and relatively new to coffee cultivation, as Yaye is just now yielding usable coffee crop for the very first time this season), we are observing coffees from these areas demonstrate consistency, most closely related in character to coffees from Keramo.
Generally speaking, we have observed that certain coffees from Bensa possess a robust character that defends against a lot of the negative cup impacts of higher moisture content. Specifically, some of the older varieties in certain areas of Bensa.
It’s interesting, but there is a definite distinction in the robustness of coffees from Hache, Dembi or Odo versus those of Keramo, Bombe and Shantawene. The former are older coffee growing areas with older varieties. This results in clear differences in cup profile and aging.
We observe that an 86-point coffee from those older areas can pretty much maintain all positive characteristics into the lower 12% Moisture Content (MC) range and Water Activity (Aw) readings up to .630, with no loss of point value. There is uniquely no real quality degradation in a lot of these coffees! This would normally fall outside of our comfort level for many coffee types, but it is good for everybody that we understand where the actual quality risk threshold resides.
However, coffees from the latter areas (Keramo, Shantawene and Bombe, along with their smaller neighborhood villages (such as Bura, Murago, Damo, Faficho, Segera, etc.), which are also areas generally known for much higher quality coffees than former areas—these coffees will certainly suffer from quality problems at higher moisture contents. If a coffee from these areas falls into a range of 11.7%+ MC / .580 Aw, an 88-point coffee is at risk of becoming an 85-86 point or less in a short time period.
Coffees around Bona Zuria, including villages of Demeka Becha, Sedaqa and Woranche among others have a lower moisture threshold than those aforementioned areas of Bensa. 11.6% MC and .565 Aw is the zone where we flirt with danger there in Bona Zuria. While this seems fairly insignificant, we have certainly observed these thresholds now over the course of several harvest seasons.
Consistently, top quality coffees from these areas mentioned above tend to give us the very best cupping results when they are situated in the range of 9.6% to 9.8% MC and .430 to .470 Aw. This is historically considered below the acceptable threshold for Specialty Coffee, but we experience many of the most expressive cupping characteristics with coffees settled there. One major benefit we witness to coffees of the lower Moisture Content and Water Activity is extended shelf stability.
It is important to embrace the fact that we are working with an agricultural product, and it is subject to nature and climatic shifts. There are often exceptions to our observations here, but this is a glimpse into some of our efforts to better understand those limits and celebrate beautifully produced coffees in a manner sustainable to all stakeholders.
Being a good partner while maintaining quality
In times past, our response to high moisture content of a coffee was simply rejection. Frankly, it’s still a good general policy to follow when in doubt.
However, over the last couple years, aside from these observations relative to quality and cup score, we have also been observing unique climatic shifts. While it is certainly possible that if a coffee is high in moisture content, it just wasn’t fully dried, we have observed several instances where a coffee will absorb moisture content after arriving at the dry mill in stable condition (meaning moisture was in great shape 10.5%, 10.0%, etc.).
Weather patterns shifting throughout Ethiopia, and particularly in Addis Ababa, are contributing to a new normal. Heavy rains and colder weather patterns for longer periods of time are exposing healthy coffee to atmospheric moisture. Coffee is inherently absorbent, and even stably dried, carefully handled coffee can be compromised if environmental conditions are just right (or wrong).
When this happens, sometimes a preship sample might read 12%+ moisture content when the stocklot was 10%—which was very unusual until now. While poor warehouse conditions will certainly increase the chances to compromise a coffee’s health and stability, we are seeing this play out sometimes even in very high quality warehousing conditions in dry mills. When it happens at this stage, it is not due to negligence on anybody’s part, but rather the coffee becomes a victim of uncontrollable, unpredictable weather patterns that are shifting in Addis Ababa and the surrounding area.
In an effort to be a good sourcing partner with our producer partners and exporters we are working with, if this happens to coffees that we have already approved for processing and are hoping to approve at the preship stage, and if the problem is not due to negligence as in the case with these aforementioned coffees, we will do our best to work with the various stakeholders to find a solution. This is where having boots on the ground, constantly measuring the data on the lots that will become ours, and staying in close contact really pays off. With the right coffees, the quality can be saved and preserved.
How we handle these variations
The moral of the story is that in our observation, there are critical thresholds of Moisture Content and Water Activity all throughout the many micro climates of Ethiopia. Each of these data points help us better understand how to work with producers and be better collaborative partners for these stakeholders, while also providing excellent resources for our customers.
As part of our standard “OQC” (Obsessive Quality Control), we examine each coffee through multiple roast profiles, roasted on multiple machines with different heat applications. This equips us with a rounded understanding of the quality spectrum of each of the coffees we work with. It also allows us to observe how different Moisture Content and Water Activity levels behave in the roasting process. This understanding also gives us insight into what coffees would be best utilized earlier in a roastery and what coffees could age well.
If you have any questions about these topics, hit us up. We hope to centralize much of this information in the future and provide access to our roast profiles.
— Michael McIntyre, QC & Sourcing Director / Founder