Water Activity in Specialty Green Coffee.
Water activity theory has been covered extensively elsewhere and this information is readily available.
In short, water activity describes the energy status of moisture in a system.
It is this energy status and not the quantity of that moisture that determines the rate and likelihood of a large number of transformations and processes.
For example, the growth of various molds is dependent on the correct water activity rather than on their being "enough" moisture present.
This is a simplistic take, but sufficient as an introduction.
More details of water activity theory will become clear as our discussion of water activity in green coffee progresses.
This is important because in order to talk about the use of water activity in specialty coffee, we need more than just a theoretical understanding:
We need to understand water activity in our specific product.
Water activity is measured from to What are the Aw parameters for specialty coffee?
How do you know?
If you do not know, how can you talk about high or low Aw in coffee?
We know that water activity applies to us generally because it applies to everything.
How does water activity apply to us in particular in coffee?
In the six years that we've been measuring water activity at Cafe Imports, we've taken around 25,000 water activitymeasurements.
Of those measurements, 10,000 have been longitudinal, meaning that they have been taken from the same coffees over time.
We take the larger set as a reasonable sample estimate of the population "specialty green coffee."
We are not aware of a comparable sample size for water activity measurements in specialty coffee.
This data set covers numerous harvests, origins and regions, varieties, processing methods, grades, preparations, altitudes, and other variables commonly found in specialty coffee.
The primary selection pressures on this data set are those exerted by what people have decided to sample to us and, by extension, the choices we make in weighting our purchases and inventory.
Every sample that is sent to us gets cupped, and every sample that is sent to us gets its Aw measured.
The low end score range of this larger, inclusive set is what most in specialty coffee would assess around 70 points.
A few notes on imbalances in this data set are in order.
It is heavily weighted to Colombian coffees, with around 19% of the total representation.
Nearly 66% of our sample volume consists of pre-shipment samples (PSS).
Between 65 and 70 percent of the samples are Washed.
If coffees from any heavily weighted category
have a unique water activity behavior or characteristic, this may skew the data.
To check on the impact of these biases we'll compare category (origin, type, etc) samples against one another.
The longitudinal data set includes a full range of coffee grades and types while excluding as noise coffees that were not deemed approvable.
The operative exclusion parameter here is contract fidelity meaning that coffee contracted to 83 points needed to cup at 83 points.
This has the benefit of giving us a data set that looks at exactly what we're interested in seeing-approvable coffees and their volatility as relates to water activity.
Unfortunately, this also introduces a potential selection bias that must be checked.
There are numerous considerations when setting up studies like this, just as there are when reading about them.
Our primary interest has been in finding what will help us buy and sell better coffees.
That we see relatively high sample volumes (approximately 5,500-6,000/yr) covering a very broad spectrum of coffee quality allows us some room to extrapolate our findin to the larger industry.
출처 : CAFE IMPORTS
