There’s a lot more that goes into coffee than the brewing and sipping. That’s just the final step. Coffee is a seriously complex agricultural product, and the complexity of its production stretches from farm to cup. Behind the scenes, all those in the coffee chain use science in effort to deliver quality. This post briefly explores how moisture and density influence the aging process of green coffee.
During the process of sampling and purchasing a coffee, as well as upon its arrival and storage, coffee beans are analyzed for various things ranging from physical defects to moisture and density. This knowledge, coupled with our sensory experience of cupping, is ultimately what guides our decision making processes–whether it’s to purchase a coffee or not, or roast it differently. However, each piece of information tells a little bit of a different part of the story.
To put it simply, the moisture content of green coffee refers to how much moisture is in the coffee bean. This should not be confused with water activity, which is a reading of how much or little water will potentially transform and react with other microorganisms such as mold and yeast. To measure moisture, we use a moisture tester.
When coffee is dry milled, it is ideally dried until it reaches a moisture of around 10-11%. If there is too much moisture, this allows for more reactions with microorganisms. In turn, coffees with high moisture content are more likely to harbor mold, bacteria, etc. Therefore, the ideal moisture range for specialty coffee is 9-11%, with 10-10.5% being the optimal goal. In light of this, with very few exceptions (i.e. new relationships, type samples, etc.), we only sample coffees that are within the range of 9-11%. After all, mold and bacteria are the last things we want interloping in our coffee as they have a great potential of negatively impacting flavor, as well as introducing unwanted mycotoxins.
The moisture content of a coffee bean is also essential to roasting. When there is too little moisture, the coffee roasts too quickly, and results in dry, papery, grassy, ‘underdeveloped’ notes which happen as a result from the outside roasting more quickly than the inside of the bean.
Density is the measure of mass per volume. Perhaps even more so than moisture, density is the biggest prerequisite when it comes to our green analyses when purchasing coffee, with moisture being the second most important in most instances. For density, more density is better since denser coffees decompose more slowly.
To measure density, we simply put coffee beans in a graduated cylinder and analyze how many grams per mL are present.
So what influences density? Soil content greatly influences density, and as a result, what is ‘ideal’ varies not only from origin from origin, but from farm to farm (even within the same region). Generally speaking, 0.7-0.75 g/ml is the ideal range for density. Anything below 0.7g/mL is likely to fade more quickly and storage, and as a result, have a shorter shelf life.
When it comes to purchasing coffee or managing current inventory, we use moisture and density as a guide. Not only do they give us an insight into how they will roast, but they also tell us how long the green coffee may stay shelf-stable. With this information at hand, density and moisture content can make or break a decision, and for good reason.
Now that you’ve learned more about some of the science that goes into coffee, why not sip a little extra slowly to fully appreciate your morning cup. Click the button below to stock up on our Farm to Cup beans at stonecreekcoffee.com, where all orders are shipped free.SHOP FARM TO CUP COFFEE