Moisture Content in Green Coffee

WOLFF WEEKLY VLOGG 006 | Peter Wolff Chatting about Moisture Content

With moisture content, it is basically the residual moisture that is left behind in the cherry from the processing stage. There are two components to the moisture content. We have free bound moisture content and we have chemically bound moisture content as well. It is a by product of the processing of the coffee. Also, coffee is a fruit, so it has a natural moisture content to it.

Moisture content in green coffee is very, very important. We need to look at this as part of our quality control practices when all new green coffee comes into the warehouse. The main thing to think about it what’s acceptable in terms of stable coffee. For washed coffee we would be expecting the coffee to land between ten and twelve percent moisture content. For natural processed coffee we’re looking between ten and thirteen percent.

One of the things we’re really wanting to understand is to ensure what we’re getting is in spec and is at a stable level. If the moisture is less than ten percent we can have a lot of problems on our hands as a roaster, that being that we may have past crop coffee that’s arrived. It may mean the coffee has not been dried correctly. When the fruit is less than ten percent it’s going to show lots of signs of aging in the cup and this is something that’s quite a concern for us.

Anything that arrives to us and is above thirteen percent - we tend to find that more of a risk for those kind of coffees that particularly here in Australia that would be coming from New Guinea or Sumatra or Indonesia growing areas and that aren’t packed in grainpro bags. If they are coming in at a higher moisture content, this will mean that the coffee is going to roast very unevenly. It’s going to be a little bit unstable in the roaster for us. It does create a different set of difficulties for us to get that evenness to it. My recommendations, if that is the case, that your coffee arrives at a higher moisture content above thirteen percent, is to leave it standing in the roast house and let that coffee naturally settle down below thirteen percent.

How we test for moisture content is basically a moisture meter. This is a really basic, entry level one and I think it’s really quite good because it runs off a couple of nine volt batteries. It’s very transportable. It’s very good, particularly if you want to take it to origin - chuck this in the backpack as well. It’s really quite handy. It’s very simple to use. We just take a sample of the green coffee. We screw the top off, like I’m doing at the moment. We add the green coffee level to the top and drop the lid back on. Then we screw it down so it’s firm and then quite simply turn it on, hit the test button here on the front and then we allow it to go through it’s testing process. The best thing to do is take three separate samples and average them. That will give you a reasonably accurate sample of what the moisture content is like.