The Wild Drink Blog

So, for simplicity’s sake I have chosen to process the coffee in the Sumatran & Brazialian pulped natural/semi-wet style. This is, as it says on the packet, a cross between the wet and dry processes. As seen on the previous post the cherries are hulled but the slime covered beans don’t go to fermentation tanks, they are instead dried for a week or so. The resulting dried coffee should take on characteristics of both wet and dry processing, sweeter and more body than a wet processed but still some acidity which can be lost during full on cherry dry processing.

The drying conditions for this process require lower humidity so that mucilage can dry quickly and not ferment or develop mould. So that I could monitor the coffee as much as possible I chose to dry it behind my bar at work. I knew that humidity reader on the new Plus 4 U would come in handy eventually! On any given day the humidity around the coffee machine would fluctuate around 30-50% contributing factors being the steam wand, glass washer, cup warmer and water boiler. In addition to humidity, the other important factor is temperature. Once again I was able to get pretty close to the temperatures in producing countries by putting the beans on top of the coffee machine with a fan to circulate the air and regularly moving the beands around for even drying.

Ambient temperature 29.3°C - Humidity 40%

note: The is a certain irony to drying beans on top of a coffee machine - ‘Which came first, the coffee bean or the coffee machine?!’

Now I realise there are imperfections in this situation. The humidity may be bit low which might make the beans dry too quickly, as I understand it this can make the beans become greyish and weak. Temperature fluctuation might not be great enough, we turned the cup warmer off over night and temperature drops by about 10°C but as with bourbon casks I would imagaine the expanding and contracting of the bean daily has some effect on the final outcome.

Having said all of that the process has run at the sort of rate that I would expect it to. A week on and the beans are nearly there, let’s have a look at what has happened over the last few days…

Day 2

Not much to report, mucilage is still there and it’s like stirring dried up baked beans that were microwaved a few days ago! They still stick to each other but during the course of the day seem to be getting less and less sticky.

I would imagine with a few hunderd Kg this is quite a critical stage in avoiding mould formation.

Day 3

As you can see form the picture, the mucilage has almost completely dried forming into a parchment shell. It’s still slightly glossy to look at and obviously not dry, reminds me a bit of a raisin, dry to touch but plenty of moisture under the surface.

At this stage it’s not really possible to open up the parchment without damaging the fragile bean below which is currently quite pale in colour.

We also picked out a few rotten beans which had probably had insects in them eating away, they are obvious due to large black sections showing through the translucent shell.

Day 4

With care i’m able to open up the parchment which still does quite a good job of keeping th bean hidden. Underneath is a fragile fibrous bean of dark black, it can easily be bitten through and has a bit of a way to go yet.

It’s good to start seeing a coffee bean finally after all the picking, pulping and drying!

Day 5

The Parchment is now completely dry to the touch and comes off a bit easier. underneath the bean is still black although biting it is tougher but still makes a dent and eventually breaks.

You can see green bits emerging from the edges as it begins the final stretch towards dryness.

Day 6

Parchment comes off easily and underneath the bean is beginning to lighten in colour fully as we reach 15% moisture (estimated). Still a small dent when bitten but pretty much impossible to break now.

It’ll need to be monitored over the next 24 hours because we’re almost there I reckon….

Day 7

Finally it looks like we have a dry coffee bean. The bean cannot be broken when bitten and barely even scratched, parchment is similar to removing the shell from a pistachio nut, a crack and it flakes off. Most beans have no black spots on them though the silverskin is a bit of a pain to remove on some.

So it’s time to test the beans moisture level which should hopefully be between 10-12%, then they can be stored ready for roasting. But there is a problem, the moisture reader which has been kindly provided to me by Stuart of Masteroast requires about 200g of green coffee to give an accurate reading. Yes, that’s right, after all that hard work i’m left with only 130g of green goodness.

This is the first time i’ve used a moisture reader but from what I can gather it works something like this. You put the beans in a narrow circular container which is the lightly spun around by a motor for a couple of seconds. The motor is then stopped and I think it calculates the momentum and from that somehow generates a moisture percentage. I’m sure there’s more to it than that but I can’t find anything on Google.

So back to our problem, 130g of beans is scoring about 7.5-8.0% which sounds too low (the beans have been dried too much), but this could be because it’s not the full 200g dose. Fortunately Stuart was only a phonec all away and he did a test at his end with a reduced dose on beans known to be in the 10-12% threshold. His test produced lower results than normal (about 9%) proving that my beans do have slightly more moisture in them than the indicated 7.7%… but they are probably still a bit on the low side.

So for a first attempt these are OK results. It’s a bit annoying that the moisture reader wont read smaller amounts which would allow me to constantly monitor the levels throughout drying. Next time I will have more insight as I see the colours change and I have also been offered the use of a UV panel to simulate sunlight which should be interesting.

Again, if anyone has any further knowledge on any of these subjects please let me know, or indeed any mistakes I have made along the way.

I’m going to roast and cup this batch to see what it’s like but it’s the next attempt that i’m really looking forward to!