Coffee: A Natural Processing Experiment Part 3 – Results and Conclusion

Welcome to the third and final post in a three-part series on a small-scale coffee processing experiment I undertook in my back yard. The first two posts can be found here:

Coffee: A Natural Processing Experiment Part 1- Processing Methods

Coffee: A Natural Processing Experiment Part 2 – Methods and a little madness

A quick recap:

Late last year I picked a small crop from the coffee trees which are thriving at my parents house in northern New South Wales. Having processed a batch of the same coffee using a washed method a couple of years ago, I decided to try my hand at natural methods. The previous two posts and what follows below describe how things went for two separate batches: one “honey” processed, and the other a “natural” processed batch.

Part of the crop
Part of the crop

Results are in

In summary, the natural processed lot dried really well, however as I alluded to in Part Two of this series, the honey processing wasn’t quite as straightforward. I’ve broken things down a little further on each below.

Natural process

The naturals were a breeze to manage, and appeared to move fairly quickly in the early days of drying. It was fairly apparent early on some of the beans most likely commenced the process with less moisture content than others, as the darkening and progression from red to almost black which occurred within the first 7-10 days proceeded at different rates.

Once this first week or so had passed, the entire batch of naturals were mostly a uniform black colour, and the outer skins began to shrink and harden further. Looking back on some of the guidelines from the Part One post in this series — from Sweet Maria’s on climate suitability:

If a farm can dry coffee from ripe cherry to hard, dried pod in 20 days, it is probably well-suited to DP (dry processing) methods.

If I look at the naturals after 20 days, I think they would have been almost ready to go, and probably could have been removed from drying, hulled, and the bean then dried a little further at that point, resulting in a total drying time of around 30 days.

Natural processed batch across four time points.
Four time points: natural processing.

This is exactly what I should have done, however with a lot of my focus on the honey processed batch, it didn’t really occur to me to just pull the naturals from the drying bed and proceed with the next stage of processing. As I write this it sounds ridiculous not to have done this, however also in retrospect, I at least know what the longer end of the drying scale produces, and I’d rather have that knowledge in the bank and work on a shorter time period in future. Have I ever mentioned before I do these things to learn? I think I may have somewhere along the line.

In any event, the naturally processed batch had dried well, and it was onto hulling – or removing the outer skin, pulp and parchment layer. This was a fairly straightforward process, however with anything more than a very small batch becomes very time intensive. Piercing the skin with my finger nail, opening the dried pulp and pulling away all of the layers together left the just the green been, with a little silver skin which often clings, and is blown off during roasting.

Hulled and ready for roasting
Hulled and ready for roasting

In comparison with the washed processing method (of the DIY kind), if we are talking total effort and time, I found the removal of these outer layers all at once to be easier than the separate steps of pulping followed by removal of the dry parchment post-drying.

Honey process

It was with the honey processed batch that things were held up a little. I’ve mentioned in Part Two about the sticky outer coating of mucilage on the beans — and when I say sticky, I mean really, really sticky.

I had assumed after a week or so this would begin to dry out, which did occur as a warm dry day progressed, however as each day drew to a close and the air temperature fell, the stickiness returned. I even tried bringing them inside at night (stopping short of tucking them in after turning down the bed and laying a chocolate on their pillow) for a number of days however this really had no effect.

At the time I simply pushed on, assuming perhaps after a few weeks I’d have a dry batch, however this wasn’t so. Of course my error here was assuming an outer dry layer correlated with drying of the inner bean. I’ve yet to work out an exact relationship between the two, however I’d they are in some way related.

At around day 16 or 17 the first signs of dark spots began to appear on the outer surface of some beans. I proceeded on the basis I would either end up with a batch of beautiful “black honey” processed beans, or a heap of mould. I had my hopes on the former, however fully expected the latter. Remember at this stage things were still quite sticky, so I thought I had a way to go before they might be ready. In reality, it took another 10-12 days before the black spots began to increase. After around 38 days, it had well and truly taken hold of many of the beans.

Four time points: honey processing
Four time points: honey processing

So, by that stage I was indeed left with what appeared to be a pile of mould. The evenness in appearance of a true black honey processing method was replaced by what definitely appeared to be groups of black spores enveloping each bean. It was time to cut my losses and proceed only with the naturally processed batch.

A few lessons

First, I’d pull up stumps earlier on both batches of beans if I’d had my time again. Waiting for the honey processed batch to dry further was probably an exercise in futility. In doing so, I inadvertently left the naturals a good deal longer than planned (at least a coupe of weeks longer).

Also, plan on life getting in the way a little. By the time I had really decided the drying time was probably done, it was another week to remove the hulls from the naturals, and a further two until roasting. Not the end of the world, however when most things are limited to weekends, it’s not hard to blow out a scheduled timeline by weeks at a time. That said, I’d rather have that happen than not try this at all.

After all was said and done, I did actually venture back into the shed and remove the parchment layer from a couple of beans in the mouldy honey processed batch. Surprisingly, the bean appearance was reasonably good, however by that time I had already decided to abandon them — probably the wisest choice given the amount of mould on those outer layers.

If you are considering processing your own coffee at home, my advice would be to stick with a fully washed process, or if you are looking to dabble in some dry methods, perhaps go with a straight “natural” process.

Also, having now tried both wet and dry processing methods, I can offer the perspective that in a backyard DIY situation there is a little more work at the “front end” of the washed processing, however after that first week of pulping and washing, there only remains the hulling — or removal of the parchment layer once the beans have dried out.

By comparison, in a natural processed batch, there really is minimal effort required at the front end of the process, and come the time when the dried cherry is pulped and hulled, all layers come away pretty easily, and all you have left is the bean — ready to roast. On balance, looking at the total effort involved with each, I’d come down in favour of the natural processing method. Remember, the issues I had with turning the coffee during the drying process were all related to the honey processed batch. The naturals? As simple as running your hand over them or giving the drying frame a bit of a shake.

Concluding the processing

Reading through what I have written above, you may get the impression getting the coffee this far was all a little too hard, and perhaps not worth the time overall.

Nothing could be further from the truth, and I will definitely be processing more coffee naturally in future. Honey processing? Probably not — I’ll leave that to the experts in Costa Rica, and many other countries now processing this way.

For future batches though I’ll probably begin by limiting the drying time to around 20 days or so and see how the roast and taste compares with the current batch of 50 days duration. From there it’s only a matter of altering the time frames for further experimentation. I’m definitely looking forward to pursuing this further in future.

The remainder of this post will focus on the naturally processed batch, given the outcome of the honey processed lot detailed above.

Roasting

Once processing was complete, it was time to turn to roasting. Something which would be a fairly delicate task given the size of the batch remaining.

Remember, I began with 210 grams of coffee cherries in the each group. After the drying, the Natural crop had reduced in weight to 100 grams, and after de-pulping: 46 grams — a fairly small batch to roast. However, roast we must — otherwise everything to this point becomes fairly irrelevant.

A successful roast
A successful roast of the naturally processed batch

The plan was to brew the resulting roast by filter, so a light to medium roast was in order. For those who may be interested, checking back on my roasting notes, the total roast time was 11 minutes, with a development of 19%.

Drinking

Having climbed the mountain, we were now at the summit, and the amount remaining to brew? A healthy 37.5 grams of roasted coffee, which had rested for seven days post roast and was now ready to go. Given I had a few tasters (family members) around the table, we had one shot at it, so with the hope my grind setting and brew recipe were somewhat close to the mark, away we went.

  • Coffee: Nine South Estate 2015 Natural
  • Region: Alstonville1 NSW, Australia
  • Grower: L & J Denison
  • Elevation: 140 m
  • Processing: Sun-dried Natural
  • Crop year: 2015

So how did it taste?

The result: shared with those who produced it
The result: shared with those who produced it

In all honesty, better than I expected. Sure, it wasn’t the pinnacle of fruity naturally processed greatness, however overall I would describe it as very well-balanced, with medium to light body, mild citrus acidity, with the predominant flavours woody spice and a hint of chocolate. Although not overpowering, there certainly some of those earthy flavours which can be apparent in naturally processed coffee, and these were also evident in the dry aroma after grinding.

A very enjoyable brew, for which I admit to being quite thankful for given the process leading up to actually tasting the stuff. My group of tasters around the table? In summary, I’d say there was general acknowledgement the whole process had been a success, given what was now being consumed. Mostly, the “actually that’s not too bad/pretty good” comments you expect when taste testing something you may be a little dubious about initially.

Of course it would have been sensible at this point to have on hand a sample of the same coffee processed by the fully washed method wouldn’t it? It’s probably a little late to think of that when pouring the brew into the cups. Another for the “in retrospect – this is what I will do next time” file.

In conclusion

I began this natural processing experiment in the knowledge at some point in the next few years I will need to be processing the fruit produced on the coffee tree now growing so well in my back yard.

Where it all began
Where it all began

Having previously managed to process a batch using the wet or washed method successfully, I was keen to see how a naturally processed lot turned out in comparison. In summary, I’d say I have a way to go with both methods, with some experimentation still required as to the length of the drying time with my naturals; and more efficient methods associated with the wet processing. Of course the joy in all of this is the amount of taste testing required to assess the results from tweaks in my processes.

After completing my first foray into natural processing, I think I’ll leave the “honey” methods to the experts, having found this more difficult every step of the way, however I certainly plan to be using the power of the local sunshine for some more natural process drying in future.

I hope you’ve enjoyed reading this series of posts, and perhaps learned something from them — I know I certainly have. Signing off with a special message from the honey processed batch: ”thanks for sticking with me”.

 

  1. The town I grew up in before moving to Brisbane in 1990. ↩︎

Coffee: A Natural Processing Experiment Part 2 – Methods and a little madness

Welcome to the second instalment in a series of posts describing my use of dry processing methods to take a small batch of coffee cherries from the tree and into the cup. If you missed the initial post, you can find it here, along with a series of posts from a couple of years ago on washed processing methods which I have recently combined and republished.

Since publishing Part One some weeks ago, I’ve been crunching a few numbers (I do mean just a few: no complex algorithms or statistical modelling here), and hopefully can present something coherent about how this whole thing proceeded.

My expectations

To recap, I am experimenting with two dry processing methods: Natural processing, where after picking, the whole coffee cherry is simply laid out and sun-dried. Once the whole cherry has dried, depulping and hulling then follow. The second is Honey processing, where the flesh or pulp is removed from the cherry first, leaving the sticky mucilage layer on, with the beans then laid out and sun-dried.

At the outset, I planned to have the beans drying for three to four weeks or so, remove the pulp and mucilage from the naturals, and allow them to dry for a further week before roasting. The honey processed batch? Well, that was anyone’s guess, as I really had no idea how long it would take for the sticky mucilage to dry on the outside of the bean — particularly in a climate known for its humidity. Time would tell me, or so I hoped.

For that matter, I wasn’t even entirely sure as to how I would tell when the drying process had reached a stage where roasting would then be possible. I have mentioned the often quoted 12.5% moisture content in previous posts, however I do not have the necessary equipment to readily determine the exact moisture level.

Time and estimation would have to do.

Tools

I say tools — however there was really only one: my custom-made raised drying bed. Sounds pretty fancy when described like that, however it consisted of a flyscreen-covered picture frame sitting across the arms of an outdoor chair. Fairly rudimentary, however not a great deal of complexity is needed to ensure adequate ventilation and airflow.

IMG_4915 IMG_4923

Other than that, it was simply my iPhone for recording photos and data, Day One app as I’ve mentioned in a previous post, and a couple of bowls for both beans and debris when depulping the honey processed lot and eventually the same for the naturals after drying.

Methods

Before we get too much further not things, I probably should mention upon beginning this whole process, I had 420 grams of coffee cherries by weight at my disposal.

IMG_4919

These were split into the two groups evenly, with 210 g into each of the natural and honey processed groups respectively. Of course this reduced quite significantly in the honey group once the pulp was removed, however I did not check the actual weight again.

Initial processing

As you can imagine, the naturals required zero processing to prepare for drying, with the exception being to check for any bad fruit.

For the honey group, this amounted to depulping or removing the skin and outer flesh by hand, leaving the sticky mucilage covering the parchment layer on the outside of the seed or “bean”. Not an overly onerous task, however at any great scale would require significant time and effort — or machinery.

IMG_4929 IMG_4930

Once complete, out on the drying rack they went, with a Day Zero photo taken, and we were under way.

Drying

Over the course of the drying period I followed the same routine to ensure the beans were regularly turned, and also covered from any dew which formed in the evenings:

  • at around 6 am each morning the chair and drying rack were placed out in my back yard in a position of full sun;IMG_4934
  • a photo of each batch was taken and uploaded to Day One with additional humidity data from the Bureau of Meteorology (courtesy of the Pocket Weather Australia iOS app);
  • any additional comments were added to the entry;
  • upon returning home from work, both batches were manually turned, with the drying rack placed back under cover of the patio roof, ready to repeat the process each day until completion.

It was during this process a little bit of madness set in. As I have mentioned on numerous occasions, the mucilage remaining on the honey processed batch was quite sticky. If you’ve ever had to move and turn numerous small sticky objects you’ll invariably understand the ensuing challenge.

By hand, well… the beans simply stuck to my hand. By a plastic IMG_5086paint scraper… the beans simply clumped and stuck to that. Eventually, I resorted to simply turning them by one by one. Wait…what? Yes, that’s right, flipping over each little bean and placing it softly down again on its little bed for the night, only to have it face the searing sun again the next day.

One. At. A. Time. Like I said — madness.

Despite this insanity, the routine worked well over the weeks this IMG_4995whole process took, with the exception of a few days where I was either home late or in a rush, and didn’t stop to turn them or record data and photos. In any event, each night they were in and the following day back out. During some stormy weather for a few days during the middle of the drying period they were also left under cover during the day. Better safe than sorry.

Final processing

Once the drying process was complete, we end up with essentially the reverse to how we started. The naturals required depulping, and for the honey group, only removal of the final parchment layer to expose the bean inside.

Just to be sure I planned to then leave the beans a further week before roasting.

The data

The result of the data recording in Day One was a 64 page PDF export containing basic data such as day, date and time; weather information (temperature and description); a photo record of the bean appearance, and any additional comments I made for the day’s entry, which importantly included a record of the relative humidity at the time — a known enemy of natural processing.

Although there were 64 entries, these were made on 32 individual days, with two entries per day the result of taking separate photo of each of the natural and honey groups each day. Although it might have been nice to upload two photos on the one entry, that was not a feature available to me at the time, however it is now, with a fantastic recent update to Day One.

Drying progress one week in.
Drying progress one week in.

Further to this point, although the entries were made on 32 individual days, with a few days missed here and there for various reasons, the entire process spanned 50 days in all — perhaps a little long, however we will get into that later. Typically around the time I begin entering data into a spreadsheet is when I also realise a few additional data points or variables collected may have assisted the overall analysis a little — this time was no different. Upon adding the temperature data, it soon became apparent the numbers probably didn’t quite reflect the actual temperature during the day, when those little beans took one for the team, and spent many hours in reasonably hot sun.

When entering the numbers I found myself thinking it had been a very mild October compared with how I remember it feeling day-to-day. It wasn’t long before I realised this was largely due to the fact that the times I had available to snap the photo and add the Day One entry, were either before or after work. Of course both these times occurred when the temperature had either yet to rise, or was already falling — really, must an occupation get in the way of everything — particularly hard-core science?

Thankfully, gathering additional data retrospectively is what we have the Internet for. The Bureau of Meteorology kindly helped out with mean, maximum and minimum temperatures, and a few other pieces of information such as rainfall and average sunshine over the course of the drying period. Would all of this additional data make any difference to how I conducted the drying? Absolutely not, however I think it does provide you with some idea of the conditions at the time, and perhaps whether or not it might be something you’d try yourself relative to how things turned out.

So, those numbers:

  • Drying period 50 days through October/November (Southern Hemisphere Spring);
  • October mean temperature range 16.3 – 27.1 degrees celsius (actual temperatures 12.9 – 33.8 degrees celsius);
  • November mean temperature range 19.8 – 29.2 degrees celsius (actual temperatures 16.1 – 33.4 degrees celsius);
  • mean hours per day of sunshine: October 9.1 hours; November 9.2 hours;
  • Total rainfall: October 55.8 mm; November 74.2 mm

What good is recorded data without a few charts, so I have included daily temperature and humidity recordings below, along with my own bean turning degree of difficulty score — which I understand is quite complex, however if you look hard enough I think it tells a story.

Screen Shot 2016-03-13 at 6.29.10 AM

Screen Shot 2016-03-13 at 6.29.29 AM

Screen Shot 2016-03-13 at 6.29.56 AM

Next: results and a few lessons

This post has started to become a little lengthy, so I have split off a closer look at the results and outcome for next time.

I’ve said it before and I’ll say it again here: the absolute best thing about writing this blog (beyond the knowledge that a few people actually read it), is what I learn along the way. Not simply from the research and dodgy backyard experiments that ensue, but how the act of writing makes me think a little more on the results, and what I might do differently or look into further next time. You know, that realisation you sometimes get: “well now that I say it out loud I’m not sure if it really is such a great idea”.

I hope you’ll join me for a few more realisations in the next post.