Barrel-aged Coffee | What We’ve Learned So Far

Today I took our third batch of Midnight Harvest from its fresh oak bourbon barrel. With the gentle hum of the roaster behind me, I realised that this current batch would mark a more enlightened approach than we’d taken thus far.

A little over two months ago, we conceived the idea of barrel ageing some of our specialty coffee as a one-off single run. Little did we know, there’d be such a demand for the resulting coffee, that we’d soon be welcoming it as a staple offering in our arsenal. The feedback on the last two batches has been somewhat astonishing, and I’m keen to share some of what we’ve learned in the process.

Can you use any coffee?

I must admit I assumed the answer to this question was yes (with the prerequisite that the coffee used was of specialty grade). I think I jumped to the conclusion that the coffee itself would be dominated by the flavours of bourbon and leave little or no trace of terroir. Oh, how wrong I was…

The very first batch…

Does the coffee’s processing method affect the result?

It certainly does! The first coffee out of the barrel was a honey processed coffee from Nicaragua. The honey (or pulped natural) process is when the coffee cherries are de-pulped, and the mucilage (sticky substance) coating the beans is left unwashed and dried immediately.

This method (when controlled) well leads to a coffee having all the hallmarks of natural coffee but with more clarity in the cup. There is also the benefit of less water used in the processing.

Round 2 was a washed Guatemalan coffee. Washed coffees tend to reveal brighter, more acidic characteristics. When fermented and dried in a controlled environment, they offer sweetness and super clean results in the cup.

The results between the first and second batch of Midnight Harvest did indeed show signs in the end cup due to their processing methods. The Nicaraguan coffee was so powerful in its taste and aroma that it filled the whole roastery every time we brewed a cup.

Midnight Harvest 2.0 – a washed Guatemalan this time.

It was super boozy and decadent with bags of stewed fruit sweetness. The Guatemalan, on the other hand, had a more subtle bourbon aroma. The taste was more refined and cleaner – with a slight berry tang. Just what I would expect from a good, washed coffee, especially one that had been hanging out in a bourbon barrel.

Does altitude play a significant role in the result?

I think so. Higher grown coffees tend to be denser due to cooler climates at higher elevations, meaning the coffee will take longer to mature on the tree. This leads to denser, less porous beans. Lower altitude coffees tend to grow quicker, and so are less dense and more porous. This was reflected in the amount of bourbon characteristic in the Nicaraguan first batch, as the beans were grown at nearly 700 meters lower than the Guatemalan coffee.

This was certainly reflected in the cup with the more porous, lower grown Nicaraguan coffee absorbing more of the bourbon flavour than the Guatemalan.

Does the length of time in the barrel have a significant impact on flavour?

For sure. This is still an ongoing experiment for us, but we are leaving the coffee to age in the barrel anywhere from 2-4 weeks depending on demand. We currently roast our first batch after 2 weeks of ageing and only extract what we need from the barrel for each roast. We can easily fit a full sack (60-70kg depending on origin) and roast in 15kg batches.

The first batch only lasted 3 weeks and produced a stronger bourbon flavour from the last batch. This was also replicated in the second batch. Although this coffee produced a more subtle bourbon flavour from the start, there was a notable increase of both aroma and flavour in the last batch we took out of the barrel. This batch also lasted an extra week, so 4 weeks in all.

Are we excited for the next batch of Midnight harvest?

The answer to this is a resounding yes….

With two barrels under our belts and armed with slightly more data we are moving onto batch number 3. We want to produce the best tasting batch yet and the slightly more informed barrel ager in me thinks you will not be disappointed.

Buy Midnight Harvest here.

Happy brewing,

Burton

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