N. Brancheau
Muggswigz Coffee & Tea co.
A. Haas
Muggswigz Coffee & Tea co.
Abstract
In this experiment, various samples of green coffee that had lost moisture content were rehydrated. These coffees were then roasted both with reduced moisture content, and rehydrated, and then cupped side by side. This was done to determine if improved cupping scores would be attained by rehydrating coffee that has lost moisture content.
Introduction
One of the most common, complex and arduous ordeals with maintaining specialty grade coffee is maintaining it's desired moisture content from the point of harvest and processing, all the way through the multiple climates, environments and months it usually takes to get to the roaster. Coffee is most often transferred via ocean freight, spending weeks and even months at sea. From here it spends time on railroads and in warehouses. All of these destinations have varying climate conditions that can alter the moisture content of coffee significantly. Hermetically sealed bags have aided this problem tremendously. However, not all farmers can afford to go to such lengths to bag their coffees in such ways. And even if they can it's no guarantee moisture level may not be affected at some point.
Hypothesis
We couldn't really find any research anywhere else on this subject matter. There's plenty of research on how moisture content can be lost or can be maintained. But what if you took green coffee that has gone down in moisture content and brought it's moisture back up? When moisture content is lost from green coffee, the very essence of what makes specialty coffee special goes with it. The subtle nuances and potency of aromatics are taken with the water as it evaporates. So, what if you brought the moisture level back up? Would these aromatics be better restored? Would what is left in the green coffee be better reserved? Our hypothesis was that be renewing moisture content to green coffee that was below ideal would improve cup scores.
Methods
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The sweet spot for desired moisture content in green coffee is between 9-12%, with 11-12% being what is typically considered ideal.
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We took samples of three different types of coffees we have in stock: one we roast light (a Yirgacheffe), one we roast medium(Nicaragua Jinotega, Finca Las Mercedes), and one we roast dark (Sumatra Aceh).
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At this point each had a moisture content of 11%. These samples were left to sit out exposed to the air until their moisture content was at 10%.
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Next we placed each sample in a separate air tight sterile container. Sterile cotton was saturated with filtered water and placed inside of the containers with the green coffee samples. The water-soaked cotton did not touch the green coffee, it was sealed in the container but at a distance so that water could be absorbed through the air, not direct contact.
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In a few days moisture levels of the green coffee were up to 12%. We then roasted each of the samples along with a batch of each coffee type from it's original bag in it's original state and moisture content of 11%.
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Blind cuppings of each coffee were done in sequence: light roast original vs light roast rehydrated, medium roast original vs medium roast rehydrated, and dark roast original vs dark roast rehydrated.
Results and Discussion
The results were more varied than you may imagine. In some cases, the rehydrated coffee scored higher. But in more cases the coffee as it was in its original state scored higher. And in all, the variances in score were not that drastic when comparing original sample vs rehydrated sample roasted in the same manner.
Conclusion
Our research provided strong evidence disproving our hypothesis. We conclude the rehydration of green coffee does not have a profound affect on cup quality either way. Since there was no clear evidence of a vast improvement with rehydration, we see the amount of work and effort that would go into rehydration versus the results don't add up to making it worthwhile. But that isn't to say more people doing more experiments such as this should be discouraged, quite the contrary! More research on this topic is necessary and we urge roasters to do more experiments like this themselves and to share the results as well.