Hi everyone!
You may have heard that the key to getting good coffee at home is to grind fresh. (I probably wrote this on my blog as well)
When you buy coffee, if you get them as beans their expiry date could be a in few months, where as if you get pre-ground coffee this tends to be in around 2 weeks. The reason for this is when coffee is ground, more surface area of the coffee bean is exposed. This is exactly why we need to grind the beans when brewing, to get the good stuff out. But this also means that oxidation can happen much more rapidly and volatile substances like aroma escape the beans quicker.
This all makes sense in theory. But I realized that I have not really tested this out. So today I’m going to try a quick experiment to see how much better grinding fresh is. Will it make that much of a difference? Let’s find out!
The Experiment
I prepared three coffee samples with different times from grinding.
Naturally I used beans from the same bag of coffee. I used some Ethiopian single origin beans from Horiguchi-Coffee (Did a review in Japanese if you are interested). These are natural processed beans with a very distinct aroma and flavor. (I kind of wish I used other beans for this test, as you will find out later…)
I ground one sample 1week in advance, another 1day in advance, and the final sample I ground fresh before brewing. The pre-ground samples where stored in plastic bags with the opening tied. They were stored in the same dark room temperature cabinet as the beans.
If you actually buy pre-ground coffee, you will probably be opening the container everyday, exposing it to fresh air each time (which in case of coffee would be a bad thing). So the situation may be even worse than my test conditions.
I ground the beans using the same grinder at the same setting.
Extraction
For brewing, I used the HARIO Switch brewer as an immersion brewer. (Jump to this post for a brew guide)
The beans weren’t very new beans to start off with, so I did not see a huge difference in the bloom from each sample. It did seem like the freshly ground one did bloom the most though.
I used the same water temperature, same brew time, same agitation to keep everything as consistent as possible. Of course the same water was used. I used some bottled mineral water (I did an experiment on water quality in this post and been feeling that water does actually make a difference to the coffee)
Comparison
To remove any bias, I taste tested these 3 coffees as a blind tasting. (I did not know which cup was which, and I did not taste test them before shuffling them.)
The first try
I tasted each cup and I found that one cup was very different from the other two. The other two were pretty similar but one had slightly less spread of aroma and a weaker sweetness.
So I tried lining up the cups in order of; fresh -> 1day -> 1week after grind. I had a feeling that the 1 week one would be the most different from the other two. So naturally I chose the different one as the 1week cup. And chose the better one of the other two as the fresh.
And the result; 1day -> 1week -> fresh…. I mistook the fresh one as the 1week cup… So ashamed of myself.
Just to explain myself a bit, I though from the time differences, the biggest difference will be between the 1day and 1week cups, since after all there is a 6 day difference between them, instead of the only 1day difference between the fresh and 1day cup. This was the reason for my failure… And as an after thought the funky distinct aroma and flavor of natural processed beans also tripped me up.
What I can say from the results is that the coffee degrades very rapidly from the moment its ground. Within a day, it has pretty much hit is bottom and it doesn’t change too much if you keep it for an extra week. I also found that with the pre-ground coffee, a lot of the character of the coffee is lost and it becomes a pretty generic tasting coffee. The fresh one definitely had the most distinct natural processed flavors.
To draw it visually, it’s I had a feeling that the taste will fall linearly like the dotted line, but from testing I found that it’s a much more exponential like the red line.
The second and third tries
To make up for my abysmal failure, I tried the test a couple more times. The difference being that I know what each cup tastes like now.
Having learnt from the first try, I was able to line up the cups in the intended order in both my second and third tries.
Also, as the coffee cooled off, I found the difference between the 1day cup and 1week cup to be more pronounced and it got easier to tell them apart.
Conclusion
So despite the pretty embarrassing result, I am glad that I tried this experiment. I was able to realize really how much valuable freshly grinding beans are to really taste the different characters of the coffee. If you have nice speciality coffee, grinding fresh will be essential in getting the most out of those beans.
This is a very easy experiment to try out, and it’s really quite interesting how different the freshly ground coffee and the 1day off grind coffee is. Please try it out, and if you do let me know what you found!
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