Hi,

I'm currently trying to develop my "perfect" aeropress routine and have recently had an idea. It might be completely wrong, but here goes:
- the brew water temperature affects the speed of extraction (hotter = faster) and what is extracted (hotter = more acidity; colder = smoother, more body).
- this is often a trade-off, esp. with more acidic/lighter coffees that benefit from higher temperatures (97°C) - you want the high temperature for the acidity and aromatics, but can't keep it there long enough for enough body because of overextraction (esp. when your grinder is not perfect, there are fines).
- so I thought, why not start the extraction with high temperature, let it brew for some time and then finish the extraction with lower temp water (85-90°C). this will get me the acidity I want, but also some body and richness without overextracting.

The routine is roughly as follows:
13g coffee/200ml water/medium-coarse grind (cupping grind, not quite french press)
inverted aeropress
bloom the coffee with 100ml of 97°C water, stir, brew for 45-60s
top up with 100ml of below 90°C water, stir, screw on the filter
after total extraction time of ~1:45, flip and press, stop just before hissing.

I've had some fairly interesting results, but I feel it's not IT yet. am I completely off mark here? is my theory/reasoning completely bunk, or is there something to it? could the effect of temperature be exploited differently?

I have no data to support this but I think/feel it's the strike temp that has a big impact on acidity vs sweetness. As the brew steeps in an inverted Aeropress, temperature drops...all the way to room temp if you let it

By adding half the brew water at 97C you are probably not capitalising on the benefit of the higher temp (coffee & brewer acting more like a heat sink, a more concentrated slurry may retard extraction)?

Smoothness & sweetness also come with higher levels of extraction. Body can be manipulated, but too heavy can blunt flavour, but that's personal preference.

With your short steep, flip & plunge, with a coarse grind I suspect you are getting more of an augmented percolation, the steep has allowed a degree of infusion, then the plunge picks up a little more TDS from the bed, depending on how hungry the water is for it. The longer you leave it, the more your brew will swing towards immersion, from percolation (but probably always pick something up from the bed at plunge).

Try grinding much finer, flip right after combining grinds & water, wash any grinds off the bung by swirling, then steep. Using the plunger as a "lid" seems to help retain heat better.

If you are looking at steeping at 85C, then your beverage may only be 65-70C (guess?), so why not start hotter & brew longer to get to a similar end temp?

my theory behind not using 97 strike temp for the rest of the brew is to minimize the chances of over extraction...
I know I don't care for using just 85-90 temp for the whole brew (and a lot of Aeropress guides seem to recommend this range for some reason) - I suspect they only work with a lot of updosing (to make up for underextraction).
The combination is an attempt to get the best of both worlds. Just don't know if I am at a right track or not. Does it at any level make sense, to combine two temperatures?
I will try finer grinds. But I have made some overextracted ones at finer grinds, that's why I sort of wandered into FP-like territory.
The more I am experimenting and the more I am reading, the more I feel I just start sifting the grinds - this would get me to higher extractions without dryness/bitterness I get more often than not when I try to push things. (Hario Mini Mill (even with the tape mod) is not the perfect thing when it comes to grind distribution)

That's funny, we were both posting Aeropress topics at the same time.

My routine is 20g almost espresso grind, 200ml, 180*F(82*C) water, 10-second steep.

I use the inverted method. Bloom with 100ml for 10 seconds with aggressive stir and put pot back on heat source. Put the rinsed filter on and turn right side up over cup. Remove plunger and fill with balance of water. More stir. 20 second plunge. Flawless every time regardless of coffee.

I can't seem to get what I'm looking for with coarser grinds.

Hi Matheus,

I've often questioned the assertion that higher temperature alone leads to more acidity. My experience tells me there's more to it. When my brew temp drops, I generally get a shot of acidity, even to the point of sourness. But this requires some qualifying.

I used to brew using a CafeSolo. Once, when I tried post-filtering the brew using a Hario cone, the long exposure at room temperature caused a very sour result. I've also heard others describe sour results when using a syphon brewer if they let the temperature fall too soon. Finally, I had used a Sowen SoftBrew porcelain pot, which typically loses heat very quickly. My results have always been fruitier and on rare occasions sour when compared to the CafeSolo. But this still requires one more detail before all is made clear.

In the case of the CafeSolo, the initial brew temperature was not as high as either a syphon brewer or the SoftBrew (which I nuked in a microwave to a boil to preheat the porcelain). But because the CafeSolo was insulated, it didn't experience as much of a temperature drop, resulting in mostly roasty flavors, and a hint of acidity. The SoftBrew exhibited a much stronger hit of acidity. But what I believe brings out the right acidity (as opposed to just sourness) isn't merely the high temperature, it's the rapid temperature drop from high to med high heat.

Finally, to further confound the issue, I now brew using a Trifecta MB. Way more acidity if you hold back on the turbulence, but always fruity, never sour. It uses a 50 sec. brew time and not very high temp water. The pressurized press-out helps quite a bit in extracting the full flavor, and the whole setup is very similar to an Aeropress in functionality.

So what might one conclude from all this? Beats the heck out of me! Hope this helps in any case.

Oh, nuts, I left out another crucial detail. I believe the agitation I applied to the CafeSolo probably explains why I was getting so much roasty flavor and so little acidity. Increased agitation using the SoftBrew also sermed to reduce the apparent acidity. But because such agitation was applied halfway throught brewing, it reinforces the notion that you will only get a shot of acidity when the temperature starts to drop AND the brew hasn't yet been saturated by other solubles. At least, this is what one knowledgable brewer once told me when I asked how I could achieve a less acidic balance on the SoftBrew. He said to grind finer, which will cause the solution to become more saturated with other solubles and pull less acid out as the temperature drops.

matheus wrote:my theory behind not using 97 strike temp for the rest of the brew is to minimize the chances of over extraction...

I always brew inverted at 96-97C, the longer you steep the less chance of overextraction (sounds wrong I know), because the more coffee, of an even concentration, you have above the bed.

You could also try leaving the brewer inverted & periodically tasting off the top with a cupping spoon, plunge when happy.

barkingburro wrote:Hi Matheus,

I've often questioned the assertion that higher temperature alone leads to more acidity. My experience tells me there's more to it. When my brew temp drops, I generally get a shot of acidity, even to the point of sourness. But this requires some qualifying.

Hi Barkingburro, I think there may be a distinction between acidity, sourness/acidic coffee? When I get higher acidity due to higher strike temp (but at a decent level of extraction), the coffee is still generally sweet & juicy (in the way that peaches & grapes are?), as opposed to sweet & more "syrupy"? Acidic, sour - these strike me as less desirable and likely signs of underextraction?

I hope perhaps you or someone else can help explain why underextraction could lead to sourness. I don't exactly have a clue about this stuff, just my own observations. If what you're saying applies to the SoftBrew, I would say my use of that device is right on the edge of underextraction, because it most often yielded a sweet and fruity brew on appropriate coffees that featured berry or peach, etc., flavors, but teetered on the edge of sourness--and it generally produced a weaker display of the spice and roasty flavors than my CafeSolo. The CafeSolo was pretty much the opposite--generally a very full extraction with sought-for fruitiness only rarely appearing, and never sour.

The Trifecta is, of course, off the chart and an anomaly compared to these two brewers.

I think the Sowden Softbrew is prone to underextraction (compared to similar steep times in French press & Eva Solo) because grinds are contained in the smaller volume of the permanent filter. I have found longer steeps necessary with the Sowden to hit flavours comparable with brewers that have the grinds steeping free in the brew water (same grind & dose). The porcelain retains heat well, so it well tolerates longer than typical steeps.

Acids extract relatively early, later components in the extraction help balance the acids & tame sourness/overly acidic coffee.