Espresso brew pressure - impact on flavours

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theiguanaoz
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Espresso brew pressure - impact on flavours

#1507

Post by theiguanaoz »

This is more an observation, and I apologise in advance if it’s common knowledge, but it may help a newbie like me explore the potential of their roasts even further.

For some time now I’ve been running my espresso machine at around 8.5 bar at the pump (typically 7.5-8 at the group head) and what really comes through on my KL roasts are fruity, sweet, and bright notes.
Compared to our local roasters, these are the cleanest cups I’ve had.

Since I’ve had my KL, this has meant that 1.4-2.1 has been (quite literally) the sweet spot. Guatemalan Huehuetenango stands out to me as a favourite bean.

What I’ve been craving is the ability to roast those cocoa notes with enough punch to cut through milk. I prefer to use s 15gm VST to make my coffee go farther, but less coffee means it needs to cut through well.
This morning I increased my pressure to 10 bar on the machine to test an idea I’d read that lower pressure brings out the bright notes, and higher pressure the caramels and chocs
10-bar at the pump gives me close to 9 bar at the group head (how the machine came configured). I’ve always found this to be the best setting for classic espresso. I also have a PID but keep it at around 94c unless very light or dark.

I ran some Brazil Cerado roasted RTD last night, after just having run two shots at lower pressure.
The difference was amazing! Both Cerado shots were interesting – perfectly drinkable and enjoyable which is a credit to the KL. But the higher pressure shot brought out the choc-caramel notes. The lower pressure is more what I would describe as bitter cocoa – it was there, but overpowered by brighter notes.

It’s a reminder for those of us who can to adjust the OPV to suit taste, and to factor this into your objective for a roast. In my experience so far, the claims seem to be true that lower brew pressure highlights the fruits and higher pressure the chocs.

I like the caramel and milk choc I got in my latte at the higher pressure. I plan to roast for Rest so I can do up a larger batch of back to backs.

It’s nice to make these discoveries now I don’t have to worry about the quality of my home roasts, as they’re all stunning using the existing profiles on the KL vs my bread maker and clear lack of roasting knowledge and experience.
BenN
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Re: Espresso brew pressure - impact on flavours

#1508

Post by BenN »

Thanks for sharing. It's a great reminder. :)
Ben
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Wayne
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Re: Espresso brew pressure - impact on flavours

#1509

Post by Wayne »

Hello theiguanaoz

Thank you so much for the post .. What a discovery . It makes so much sense .

Just 2 questions from my side . what machine are you espressing off that you can adjust pressure ? Can you adjust the pressure while the espresso extraction is happening ?

I started playing with pressure profiling years ago when the Lamarzocco Strada hit the scene . Its amazing what you can do from a flavour perspective .

I learnt about espresso flow dynamics . The first 33% of the espresso I found was super intense . Almost the heart of the espresso . Massive amounts of flavour . Beautiful sweetness and balanced acidity .
Pressure wise - Full 9 - 9.5 bar of pressure for the first 12 - 15 seconds . when I assessed the TDS % its was super high.

Second 33% is a short , sharp and body filled extraction where I came off the pressure over 10 seconds - 9 - 7 - 5 bars . This phase is all about how much body I can draw out .
As the coffee in filter basket increases with intense heat and the puck is now completely saturated , flavour is non existent . It's all about body and bringing balance to the first part .

The last 33% is a 5 to 6 second spill at 2 bars pressure . I don't actually want too much of the tail . It's bitter and the longer you extract , the more intense the bitter aftertaste becomes . You however need that controlled bitterness to help balance the coffee.

The last part of the above is typically the baristas curse . If you get your extraction wrong with too course coffee or not enough in the basket , you end up with the ratio skewing to the bitter end side and it really drowns out the coffee taste through dilution . The same issue exists when extracting an espresso to your usual 30 seconds . By the time the coffee extraction reaches 15 seconds , it is blonde and moving towards an almost translucent colour . The next 15 seconds at 9 bars pressure is all bitter tail ..

I love what you are doing and it is clearly giving you great results . It just proves that KL can only do so much to maximise flavour development - Then its all up to the extraction or brewing of the coffee .

Wayne
theiguanaoz
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Joined: Tue 15 Sep, 2020 5:01 pm
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Re: Espresso brew pressure - impact on flavours

#1510

Post by theiguanaoz »

Wayne wrote: Wed 23 Sep, 2020 7:50 am Hello theiguanaoz

Thank you so much for the post .. What a discovery . It makes so much sense .

Just 2 questions from my side . what machine are you espressing off that you can adjust pressure ? Can you adjust the pressure while the espresso extraction is happening ?

I started playing with pressure profiling years ago when the Lamarzocco Strada hit the scene . Its amazing what you can do from a flavour perspective .

I learnt about espresso flow dynamics . The first 33% of the espresso I found was super intense . Almost the heart of the espresso . Massive amounts of flavour . Beautiful sweetness and balanced acidity .
Pressure wise - Full 9 - 9.5 bar of pressure for the first 12 - 15 seconds . when I assessed the TDS % its was super high.

Second 33% is a short , sharp and body filled extraction where I came off the pressure over 10 seconds - 9 - 7 - 5 bars . This phase is all about how much body I can draw out .
As the coffee in filter basket increases with intense heat and the puck is now completely saturated , flavour is non existent . It's all about body and bringing balance to the first part .

The last 33% is a 5 to 6 second spill at 2 bars pressure . I don't actually want too much of the tail . It's bitter and the longer you extract , the more intense the bitter aftertaste becomes . You however need that controlled bitterness to help balance the coffee.

The last part of the above is typically the baristas curse . If you get your extraction wrong with too course coffee or not enough in the basket , you end up with the ratio skewing to the bitter end side and it really drowns out the coffee taste through dilution . The same issue exists when extracting an espresso to your usual 30 seconds . By the time the coffee extraction reaches 15 seconds , it is blonde and moving towards an almost translucent colour . The next 15 seconds at 9 bars pressure is all bitter tail ..

I love what you are doing and it is clearly giving you great results . It just proves that KL can only do so much to maximise flavour development - Then its all up to the extraction or brewing of the coffee .

Wayne
Thanks Wayne, that’s very helpful! I use a Crem One (entry level HX version with PID) that has an adjustable OPV behind the removable drip tray. I can change the pressure between shots using a flathead screwdriver and the blind filter, looking a the pump pressure - but it will be constant throughout the shot. I tend to use brew ratios of 1:1.5 for medium to dark roasts, and 1:2 for lighter roasts, sometimes 2.5. This seems to ensure I stop before too much of that bitterness enters the cup. If not, I adjust the recipe for the next shot. The highest end model of the Crem One range has a pressure profiling knob i believe.

I agree with your summation that the KL can only do so much - but for this novice home barista it’s an important outcome because it removes yet another variable I found hard to control, that being the quality of my home roasts. Now that I can easily tame those, the rest as you say is down to how we brew. Plus, I’ve never enjoyed my specialty coffee as much as I do currently, so I’m actually putting that euro machine and grinder setup to good use.

I also find temperature plays a role in aiding extraction - I go to 95c or 96c for lighter roasts, and as low as 92c for really dark ones. Default on my machine was 94c which again seems to be the best place to start when dialling in as most roasters I’ve bought from are roasting for the ‘standard’ temp I find (lowest common denominator at home would be a machine without PID I take it).

My next adventure is to learn cupping. I had a quick go the other day but I’m one of those people who finds it hard to put a number rating next to things. The flavour wheel is fine, I can manage that. If you have any tips or resources to aid with that, I’d be keen to learn more.
nrdlnd
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Re: Espresso brew pressure - impact on flavours

#1517

Post by nrdlnd »

Wayne wrote: Wed 23 Sep, 2020 7:50 am I learnt about espresso flow dynamics . The first 33% of the espresso I found was super intense . Almost the heart of the espresso . Massive amounts of flavour . Beautiful sweetness and balanced acidity .
Pressure wise - Full 9 - 9.5 bar of pressure for the first 12 - 15 seconds . when I assessed the TDS % its was super high.

Second 33% is a short , sharp and body filled extraction where I came off the pressure over 10 seconds - 9 - 7 - 5 bars . This phase is all about how much body I can draw out .
As the coffee in filter basket increases with intense heat and the puck is now completely saturated , flavour is non existent . It's all about body and bringing balance to the first part .

The last 33% is a 5 to 6 second spill at 2 bars pressure . I don't actually want too much of the tail . It's bitter and the longer you extract , the more intense the bitter aftertaste becomes . You however need that controlled bitterness to help balance the coffee.
Thank you for this post! The question about brewing pressure is very interesting! I found this "paper" on the net: https://compoundcoffee.com/experiments/ ... idamo-Guji
Their findings contradicts the first paragraph that TDS is highest at the higher pressure. They found in their experiment that TDS was higher at the lower 8 and 7 Bar pressures compared to 9 Bar pressure. They did also find that it was easier to get consistent results with the lower pressures.

I did also find this: https://climpsonandsons.com/blogs/journ ... r-espresso
They say: In an attempt to conclude, pulling 9 bar espresso shots isn’t necessarily bad, as harshness or imbalance can be offset by grinding coarser. But saying that, 6 bar pressure did obviously produce a much sweeter and less harsh espresso. Theoretically speaking, higher pressure also increases the likeliness of channelling due to the water predominantly rushing through the least dense area of the coffee bed. Lastly, 6 bars also appeared to widen the espresso recipe parameters at which the coffee tasted great when compared with 9 bar. This means that with 6 bars, a few different variations around the perfect recipe were all tasting great, allowing for a much more forgiving set up in a busy cafe environment.

I've had a lot of problems to dial in my espresso machine and to get consistent results. One of the reasons I believe is that the brewing pressure is to high on my machine and that it's easy to get channeling. With a blind it goes up to about 10.5 Bar. I do often have to grind very fine to avoid too short extraction times. I will try to lower the pressure by adjusting the OPV (over pressure valve) to a lower pressure. This is possible to do on my machine and I have instructions on how to do it. I have to go into the machine to do this though. It should have been nice to be able to easily adjust brewing pressure though!
nrdlnd
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Re: Espresso brew pressure - impact on flavours

#1940

Post by nrdlnd »

Late comment!
I did lower the brew pressure om my HX machine to 8 Bar (previously 10.5 Bar with a blind). I can't say that it changed the taste of the espresso in any special way and I haven't made a blind test to compare. What happened though is that now I very seldom get channeling! This is a great advantage for me.
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