Posts Tagged ‘brew temperature’

Talking About Pressure Profiling

Sunday, January 17th, 2010


Is it me or is everyone else a little surprised at the lack of discussion of pressure profiling?

Most of the interesting discussion, if not just about all of it, has been over at home barista where various people are building pressure profiling units for their one group machines.  Still much of that discussion remains more about how to build it, than about desirable profiles.

Pressure profiling is undoubtedly going to become more readily available.  Though the capacities of the Slayer, the Strada and Cimbali’s new machine are all different, they are all chasing the ability to manipulate pump pressure to improve espresso.  A lot of this desire comes from the profile of espresso produced by lever machines, which have a very different pressure profile compared to a pump driven machine.

Perhaps I shouldn’t be surprised, given my own experiences with pressure profiling.  I was asked, a little while back, about why I hadn’t posted anything about it and I thought I would take this opportunity to explain:

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Posted in Espresso, Opinion | 31 Comments »

Brew temperature

Tuesday, October 27th, 2009
temp2

This, shockingly enough, isn’t about espresso.  It is about brewed coffee, and the fact that brew temperature is completely wrecking my head.  We talk a lot about brew temperature but what we are really talking about is water delivery temperature.

I love my Uber boiler, I love the control and the delivery temp stability.  With this, however, has come the painful and embarrassing realisation that it doesn’t matter.  Alright, that is perhaps an overstatement – temperature has massive influence on the quality of the brew, that is undeniable.  I may love the control of the Uber, but having a consistent and controllable temperature really just shifts the problem from the exit spout to the vessel underneath.

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Posted in coffee brewing, Opinion | 23 Comments »

WBC Machine Testing – Temperature Testing

Sunday, January 13th, 2008

Vancouver is a lovely city, but it seems it likes to rain. So we’ve all been cooped up inside testing the six machines submitted (I am glad I am not the one paying to run 6 three groups all day!)

People probably want to know how this works and I will try and explain, but I warn you it isn’t massively exciting. As a tester I have no idea how the machines performed. The Scace devices run straight into a datalogger and then into a laptop which is kept out of view. I will never get to see the data, unless a manufacturer chooses to publish. Also a manufacturer will only see their data and not the other machines.

The testing protocol is pretty simple. Each round consists of 14 shots pulled at varying intervals, with the device removed at certain points to simulate grinding, as well as knocking out the puck and flushing. Each machine has four rounds of testing: middle group only, middle group and steaming, 1st and 3rd group only and 1st and 3rd gorup with steaming. With the latter rounds two people worked the machine, even though it was replicating one barista using this. We did this to make sure we could be as consistent as possible in the collection of data across machines. With the steaming we had tested each machine to see the time it took to steam 10oz of milk up to 60C, and then that time was used during the testing.

It hasn’t been the most fascinating testing to watch – every manufacturer was present with a technician during the testing and I think the constant counting down each action, second by second, was close to driving everyone a little crazy!

I think the testing has been very fair, I think the protocols are very good (though I don’t think anyone is claiming that it is beyond improvement). If anyone has any questions I will try and answer them though if you have issues or complaints I am probably the wrong person to speak to. Everyone seems very happy with the fairness of it, which is good.

Next up is grinders which will take a while, and I will write a bit more about that after we have done it.

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Posted in News | 16 Comments »

Brew Temperature and the Chemex

Friday, November 9th, 2007

I remember reading early in my coffee days that someone had done an experiment where they had compared heat loss in porcelain espresso cups of different thicknesses and found that the heat retention of the porcelain didn’t much matter because all the heat went out of the top anyway. Like a lot of what I read on the internet at the stage I didn’t question it, didn’t want to see data but instead found it interesting, tucked it into its little trivia box in the brain and moved along.

After some comments in the thread about using scales to brew my Chemex on brew temperature I decided to perform a few rounds of experiments. Simple really, I just placed a probe (K-type, not ideal but it will do) into the bed of coffee, poured over the water and waited to see what would happen. The first test gae me an unexpected result.

Brew temperature of a Chemex

Brew temperature of a Chemex

What I expected was a steady decline in temperature during the extraction, and over a couple of minutes losing a fair few degrees, due to the area of steeping coffee being quite large. When the probe was in at the top of the brew the total heat loss was about 2C. Not much at all. What was interesting also was the temperature gradient throughout the liquid. At the start it was a couple of degrees from the top of the brew to the point of the filter cone and over brewing that stretched out to about 4 or 5C.

I’ve only done this experiment a few times so if you have the kit and a few extra minutes to spare I’d love to see it replicated – the coffee coming out isn’t much affected by the probe so it isn’t a wasted cup in the morning.

To completely and utterly hypothesize – it seems the floating crust of grounds does wonders for insulation, possibly with the help of CO2. In the next round I’d be tempted to stir and skim like a cupping bowl to see if this accelerates the cooling.

Thoughts anyone?

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Posted in Coffee, Food Chemistry, Opinion | 12 Comments »