Ideal crema is dark, light, or golden? - Page 2

September 8th, 2006, 2:23 pm

UPDATE: To keep the discussion flow together, I've merged this thread with your previous one. If it turns out to be a bad idea, I'll split them later. Thanks, Dan

i just got a used Gaggia classic, but my espresso is far from even looking like, or tasting properly..
i just learned that hot water equals dark crema, and colder water equals cream or lighter colored crema. I checked water temp using a milk-thermometer and what i got was 65 degrees Celsius... What's the deal? did i just buy some crap or what??
im a poor student, thats why the economy buying..

help please

#12: Post by **King Seven** » September 8th, 2006, 5:13 pm

Your milk thermometer is unlikely to be very accurate.

Some questions - what coffee are you using? how fresh is it? What is your shot time and for what shot volume? How long are you leaving the machine to warm up before using it?

#13: Post by **krus** » October 4th, 2006, 7:28 am

When brew temp is held constant throughout the shot with less than 1 degree variation, that is when you'll notice the redder crema develop. This is thought to be the sign of a really good extraction. Some machines aren't capable of this degree of stability. Most measurements I've taken on smaller heat exchange machines show a variation of 2-4 degrees from the start of the shot to the end. Even with commercial machines, it's not always possible to achieve this degree of stability due to several factors. It sure is beautiful to look at.

#14: Post by **cannonfodder** » October 4th, 2006, 5:08 pm

Given some practice, you can get there.

Well, that is actually from my two group, but this is from my modified Isomac. I added a HX preheat loop.

#15: Post by **King Seven** » October 4th, 2006, 6:18 pm

krus wrote:When brew temp is held constant throughout the shot with less than 1 degree variation, that is when you'll notice the redder crema develop. This is thought to be the sign of a really good extraction. Some machines aren't capable of this degree of stability. Most measurements I've taken on smaller heat exchange machines show a variation of 2-4 degrees from the start of the shot to the end. Even with commercial machines, it's not always possible to achieve this degree of stability due to several factors. It sure is beautiful to look at.

I just don't see the science behind this claim - that somehow a stable temperature changes the colour of the coffee liquid to a more reddish hue. I've heard it many times, and obviously read it in Schomer's writings.

In truth I could make no claims for the stability of this machine (I just haven't tested it) but is this red enough for you?

#16: Post by **cannonfodder** » October 4th, 2006, 7:07 pm

I wonder how much a plane ticket to London is.

#17: Post by **cannonfodder** » October 4th, 2006, 7:43 pm

In retrospect, I find that the color of the crema is influenced more by the blend contents than machine temperature. For a sure fire brick red crema pull some SO shots with Yemen.

#18: Post by HB » October 4th, 2006, 7:43 pm

King Seven wrote:I just don't see the science behind this claim - that somehow a stable temperature changes the colour of the coffee liquid to a more reddish hue.

I can readily agree that delivering stable ("flat line") temperatures increases reproducibility, which increases the likelihood of an exceptional espresso simply by eliminating a source of variance. But I remain unconvinced that one temperature profile is superior to another, not only because of the lack of empirical evidence, but it doesn't even make intuitive sense. Consider the measurements below:

Cimbali Junior - puck top and bottom temperatures (more)

The temperature gradient from top-to-bottom doesn't close until the final moments of the extraction. Evidently the different coffee layers are subjected to a range of temperatures throughout the extraction; it's our hope that this concert of extraction temperatures delivers the desired flavor profile.

Allow me to digress...

I wonder, if one measured the temperature mid-puck between the flattest flat temperature profile and the humpiest humped profile, would the plotted differences be obvious? Are we in reality dealing with such small differences that crude measurements are red herrings? I'm reminded of the news story about the chimp genome project. Perhaps the answer to unlocking godshots is the same as the answer to the separation / similarity of chimp and man - just a few minuscule but critical differences.

Let's take a look at the temperature profile of the Elektra Semicasa Automatica:

Jim commented in his writeup:

another_jim wrote:However, the Semiautomatica's espresso prowess presented a problem while researching this review. By the standards of most US espresso experts and by my experience with espresso machines, the Elektra should make mediocre shots, not glorious ones. The car versus motorcycle analogy applies--in trying to explain why the shots are great, I feel like a four wheel car expert trying to explain just how a two wheel motorcycle can stay balanced. There's a very basic principle of espresso extraction I'm just not getting.

This confirmed something that I've suspected for a long time: The more I learn, the less I know.

#19: Post by **King Seven** » October 5th, 2006, 10:15 am

I think repeatability is always the key with brew temp. I still don't know enough about profiles to stake myself to flat line or any other style of brewing. But as long as the kit does it time and again then that is just one less headache when you are chasing a shot around, trying to capture the taste you are after.

Roast colour has a massive amount to do with the colour of the pour, as of course does temp and flow rate. I just can't accept blindly that flat line temps change the colour of the brewed coffee above and beyond any other extraction.

#20: Post by **maze400** » February 14th, 2008, 9:50 am

I thought the crema was influenced more by tamp pressure or grams of coffee used?