Does pre-heating a puck on the group head produce more crema? In my never-ending quest to get just a little more crema out of every shot, I've been experimenting with some advice I received from a barista - allow the puck to warm a bit in the porta filter on the group head prior to pre-infusing and pulling.

I have tried this, and I'm still skeptical - I don't really see a difference in the amount of crema that I get. I've tried a few different beans with this experiment:


Illy - Arabica, medium roast
Lavazza Qualità Oro - Also Arabica, medium / blonde roast


While I do get a tad more pressure, I'm not getting any more crema than I usually do. His logic was pretty simple, pre-warming at around the 90 degrees Celsius that the head / portafilter tend to be results in more of the oils in the extraction, hence crema. 

I've let it pre-heat for up to a few minutes with no real change in the pulled shot, with and without pre-infusing. 

Is this just a tall tale? Am I not letting it get hot enough or for long enough? Is Arabica just too gentle of a bean for this to work? The reason I'm trying to get more crema is for a few new deserts I'd like to make, the coffee is still delicious, I just hoped that the experiment would yield more.

Brewing using a Breville Barista Express (manual mode), if it makes any difference.
Well, I've heard a lot of "pro tips" and advice having worked around espresso machines for a few years. And I must say, this one is new. I have never heard of warming the coffee itself. I can't imagine that, at the temperature at which the brew head usually resides, many significant changes are made in just a few moments of warming the coffee.

The closest I've heard to this is that some believe in the opposite. A fellow once told me to leave my spent puck in the portafilter if someone was going to be brewing again shortly. He claimed this helped retain heat in the portafilter. Though the science checks out, the results proved marginal and pretty much just made you the lazy guy using the espresso machine.

So, in closing, I'd say that the effects of warming your coffee are probably negligible, and that you can get more crema more easily through other means (buying better quality coffee, adjusting your brewing variables, etc)