for a good couple of months i’ve had a thought in my head that i never got round to testing due to lack of apparatus to record data, so i thought i’d throw out in the open to see if anyone else has thought the same.
Grinding frozen beans gives you colder grinds than grinding below/at room temp beans would, and therefore the temp loss when your brew water contacts the grinds will be larger, and will take longer to get to the equal heat, or close to it. And as far as my knowledge goes it means the brew will extracted unevenly for longer.
So it made me think about heating the grinds up, which in theory will make the temperature loss be smaller, and will shortern the time it takes to reach a temp equilibrium, which lead to a higher and more even extraction.
But as mentioned, never actually tested it out due to lack of logging equipment, and how to heat the grinds up in the first place (hair dryer?).
…curious to see the responses here with respect to heating the grinds before brewing. As an aside with respect to grinding frozen beans, my initial thoughts are that the sudden flood of near boiling water into the portafilter (on ‘frozen’ grinds) may result in a minor decrease of the brewing temperature but this is overcome and quickly re-stabilizes in a fraction of a second as more water passes through.
On the other side, and in addition to heating the grinds, it would be interesting to see and be able to calculate the effect of a room temperature basket vs. a warm basket (ie. just washed vs. just wiped from the grouphead) on extraction + taste [assuming all other parameters (grind, dose, tamp, time, yield, etc.) are the same]. At home, I wash + dry my basket after each shot, but I know this isn’t common practice in a shop setting …not to say it shouldn’t be!
my initial thought was for brewing coffee, but i hadn’t even thought about espresso! i know theres a blog called strivefortone that covers the mythos’ heating elements affect on grind temp on the ‘Low Pressure Rehash’.
Another thought is that if you heat the grinds, would that make the water pass through faster due to more space between the grinds caused by expansion?z
@nico@shawnthacker I’ve actually done some (simplified) calculations on espresso extraction temperature and the impact of grind temperature, which I wrote about on my blog (see here). If you did want to investigate, I think the easiest way to preheat the grinds would be stirring them in a cup that has been pre-heated on the cup warmer (or similar).
Regarding the idea of an even extraction: a seemingly common, but physically impossible goal (for espresso anyway).
The conditions at the top of the puck will always be different to those at the bottom of the puck, which means the rate of extraction (i.e. the transfer of mass from the grinds to the water) will be too. So, unless you run the shot until there is nothing soluble left at all, unevenness is inherent to the process.
Impossibility aside, I’ve also never seen a convincing argument explaining why an even extraction should necessarily produce a better tasting shot.