Monolith Conical Grinder and Freezing Coffee

Grinders are one of the keys to exceptional espresso. Discuss them here.
BaristaBob

Postby BaristaBob » Jun 14, 2018, 1:55 pm

Just something I have been wondering about in preparation of receiving my new MonoCon grinder this September (only three months away). My current grinder is a Rancilio Rocky. To get this baby to perform "well" I found through a series of experiments that freezing each dose of beans overnight really enhanced flavor in the cup. So my routine consists of grinding frozen beans, along with RDT and WDT. I'm "satisfied" with the end results, however, I'm hoping to eliminate the freezing step in the grinding process, if possible. So...what do most of you do? Have any of you experimented with room temp vs. frozen bean grinding with the MonoCon and if so what was your flavor experience...better, worse, no difference?
Bob "hello darkness my old friend..."

nuketopia

Postby nuketopia » Jun 14, 2018, 3:49 pm

You can just put the beans in the Monolith at room temperature and make great coffee.

Here's what I've found over the last couple years:

1. Frozen beans will "grind finer". Same beans, same setting, but straight from the freezer will pull a slower shot.
2. Pre-heated beans (125f bean temperature) will "grind looser". Same beans, same settings will pull a faster shot.

Flavors are different with each. Extraction yields, as measured with a refractometer, are higher on the pre-heated beans, especially if you tighten the grind to run the shot at the expected rate.

But perfectly happy with room temp beans. :)

BaristaBob

Postby BaristaBob » replying to nuketopia » Jun 14, 2018, 4:12 pm

Thanks Larry.

I've always wondered about warming beans before grinding. Since many articles discuss that heat can damage or even destroy flavor compounds within the cellular structure of coffee beans my thinking was that you should avoid going in this direction. Some grinders even employ cooling fans. How hot did you warm the beans before grinding?
Bob "hello darkness my old friend..."

dmw010

Postby dmw010 » Jun 14, 2018, 5:02 pm

At least one grinder takes temperature into account. The Mythos One grinder has heating and cooling at the burrs to maintain constant temperature during grinding. The best description I could find quickly is at https://sprudge.com/nuova-simonelli-cli ... 46084.html.

BaristaBob

Postby BaristaBob » Jun 14, 2018, 5:08 pm

nuketopia wrote:You can just put the beans in the Monolith at room temperature and make great coffee.

Here's what I've found over the last couple years:

1. Frozen beans will "grind finer". Same beans, same setting, but straight from the freezer will pull a slower shot.
2. Pre-heated beans (125f bean temperature) will "grind looser". Same beans, same settings will pull a faster shot.



Just re-read your reply...okay, heated to 125F

Through my Rocky (50mm flat burrs @ 1450 rpm), even near 0F beans will end up at 75F out of the grinder (20g in / 18g out in 15 sec.).
Bob "hello darkness my old friend..."

Beewee

Postby Beewee » Jun 14, 2018, 11:06 pm

There's a huge thread from 2015 about using sous vide (vacuum) and heat for espresso: Sous Vide Espresso Extraction-WBC finalist Dawn Chan Kwun Ho

Some of the thinking, experiments, and results are as follows:
- The use of vacuum draws out some of the CO2 from the beans, thereby reducing the amount of carbonic acid created during extraction. This then reduces the acidity in the cup.
- The use of heat before grinding softens the bean structure and allows the grinder to cut the beans more effectively, resulting in less fines and more consistent particle size distribution. This is as opposed to using frozen beans that are more brittle and tend to shatter rather than get cut when they come in contact with the burrs.
- The use of prolonged (more than 4 hours) of heat will degrade the bean quality but a short period of heating of the beans, less than 1 hour, did not have a detrimental effect on the beans.
- Some have tried microwaving the beans before grinding with varying amount of success.
- Heating beans prior to grinding with a conical burr grinder did not appear to provide any benefit whereas heating beans prior to grinding with a high quality flat burr grinder did appear to provide benefit.

nuketopia

Postby nuketopia » Jun 15, 2018, 12:32 pm

I was curious about the Mythos 1 - since it is the only grinder I know of that intentionally heats the beans ahead of the burr. It had such a good reputation that I had to experiment and see what it does. I found that it made for a looser grinder, but it increased the TDS in the cup. (not enough samples to scientifically prove it statistically, but it tended to indicate such. would need lots of carefully controlled samples to establish statistical significance)

But the Monolith produces great coffee from room temp beans.

The Sette 270w does a pretty good job of it too.

gr2020

Postby gr2020 » Jun 15, 2018, 12:58 pm

nuketopia wrote:Here's what I've found over the last couple years:

1. Frozen beans will "grind finer". Same beans, same setting, but straight from the freezer will pull a slower shot.
2. Pre-heated beans (125f bean temperature) will "grind looser". Same beans, same settings will pull a faster shot.


This is interesting. I've consistently find that my shots in the afternoon tend to pour a bit faster than those in the morning, with the same settings on the Monolith.

I live near Denver, and it tends to be cool at night, and warm up during the day. So for me, during the summer, "room temperature" in the cabinet where my coffee is stored is typically around 69-71 degrees in the morning, and ~75 degrees in the afternoon (with air conditioning running). In the winter, mornings might be 64-68 degrees (heater running, but still ramping temperate throughout the house), and 68-70 or so in the afternoon. So in either case, up to a 4-5 degree difference in ambient temperature.

I find shots tend to run maybe 2-3 seconds faster in the afternoon for the same volume, give or take. Not always, but as a general rule, this seems to be fairly typical.

I've always assumed it was a humidity difference (although I don't have any tools to measure this inside). But temperature could be it instead. If it was the metal in the grinder burrs expanding/contracting, I would expect colder parts to contract, and thus making a coarser grind when it's colder, which is opposite to what I see, so this is likely not it.

So I'm thinking perhaps it's the beans themselves being cooler/warmer causing some of the difference.

nuketopia

Postby nuketopia » Jun 16, 2018, 12:19 am

Yeah, the people who designed the Mythos presumed that heat was just causing the gap between burrs to expand - but proved without a doubt that was not what was going on. So they put in a pre-heat chamber in the bean feed so that the beans were warmed and presented to the burr at a very consistent temperature. The prevailing theory is that it increases the volatility of certain compounds in the bean, leading to higher extraction yields.

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aecletec

Postby aecletec » Jun 16, 2018, 1:02 am

Other research has shown that cooling the bean changes its grinding particle distribution. I don't know where the cutoff for this would be in terms of heating. Do you have a source for the volatiles hypothesis?
One thing I do know, however, is that quality focused cafe owners I've talked to disconnect the heating element on their Mythos because it increased their inconsistency (after testing).