I just started wondering, has anyone tried to heat fresh grounds rather than the beans?
It might help answer the question whether something changes in the extraction vs the grind...

[creative nickname] wrote:I checked with a laser thermometer, and I found that my beans were heating more evenly than what you describe. I heat the beans in a small, shallow ceramic dish (the same one I use for weighing out doses), and found that the temperature varied from around 100F to 125F, with most of the beans falling between 110 and 120F. This was for a 16g dose, after 30s of heating at full power.

Good observation - not surprising. I don't know how much variation there is in different beans/roasts regarding moisture levels and the like, but different microwaves will certainly vary.

TomC wrote:I used my IR thermometer and saw somewhat similar variations in temp evenness, so I switched to simply using my plastic roasting sample trays, One dose easily lays flat in one layer and it makes for very easy, no burned hands grabbing and dump right into my grinder.

CrabRangoon wrote:I felt that using a heavy ceramic ramekin was a good choice for microwaving, as the entire dish warms up quite evenly without becoming too hot to handle with bare hands. I tried this a few times and regardless of what my outcome in cup was, it felt quite consistent (I used medium power for 35, 40, and 45 seconds).

Some vessels used to hold beans will be unaffected by the radiation and stay cool, while others will heat up. I don't think there is much reason to believe that there is any significant heat transfer from the vessel to the beans, especially in just a fraction of a minute. Variations in temperature are mainly due to the action of the microwave on the beans, not on the container.

day wrote:I thought the idea was that some coffees were roasted light to preserve character but that resulted in low extraction yields. Therefore heating the beans helped because it allows a percentage or so better extraction. Which would mean that if you were already reaching your "ideal" extraction parameters then that coffee would not be one of those that would benefit from the process because you would no longer be that ideal or target number? It does seem to make sense that of a bean is already roasted so that it allows 21% yields in an espresso shot "out of the box" that the bean would inherently have more toasty characters than a bean that CAN NOT reach 21%, and that therefore one would expect an increased extraction % at a given grind would increase that toasty element, i suppose.

Hehe...for example, you probably wouldn't want to increase extraction yields on charbucks beans nor would you want to in a bean that didnt have enough acidity and floral notes to withstand it. Apparently a light roasted Geisha might just have the requirements to satisfy the NEED for increased extraction while having the chomps to shine despite somewhat muted brightness?

In my case, my beans were very light-roasted (12-12.3% WL, dropped ~15 F past 1Cs). I think a properly roasted city roast should be soluble as drip coffee. And in that case, there's little benefit with heating.

I do think this method seems more useful for espresso, where my lightest drip roasts are adequately but not impressively soluble. It can get me from, say, 19.5% or 20.0% EY to 20.5% or 21.0%. I'll keep trying it in that setting.

Trimethylpurine wrote:Addressing the bolded parts from your questions....

No blind testing whatsoever in this thread.

h

Actually there was...maybe a better observation would be "extensive" blind testing hasn't yet been completed.


I didn't see anyone yet mention (other than speculation) about how the grind is being changed by heat. Trying out this method, my grounds seem much more fluffy. Or put another way, if before 15g would fill the basket to the rim, now it's overfilled. Using same coffee and grind setting. My guess is based on this, that grind particle shape is somehow being changed with a different temperature going into it. Maybe the Mythos was onto something...

Would it be possible that the heating process and freezing process both affect the coffee bean in a similar fashion? That is, both processes help break down / soften the bean pre-grinding?

Interesting and related:

https://colonnaandsmalls.wordpress.com/ ... g-puzzles/

Very interesting. But a bit confusing.

I buy the argument that colder beans produce more fines. I also buy the argument that you can't grind finer to counter the increase in flow rate when the grinder warms the beans because this will change the particle size distribution and thus the extraction.

But while it may be best not to adjust the grinder as the day wears on, I don't buy the conclusion that a faster flow rate doesn't affect extraction. I think some refractometer measurements are in order!

Isn't that the story behind that new heated grinder?

Peppersass wrote:V...
But while it may be best not to adjust the grinder as the day wears on, I don't buy the conclusion that a faster flow rate doesn't affect extraction. I think some refractometer measurements are in order!

It's that the grinds being hotter are more soluble and thus the faster flow rate is countered to some degree. If it's tit for tat is left unknown.

There has been both dancing around the most plausible explanation for this taste improvement and direct mention of it.

TomC wrote:I'm just too curious about the effects this method has on how beans grind in general.

bigred23 wrote:I have to believe the dominant effect here is that we're effectively altering the grind size distribution, and reducing fines due to more pliable beans. At these low temps, I wouldn't think we're affecting additional changes to the bean chemistry beyond what was achieved during roasting. Thoughts?

bigred23 wrote:sous vide in espresso prep...wild. Is heating the beans affecting the pliability of the bean structure, and thus changing how the bean is ground i.e. less fines? It would be interesting to do a quick test with a sieve to determine any difference in fines production between heated and non-heated beans

Right on, Paul. It took Marshall H's link contribution at the end of this thread to support this.
If there is any chemistry here, it seems to lie not in additional reactions but in the physical chemistry regarding fewer undesirable extracted moieties due to more uniform grind.

There is the link previously offered by Mrboots2u:
http://grindscience.com/2015/03/heating ... ng-part-1/
...which contains the text: "From Maxwell and Chris' explanations we could be seeing the beans becoming more pliable as they warm, this results in a much more even breakup when ground. This is really interesting and something to investigate further..." (validated by subsequent posts by its author, Spencer Webb)

Peppersass wrote:I buy the argument that colder beans produce more fines. I also buy the argument that you can't grind finer to counter the increase in flow rate when the grinder warms the beans because this will change the particle size distribution and thus the extraction.

another_jim wrote:If the difference is simply one of gross extraction, as some suggest, the technique would simply be a an alternative to making dose/grind changes. Most of these recent and difficult to test claims do not appear to be about gross extraction, but about what may be called extraction balance -- is the proportion of lighter molecular and heavier molecular weight chemicals in the cup affected

Exactly. Extraction balance: 'grooming' particle size for the exposure to time/temperature/pressure to eliminate unwanted extractions.

NoStream wrote:I do think this method seems more useful for espresso, where my lightest drip roasts are adequately but not impressively soluble. It can get me from, say, 19.5% or 20.0% EY to 20.5% or 21.0%. I'll keep trying it in that setting.

yakster wrote:Is the thinking on this that it'll have less impact on darker roasts?

Why does this seem to benefit lighter roasts the most? Is it because they are more brittle than darker roasts and more prone to shatter without this extra treatment?

NoStream wrote:With sous vide at least, the beans literally couldn't exceed the SV temp setting, and the effect is evident. So that would suggest that we aren't merely developing the beans.
Regarding brittleness, I think the microwave might be unique in that regard.

Perhaps the microwave might not be unique, this is probably not purely about the movement of water, but Nostream was the first to mention 'brittleness', which quite possible could be the parameter that we are messing with, or at least implying in our discussions..

rooster81 wrote:Would it be possible that the heating process and freezing process both affect the coffee bean in a similar fashion? That is, both processes help break down / soften the bean pre-grinding?

The impact of freezing is beside the point of this thread but softening the bean seems to be the operative concept.

[creative nickname] wrote:Based on this single test (which is an admittedly weak basis for drawing any firm conclusions), the main impact of this seems to be something that happens to the beans when re-heated, rather than merely an increased extraction arising from brewing with warmer grounds.

IMAWriter wrote:So, the heat generated can be deleterious, but the beans themselves pre-heated isn't?

The heat benefits only the breakup of the whole beans; perhaps it remains deleterious if it works on the grind and especially on the unwanted fines.

NoStream wrote:The amount and time of heat is not enough to cause chemical change.

Agreed. No chemcal reaction, just preparing the bean for more 'controlled' (less random) fracture.

Since the effect is only on the whole (or coarser preliminary fragments of) bean, this may explain why the benefit might be different for flat versus conical grinders, if truly present.

EspressoForge wrote:I didn't see anyone yet mention (other than speculation) about how the grind is being changed by heat. ... My guess is based on this, that grind particle shape is somehow being changed with a different temperature going into it. Maybe the Mythos was onto something...

Your speculation is just as good as mine. Check below to see the colonnaandsmalls link, which offers more support of what has been speculation up to this point. Again, preparing the bean seems to be the thing. I remain skeptical about the benefits of a heated collar. The temperature duration seems too critical to be left to the vagaries of bulk passage through a heated collar; and once the bean is ground (fractured/sliced), exposing the grinds, the heated burrs would not benefit them, according to the themes in this post.

And, finally, after the thread has developed for quite some time, I am indebted to endlesscycles to providing this link that appears to clarify and underscore the point that either has been implied or stated outright: that what is being done here is what the grinder manufacturers have been and continue to attempt, namely, to increase the uniformity of the grind.

endlesscycles wrote:Interesting and related:

https://colonnaandsmalls.wordpress.com/ ... g-puzzles/

Postscript: my point is that decreasing shattering for more grind uniformity is the main process at work here; I am not claiming that there can be no other processes at work, only that I think that they are secondary, if present.

If someone wants to simultaneously interject other variables such as flow rate and surface area (how about temperature gradient down the puck depth?) and then complain that the system is too complicated to understand, or is too full of contradictions, they are free to do so, but this explanation is the 'Occam's razor' that presented itself to me.

BT