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The wizardry of moisture

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On my quest to tame charcoal, I am continually running into moisture and realizing they are part of the same ecosystem, and one cannot be conquered without understanding the other.

Everyone knows the cheeseburger skillet trick. The one where the burger is ready to come off, but you forgot to put the cheese on. The solution is to drop a small amount of water into the skillet and immediately put the lid on. The moisture, trapped, steals heat from the bottom of the pan, boils, turns to steam, and transfers heat to the cheese which promptly melts in seconds. Voila!

Moisture is the great temperature equalizer. A dry grill will have more hot spots and cool spots than a moist grill.

Ever notice (perhaps not with a heat soaked KK!) that a fully stable Kamado Joe will have a temperature drop when you put meat on the grill? I will ignorethe heat lost to opening the lid, and calling it even for the additional oxygen added. Firstly, the equilibrium is slightly thrown off by adding a weight of room temperature meat. This is a vapid and beginners explanation though. My 340lbs Big Joe at a temp of 275f shouldn't have a temperature drop of more than a degree per pound of meat I add, if it were a simple balance the temperatures equation. Secondly, there is the issue of wet/dry equilibrium. A "dry" has a tenancy to be hotter on top, cooler on bottom. Try touching underneath the ceramic, the bottom of the grill. Very cool.

This has led me to recognize there is a dry heat equilibrium, and a wet heat equilibrium. A dry heat equilibrium of 275f will have energy used to warm meat (of no consequence), and to evaporate moisture (of large consequence). As most of us know, it takes 5x the energy to evaporate a ml/gram of water than it does to raise its temperature from frozen to boiling. This energy used to evaporate water will provide for a lower grill temperature with the same airflow rate to the charcoal. This is the reason a grill will lose temperature when you add meat, and then slowly climb over the coarse of the cook as moisture leaves. The less energy expended evaporating moisture, the higher the equilibrium temp of the grill.  This applies more so if the meat added has a large wet surface area, like chicken wings. Less so if the meat has a small surface area to volume, like a roast.

Additionally, adding moisture to a dry equal grill will lower the dome temperature and grate temperature because just like the cheeseburger, the moisture has the ability to steal heat from the top of the grill and give it to the bottom of the grill.

Which brings me largely to the end of my knowledge of moisture, but opens up many more questions.

For example, although the temperature of the grill may be lower and the relative humidity higher, does it really matter? "The temperature feels hotter than it actually is with the presence of more humidity in the air". Does this translate to a BBQ and Meat, or is it only relevant to human skin?

Will the moisture help transfer heat faster from the air to the meat? Does this energy that evaporated water (not destroyed, but repurposed), make up for the drop in temperature when it comes to cooking time? is it a "wash" as they say?

If I hold a dome temperature of 275f, will keeping a lower or high RH make the cooking time shorter or longer? or does it matter?

Next I have many questions about moisture, RH, and browning. and a few crackpot theories.

I have come to the conclusion that certain foods need to be cooked above a certain temperature, and others don't. Bacon is one such food. In this illustrative example, I cook bacon single layered on my grill at 225f. Its too salty to eat because the moisture has evaporated, rather than dripped off the bacon. When evaporating water, the salt remains, and the bacon is too salty. When cooking faster, some grease drips away, taking salt with it, leaving the bacon edible. The obvious solution is to cook it like a roast, in a slab, for tenderness, then grill at the end.

As the temperature increases, there is less need to worry about this phenomena, as the faster heating = faster protein twisting expelling water = drippage.

I'm wondering if this has anything to do with the beloved temperature of 275f being the transition point from Smoking to BBQing? or more to the point, that perfect temperature that is hot enough to build a crust, and low enough to tenderize meat. I suspect perhaps. Some well respected people I know will favor tenderization and drop the temp to 250 and compensate with a sear at the end.

Browning will only happen above a certain temperature, and more efficiently at even higher temperatures. Water will not rise above a temperature of 212f, but any excess energy added when at this temperature is instantly used to vaporize water. Water will still vaporize at a lower temperature, but slower.

The way a french fry gets its brown, crispy outer shell and pillowy soft inside is my starting point for trying to figure out how a roast on a BBQ gets its browning, in relation to moisture and temperature. With a french fry, the surface area to volume and moisture content are key. When the french fry is dropped in hot oil and starts to warm, it shrinks and expells moisture. This moisture, upon contact with hot grease, does a phase transition from liquid to gas whereby that 5x energy we talked about earlier is released as a giant expansion, or explosion if you will. Water, in the form of gas, takes up 5500x more space!!!!!! and this happens almost instantly. This is what you see bubbling up from a deep fryer, steam. It only seems impossible and endless, but given enough time the moisture in the food in the deep fryer will run out, the bubbling will stop, and the oil is still hot as F, even though motionless. (always beware the still oil! it is potentially much much much hotter than bubbling oil, whereby converting water to gas keeps the temperature lower)

Back to the french fry, its this rapid expansion of moisture is constantly happening on the very outside of the french fry that makes a crispy fry. Every explosion near the boundary of fry and oil tears little holes in the potato (i imagine it looks like dead skin under a microscope!), allowing the oil to penetrate further into the french fry, even as the moisture is billowing out. It is the hot temperature of the oil that causes the browning, but the expansion of gases that allows the crust to expand inwards toward the center of the french fry.

To little moisture to begin with, and you have a crisp but dry fry. Too much moisture to begin with, and the inside isn't pillowy soft, but rather starchy hard.

Come to think of it, a brisket at 225f has a great crust! Even a brisket at 215f. But 200? Not that Im aware of. I have always thought that 225f was a thing because its a good minimum for food safety. Lately, I have been tending to think of it as a temperature that is near the phase transition of water into a gaseous state, which may also overlap with food safety. More importantly, my intuition tells me that a good crust requires an ever so thin outer layer that approaches or exceeds the boiling point of water. My intuition tells me that moisture prevents browning because the energy is being used to evaporate water, not brown meat. Even if that isn't true, moisture still keeps the temperature down, and makes browning less efficient. It further tells me that there is a transition zone on the edge of meat where the temperature going from meat temperature to dome temperature is where the crust is built. It also tells me that this layer doesn't exist if there is an unpenetrable wall of mositure in the form of water on the outside of the meat, and that this is why nobody cooks a brisket at 190f. Because the moisture not evaporating and not rapidly expanding fails to create that jagged, sharp, crevasse filled landscape that allows for a larger temperature transition, and by extension a hotter outer layer where the browning is happening.

Am I on the right track?

In what other ways can I see and utilize moisture and temperature in the service of better cooks?

Is there some kind of special phase transition or other energy thing that happens around 275f? Or is that temperature just a good balance cooking the meat slow enough to be tender, but hot enough to operate higher in the Maillard heat/efficiency curve?

or is that just a made up temperature that signifies the divide between Smoking and BBQing?

Any thoughts are appreciated, even debunking my entire parts of my post would make me smarter.




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Between you and @Syzygies, I don't know who makes my brain hurt more?? :morons:

Evaporative Cooling, Heat of Vaporization, Departure from Nucleate Boiling - You guys are dispelling the idea that making good BBQ, especially on a KK, is NOT Rocket Science! 🚀

Let's pose the question in a less academic way - how does one achieve the best crust/bark on: 1) a high temperature sear, like a steak; and 2) a low & slow cook, like a brisket or pork butt? Are the best techniques the same or are they different? For example, to get a good sear, one pats the steak with a paper towel to remove excess moisture and you want a very high surface temperature (for the geeks - less evaporative cooling and better heat transfer - more Maillard reaction); but on the brisket/butt, we spritz the surface with moisture to promote smoke retention (more evaporative cooling and sticky surface - better particulate adhesion) and we cook at a much lower temperature to render fats and collagen breakdown (tenderizing). Different cuts of meat - different techniques to achieve the desired results.

Does our cooking improve if we know the "why?" these techniques work or are we just content to rely upon "tribal knowledge" to achieve the desired results? I leave that answer up to the individual - this Forum can accommodate both! The beauty of this community! :occasion5:

Edited by tony b
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You mentioned that when adding a cut of room temp meat to an already established grill the temp drop is proportional to the mass of the unit and volume of space. Placing a cold piece of meat on the same grill will give a greater heat loss, retain it's moisture longer and that is what I try to achieve without changing the settings. This allows the piece to remain in the smoke longer when smoking large pieces. Working in additional moisture as a spritz and sealing the meat with a tallow to prevent moisture loss are contributors. There is always a means to an end, it's called technique. I practice mine with the tools I have and the KK does quite a bit of the problem solving, so that I don't have to.

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On 2/3/2022 at 4:09 PM, Tyrus said:

You mentioned that when adding a cut of room temp meat to an already established grill the temp drop is proportional to the mass of the unit and volume of space. Placing a cold piece of meat on the same grill will give a greater heat loss, retain it's moisture longer and that is what I try to achieve without changing the settings. This allows the piece to remain in the smoke longer when smoking large pieces. Working in additional moisture as a spritz and sealing the meat with a tallow to prevent moisture loss are contributors. There is always a means to an end, it's called technique. I practice mine with the tools I have and the KK does quite a bit of the problem solving, so that I don't have to.

Yes, I see how the temperature drop when adding cold vs warm meat is not relevant when there are hundreds of pounds of mass, and how a colder cut absorbs more smoke flavor. Good point.

More interesting to me is "sealing the meat with Tallow". Its almost like a hybrid "frying" technique, where the evaporative cooling aspect is throttled and instead the water expanding in volume to steam forces its way through a layer of hot fat. As this steam bubble expands and then pops, the outer oil layer of the bubble can get really hot because its so thin. It browns, and then pops. Like mozzarella on a pizza. Its the bubbles and a thin layer of oil at a high temperature that create the browning where without bubbles that high temperature reaction wouldn't occur.

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@tony bYou mentioned in another thread that "a 50F difference between dome and main grate temperature is "normal" for a KK, especially early in the heatup process. With a long enough cook (hours) they will tend to equilibrate a bit closer, typically within 20-30F."

This is true of many cookers, very easily explained and goes to the heart of the relationship between heat and moisture.

Temperature is a fight between the firebox and the moisture.

The Firebox will stay relatively stable on a komodo. Lets assume the energy input stays the exact same throughout the cook (No drippings damping it, no flue rate changes due to temperature changes, etc).

Heat rises. Therefore the top of the Kamado is hotter than the bottom. After adding moisture (meat), the energy input remains the same but some of that energy will be used to evaporate water. This will lower the stable average temperature of the Komodo (.vs dry stable temperature) as some of the energy is used to evaporate water. This evaporated water will then immediately get to work circulating in the komodo and facilitating the transfer of heat in a more equal way. It will lower the Dome temperature and raise the grate temperature as well as the mid and lower sections of the heavy komodo. This will also lower the APPEARANCE of total energy in the Komodo if the user is only using the Dome temperature as a guide. The total energy stored in the komodo steel/ceramic will stay the same (relatively), but be more evenly distributed. It will also allow the Komodo to hold more heat energy as the moisture allows the bottom half of the komodo to hold more heat energy.

As you have stated, as the cook goes on, the grill temp and dome temp converge. This is the work of moisture. The reverse is also true. As a piece of meat loses moisture and loses moisture at a slower rate, the temperature of the Kamado will rise. The two-fold reasons are the same but in reverse. As the relative humidity drops, heat rises without the counterbalance of being conveyed back down by hot wet air. As the moisture disappears, the firebox is no longer wasting energy supporting water evaporation, so there is excess energy again to raise the temperature and create a higher equilibrium.

(I wonder if the "stable dry temp" before adding meat is the same as the stable dry temp after allowing a piece of meat to completely lose its moisture and the internal temperature to rise to stability with the grill???? 350F roast please, lol)

As a thought experiment, carry this to the extreme and replace wet air with wet water. The top and bottom of the grill would share the exact same temperature, just as the temperature of bathwater will not vary by more than a degree or two in a bathtub.

Anyway, one of the things I have started doing is adding a small dish of boiling water to my Kamado at startup, even if only a few ounces. This will allow the ceramic of my Kamado Joe to hold more energy and achieve wet stability faster. It also negates the temperature differencial between the dome and grate before the meat goes on the grill.

No more guesswork. Pre-Add moisture, get more useful temperature information from the existing probes.

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