Ladies wanting an A in the class please see the professor after class!! lol....and that concludes today's class on thermal dynamics. Thank you all for coming. Please tip your waitstaff.
(Applause)
Ladies wanting an A in the class please see the professor after class!! lol....and that concludes today's class on thermal dynamics. Thank you all for coming. Please tip your waitstaff.
(Applause)
Would love to, but that requires you to have a degree in Spectroscopy or we are going to be here for a long time. As far as amylase and Maillard, just look em up. You will be surprised what you learn doing a little research to educate yourself on something someone said. Then ask questions if you don't understand something.
But basically all cooking is thermodynamics. More specifically the exchange of energy in the infrared spectrum. Everything has a resonant frequency.
To "see it"
Watch this video of Galloping Gertie
This is an example of an oscillator going into a resonance mode. Here the wind represents the heat (infrared wave of your cooking source) and the bridge represents the meat you are cooking.
As you watch the amplitude of the wave (the bridge bucking harder and higher) you will see a close up of the cable (looks like a pipe line but it is actually the casing of the bridges suspension cables) moving in a countable pendulum pattern, (This is the frequency, in this case very low frequency) as the wind (your heat source) adds energy you watch the bridge rise and fall harder and harder. All resonance oscillators gain in amplitude if you add more power. The bridge is shifting the energy from side to side. Finally you see complete mechanical failure of the steel when the amplitude exceeds the strength of the steel. Causing the energy to be released in a violent mechanical failure.
That is an oscillator. Much much much faster the water inside you meat is doing the same thing. If one could tune the wind to a specific speed the bridge would oscillate at the same rate forever if the loss matched the energy the wind was putting into it. This is what happens with a water activity stall when resonance is reached. (This is what the stall is, nothing magic, just science.) In most case the energy coming into the meat is equal to the heat loss leaving the meat and the cooker happens to be adding and losing the same amount of heat. Adjustments will change this, opening the damper will cool the meat (bad) increasing the temperature will start a new resonance pattern (what we would do in the Southern Pride smoker if we stalled as we know the stall is not magical but a pain since we have to serve on time.) Or you could disturb the oscillator by flipping it with a good squashing, or stabbing it with a fork. (if the bridge had steel added to it the amplitude of the wave would change.) Anyway point is a stall is nothing...... you don't have to wait just crank the heat for half an hour or so, or stab the meat or flip the meat... but don't just wait there, backyard lore says oh you just have to wait it out. That is BS spread by people that subscribe to magic, not science. Kill the stall and move on.
Change the function of the oscillator stops the stall. Most commonly people will watch a stall for a long time thinking it is some kind of magical moment. Stab the crap out of it with a fork, or pull it and mash on it a little and you can skip the stall. In the commercial world this is no we will feed you tomorrow sometime since the meat stalled, there is get it done on time. So we don't wait for a stall to stop, we either stab it or kick the heat up from 250 to 325 for about an hour and it is over. In the backyard realm there is reverence for the stall, but it is just since and a pain in the butt!
If you pick up a college text on thermal dynamics you will become a much better cook IMO. Even if you just read the beginning stuff on energy transfer.
Been a chef for 35 years now, started as one, been a practicing engineer for 28 years now. One pays the bills one relieves the stress! Cooking relieves the stress and has lots of interesting science in it.
No... things like chicken or lean cuts wont stall. Usually the stall occurs in large cuts containing fat and connective tissue.This is good reading material. Will every piece of meat stall?
I'm extremely skeptical. I'm going to side with those who say the stall is caused by evaporative cooling.
It's among the compliance guidelines for some pathogen lethality treatments because wet-bulb temperature is a more accurate measurement of product surface temperature.
~Martin
OK my head is spinning after reading the rest of this.....
So if I understand what I have read (not saying I do). Stall is bad and should be destroyed at all cost and the best way to destroy it is to change something by either moving it, stabbing it or adjusting the temps...... but what about the "Texas Crutch" of wrapping the meat???? does that fall into changing the rhythm of the pattern???.....I am not a big fan of stabbing meat because it releases the natural juices.....but I am game to try new things.........
But it sounds like some of the old school Chef's I have worked for were on to something without even knowing it......they always told me if what I am doing is not getting the results I want, then change something the temp, position or even the oven if needed......
Great info guys....
What do you think about smoking at wet-bulb temperature and is wet bulb temperature a good indication of meat surface temperature.?
~Martin
Wet bulb is not a good indicator of the meat surface temperature.
I thought the stall was due to evaporative cooling?
~Martin
No it is not.
Wrapping changes the Water Activity though you can see a stall continue occasionally because the wrap can act as a artificial bark. Changing temp works real well getting up toward 325 F usually kicks it off.
Stabbing always works. But you can lose moisture from the meat. I pan so it does not affect what I am doing.
Please clarify with your USDA reference. That is the one I will read.I sure would like to get to the bottom of this.
If the physicists, meat and food scientists as well as the USDA are all wrong, I want to know.
"Because moisture is evaporating from the product surface during cooking, the surface of the product acts much like a wet-bulb sock. Evaporative cooling of the product surface keeps the surface temperature at or near the oven wet-bulb temperature for much of the cooking process. Since the oven wet-bulb temperature has a strong influence on the product surface temperature, it also has a strong influence on the surface-to-core temperature difference that determines product heating rates and cooking times. For this reason, the oven wet-bulb temperature essentially controls the product heating rate for much of the cooking process, and is a critically important heat transfer variable."
"During the wet-surface phase of a process, the product behaves as though it is being heated in a water bath that is at the wet-bulb temperature. Any change in the wet-bulb temperature will have an almost immediate impact on the product surface temperature. As long as the product surface is completely covered with a thin layer of moisture, the wet-bulb temperature essentially controls the product surface temperature and heating rate, while the dry-bulb temperature has little or no effect."
"The higher surface temperature increased the surface-to-core temperature difference, and as a result, the product-heating rate for this process was faster than it would have been had the surface stayed wet. If the product surface had stayed wet throughout the process, the constant rate of evaporative cooling would have caused the surface temperature to stay at the wet-bulb temperature for the entire process, resulting in a smaller surface-to-core temperature difference and a longer cooking time."
"Of course, an easy way to increase the heating rate for this process would have been to increase the wet-bulb temperature. This would have resulted in an immediate increase in the surface temperature and the surface-to-core temperature difference, thus creating a faster heating rate. An increase in the dry-bulb temperature would have also eventually increased the surface temperature and the heating rate. But because it would have taken time to dry the product surface and allow the surface temperature to increase above the wet-bulb temperature, the effect would not have been as immediate as an increase in the wet-bulb temperature."
Source: http://www.alkar.com/technical_reports/cooking_truth.html
~Martin
Please clarify with your USDA reference. That is the one I will read.
The stall is not caused by evaporative cooling. It is caused by temperature and water activity equilibrium.
Where I tell you No wet bulb is not a good indicator of the temperature the meat sees. I am speaking of smoker cookers. Were radient infrared is as big part of the process as the humidity.
The reference you listed is a cooking equipment company's sales information it contains no scientific data for reference. It is marketing information presented as science and while based in scientific principal and does apply in certain cooking apparatus it by no means an industry standard. Though it is useful it it gets you to buy their equipment. And does follow principals I have explained, such as increasing humidity increases water activity. Though it tries to sell it as magic their process equipment can do... but really placing a bowl of water in a standard oven will also do it. Since the partial pressure of water causes evaporation when the air is not saturated.
Again I am speaking to the commercial smoker cooker. Which is usually at dew point when up to temp so the dry and wet bulb temperatures are no different.
If you want to talk about a commercial cured and mixed meat processor that controls dry temperatures, (for setting texture) humidity (for different cured products to be handled) and air flow (forced convection temperatures for controlled water loss in products) you can set up parameters where a wet bulb temperature is what the meat "may see" though it ignores the radiant energy the meat absorbs from the infrared spectrum.
But link your USDA source, be happy to read it and give you my thoughts.
Stall is also influenced by the power of the smoker/cooker.Thank you for the info.......I have learned something new"....I don't think everything stuck, but I did get a different view of how food cooks.........
I will stick with my no wrapping and cooking at 250-275....... Seems to have little or no stall, but if I get a longer stall then wanted or can afford I now have ways to address it....... Thank you....
I was asking because you sited USDA being wrong, just wanted to read what you read so I could comment. I figured when you stated that USDA was wrong you had read a specific USDA guideline.Okie, dokie!!!
A lot of the USDA's information doesn't contain scientific data for reference either!!!!!
See the other thread that I started, search USDA info for compliance guidelines for some pathogen lethality treatments and search some meat and food science books online or at the library.
You're asking for scientific data for reference, but you haven't provided a shred yourself.
I'm finished with this conversation.
Thanks!!!!
~Martin
bbally,
Can you please provide a few scientific references on water activity hysteresis equilibrium as a cause of the BBQ stall specifically?
My wife is a scientist and I'd like to have her take a look.