By K. Nepsa

Last month, we discussed the science behind the visceral response we often have to BBQ. Whether you’re a beginner to the BBQ or a seasoned pitmaster, you may have experienced what’s called the “plateau” or the “stall.” The temp rises steadily for a couple of hours and then, to your chagrin, it stops. It sticks. It stalls for four or more hours and barely rises a notch. Sometimes it even drops a few degrees. In the meantime, your guests begin to arrive and your partner starts to look a little stressed. Why does this happen?

Many have long believed that the stall was caused by a protein in the meat called collagen combining with water and converting to flavorful and slippery textured gelatin. Called a “phase change” the conversion of collagen starts happening at about 160°F. Others have speculated that the stall was the fat rendering, the process of lipids turning liquid. Still others thought it was caused by protein denaturing, the process of the long chain molecules breaking apart.

It turns out, the answer is much simpler. The stall is caused by the simple process of ‘evaporative cooling.’ The meat is sweating, and the moisture evaporates and cools the meat just like sweat cools you after exercising.
The person who figure this out where so many others have failed, is Dr. Greg Blonder, a physicist, entrepreneur, and former Chief Technical Advisor at AT&T’s legendary Bell Labs. He is also an avid cook and set out to find answers to this frustrating dilemma. In summary, the fuel in your cooker (oxygen plus charcoal, gas, or pellets) burns and produces energy which enters the cooking chamber in the form of heat. Some of it escapes through the metal sides and some goes out the vents, but some is absorbed by the cold meat. When it heats, some of the energy is used up raising the temp of the entire hunk, some of it is used in changing the chemistry and physical structure of the molecules in the meat, and some is used to melt fat and evaporate moisture.

Some meat with relatively high connective tissue content are made of really tough stuff called elastin. But some are made of collagen. However, there’s just not enough collagen to suck up all the energy necessary to prevent the meat from increasing in temp.

Hypothesizing that the stall might be evaporative cooling, Blonder took a lump of pure beef fat from the fridge, inserted a thermometer probe, and placed it in a thermostatically controlled smoker. He also soaked a large cellulose sponge in water, shook it out, inserted a probe and placed it next to the fat. Then he set the smoker for 225°F. The results were pretty clear. The fat did not have a stall at all. It slowly and steadily heated on a nice gradual curve. But, the sponge stalled. It climbed at about the same rate as the fat for the first hour to about 140°F, and then it put on the breaks. In fact, it even went down in temp! When it dried out after more than 4 hours, it took off again. Blonder points out that the size, shape, and surface texture of the meat can influence the stall by influencing how much moisture is available for evaporation, not to mention airflow and humidity in the cooker. He also notes that meat won’t stall at high temps.
So, how do we fix the stall? Traditionally, pitmasters have used foil at approx. 170°F with a splash of liquid in a process called the Texas Crutch. Based on Blonder’s data, it’s recommended that you wrap the meat at about 150°F, after about 2 hours in the smoke. By then it has absorbed as much smoke as is needed. If you wrap it then, the meat powers right through the stall on a steady curve and takes much less time. It also retains more juice. However, if you’re old school, no problem…just be sure to season your meat with a good amount of patience as well as spices!

K. Nepsa has a B.S. in Geology and a Master’s in GIS. She has lived in Arizona, HI, CA and Shanghai, China. Her hobbies include enjoying the outdoors via Jeep, Kayak, horse or foot. She has been a Vail resident since 2005.

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