Imagine this nightmare Labor Day scenario. You've invited a large group of friends over for pulled BBQ pork or a delicious beef brisket. That morning, you confidently place your meat in the smoker, handy digital thermometer in place so you'll know just when the internal temperature reaches the perfect point. Everything seems fine for the first two hours, but suddenly the temperature stops rising. And it stays constant for hours and hours, as your friends get hungrier and hungrier, and you're forced to order pizza in desperation.
You've just encountered the bane of aspiring pit masters everywhere: the Stall (also known as the Zone or the Plateau), a common phenomenon in low-temperature cooking. What, precisely, causes the stall is a perennial topic of debate among BBQ enthusiasts. Is it a protein called collagen in the meat, which combines with water to convert to gelatin at the 160°F point? Or is it due to the fat rendering, turning lipids to liquid?
Several years ago, Greg Blonder, a Boston College professor, did the experiments and came up with a definitive answer: evaporative cooling. The meat sweats as it cooks, releasing the moisture within, and that moisture evaporates and cools the meat, effectively canceling out the heat from the BBQ. These days, Blonder is the resident science advisor and myth buster at the popular BBQ and grilling site called Amazing Ribs. "I spend a lot of my time settling bar fights, basically," he joked.
A slow-cooked passion for 'cue
Blonder has been an avid, inventive cook ever since college, when the only tools he had to work with were a single hot plate and pot. When a friend once visited from Hawaii, they roasted a whole pig on hot rocks in the backyard. Ever the scientist, Blonder stuck a pair of thermocouples into the carcass to monitor the changing temperature as it cooked. So naturally, when he heard about the stall, he decided to test it experimentally.
First, he charted the actual stall. He used brisket and pork butt for his experiments, since they are the most popular meats for slow-roasting and smoking. He used a thermostatically controlled smoker for the cooking and maintained a careful 150°F. As expected, the stall set in after the first two to three hours, and it lasted roughly six hours before the internal temperature began rising again. It's a handy example of a simple phase transition, with an initial rise and then a long leveling off, before rising yet again to move towards the critical tipping point.
Blonder found that collagen is unlikely to be the culprit because it only accounts for about one-fourth the total protein in, say, a pork shoulder (18 percent, with 65 percent water and 15 percent fat). The basic hypothesis is that the collagen sucks up so much energy as it chemically converts to gelatin, there's not enough left for the meat to continue increasing in temperature, and you get the stall. True, the collagen starts to melt at about the same point as the stall kicks in, but according to Blonder's calculations, that's just coincidence. There just isn't enough collagen in the meat. He proved it by wrapping one six-pound pork butt in tinfoil prior to cooking and using just a rub on the another six-pound butt. There was no stall in the foil-wrapped pork butt, and there should have been if collagen was the cause.
As for the melting fat hypothesis, Blonder tested that, too. He placed a lump of pure beef fat into a smoker along with a sponge soaked in water, stuck thermocouples into both, and cooked them at 225°F. Once again, there was no stall with the beef fat. But the sponge showed a marked stall after the first hour, and the temperature didn't start to rise again until all the moisture had evaporated. Voila! The culprit is evaporative cooling.
That's why today a growing number of competitive pit masters wrap their meat in tinfoil after the first few hours (usually when the internal temperature hits 170°F), along with a splash of apple juice, beer, or even Mountain Dew. Blonder doesn't, because the tradeoff is that you don't get the crusty, flavorful "bark" on the surface of the meat—a product of the evaporative cooling removing so much moisture from the surface—and he likes the added crunch and "flavor bomb" when he shreds it in with the rest of the meat before serving. But he recommends the tinfoil if you're not an experienced pit master, especially if you're using a big offset grill with a lot of airflow (compared to an egg or Kamado). The tinfoil trick can reduce the cooking time by half if you're cooking at the standard 225°F. "It's absolutely foolproof," he said. Raising the cooking temperature to 250°F can shave another hour or two off that. Or, you can just do it the old-fashioned way and tough it out for the full 14 hours.
If 14-15 hours just seems like too much of a day-long commitment for your Labor Day festivities, Blonder suggests trying something he calls pork-us interruptus: start the process the day before and when the pork butt or brisket hits the stall, take it off the smoker, wrap it in foil, put the foil-wrapped meat in a plastic bag, and dip it in ice water to cool. Next, store the meat in the refrigerator overnight and finish cooking the next day. He insists you can even finish it in your oven, because you already have the smoky flavor in the meat. "It takes the stress off the chef," said Blonder. "Because the worst thing you can do is panic when you hit the stall, and your guests are showing up and you don't have any meat."
One more handy (scientific) tip: you should pre-salt your meat for several days beforehand, because it takes that long for the salt to diffuse into the meat. Salt is essential to the cooking process, because it adds flavor and reduces moisture loss, preventing over-shrinkage. But be aware that some cuts of meat are pre-injected with phosphates, and if you add salt on top of that, it will be too much. That's also why Blonder doesn't add salt to the mix of spices he uses in his go-to rubs. (He says you can add the rub or a marinade a few hours before cooking; it's not going to penetrate that deeply regardless.)
Blonder is adamant that these are just useful tips, colored by his personal preferences, and that there is plenty of room for adaptation if your tastes happen to differ. "I'm never going to tell you there's only one way to do it," he said. "But if you want to achieve a certain goal, there are better ways to achieve that goal through science."
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Ars Technica
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