There's a whole lot of “science” behind what makes good slow smoked barbecue recipes develop their flavor, tenderness, appearance, and moisture content. So, let’s take a few of the reactions and try to explain the science behind it...

Browning...

This is also called the Maillard Reaction. It is a reaction between amino acids in the meat’s surface and sugars in the presence of heat. The Maillard Reaction and the smoke introduced to the meat’s surface is what gives barbecue it’s characteristic “bark”. Usually, well smoked barbecue has a crust that is black in color suggesting the Maillard Reaction on overdrive. Don’t worry... this is a good thing. Most people love the “bark” on a properly cooked Boston butt or brisket.

Searing...

Most barbecue pit masters do not sear their meat before smoking. Searing meat is cooking it for very short amounts of time in an attempt to seal in the juices. Scientific tests have been performed which weigh two identical pieces of meat before and after cooking. One being seared and the other not. Test results show that the seared piece of meat lost more moisture than the not seared meat. If searing is done properly, it will improve the flavor due to the Maillard reaction, but it will probably not improve juiciness very much. This one is extremely controversial though. Many chefs swear by “searing in the juices”. Maybe there is something to it because after reading the paragraph on resting, you'll understand how the muscle fibers contract when heated and push the juices to the center of the meat.

The Smoke Ring...

The smoke ring is important for aesthetic reasons, but as far as flavor is concerned, it contributes none. The smoke ring is just a chemical reaction between nitrogen dioxide and the amino acids in the meat which produce a pink color. Nitrogen dioxide is produced when wood is burned at temperatures exceeding 600 deg F. Note this is in the firebox and not your cooking chamber. The smoke ring really has nothing to do with smoke at all. The smoke will impart it's flavor to the surface of the meat independent of the smoke ring reaction. Interestingly enough, gas grills do produce nitrogen dioxide. Some sawdust burning smokers that combust at lower temperatures do not produce nitrogen dioxide. Of course, ovens do not produce smoke rings, but what kind of jackass would cook barbecue in an oven anyway!? Note that in barbecue competitions, most judges do not know these facts and they think the smoke ring is caused by smoke and they do take that as a sign of properly smoked meats - especially brisket. So producing a good smoke ring is important.

Resting...

I can't say this loudly enough... make sure you properly rest your meat before slicing or pulling! As the outside muscle fibers in the meat heat up, they contract and push the moisture to the center of the meat. If you pull a piece of meat off the fire and set it on a cutting board, you'll see that some of the juices will naturally run out. If you cut the meat prematurely, about twice as much will run out. And you wonder why your brisket is so dry! Let the meat rest at room temperature. If it is too cold outside, wrap it in aluminum foil and let it rest that way. Do not put it in the refrigerator or ice box to rest. Let chicken and ribs rest for 15 minutes and butts and brisket for 30 minutes. Of course, always slice your brisket against the grain. And now would be a good time to tell you... stop poking holes in your meat! Every time you poke a hole in your meat, you can literally see the juices flow out! How stupid is that!? Poke it once with a meat thermometer and leave the probe in. Otherwise, use your hands or tongs to move your meat around. Injecting is a whole different story. Injections are done before cooking and they generally introduce a whole lot more moisture than they let out. Some of the moisture will leak out, but it's sort of an offset. The benefit being the introduction of more flavors to the center of the meat. Your meat probably will not be juicier, but it may improve the taste a bit.