Science of BBQ from Smoke, Wood, to Meat & Fat

how bbq works featured

Why does meat, after basking in a warm smoky cloud, yield exceptional BBQ? Of course not just any smoke — we can’t just fire up a bunch of cardboard and newspaper and end up with good brisket — it takes a quality cloud built from specific woods. And what about the food before, during, and after the process? If we can understand some these parameters we will better know what needs to happen to get better results. 

Mastering the art of great BBQ and smoked meats starts with understanding the chemistry of meat, fat, and last but not least, smoke and fire. In this article we explore the science, the why, behind successfully smoking meat. We’ll also do a little myth busting around commonly believed theories on BBQ and grilling. All this BBQ geekdom to help you understand basic factors that dictate the quality of your BBQ.

Apply dry heat get moist food

That phrase doesn’t make sense unless we know the chemistry of meat. There are three components that give a moist juicy and enjoyable end result:

  1. Water
  2. Fat
  3. Collagen

Each of these three elements are affected by heat in different ways, and also by the chemical compounds around them, and equally as often, by each other.

Yes, we know the best smoking environment uses humidity in the process, sometimes naturally, sometimes an addition we control, and sometimes because the meats add vapor to the environment. Smoking is however, considered a dry cooking process, especially when compared to braising, stewing, or steaming.

Meat is Mostly Water

Lean muscle tissue composition

Lean muscle tissue composition

Many of us have been told that we are 98% water, or some equally high number. That is slightly exaggerated, but we, and the meat we cook, are certainly composed of a very high percentage of water. Beef, veal, lamb, and chicken average about 73% water content, pork and meatier fish fall just under 70%, delicate fish can exceed 80% water content.

Another big component of most meats is myoglobin, cousin to the better publicized hemoglobin in our blood stream, with a parallel function in the body and similar iron content for a red color. Myoglobin is a water soluble protein that is an attractor and binder of oxygen for the cells.  Myoglobin is also responsible for the coloration in the meat itself, the deeper the red color the higher the concentration of myoglobin.

When meat is cut, the juice we see on the plate is a mix of water from the ruptured cells and the myoglobin, which is what gives juice the reddish hue.

When subjected to heat, myoglobin loses its red coloration, fading to pink and eventually gray or tan in color. This is one of the more noticeable visual cues of cooking meat. In steaks and chops, or meats that are kept to lower temperatures and doneness (medium rare for instance at 135 degrees +/-), the flesh is still bright red and juices free flowing. Well done meats have the juice and the color cooked out of them, which in a steak or quickly cooked cut makes for a dry end result. So juice, mostly water, is the first aspect of a moist end product.

Increasing the temp and keeping it moist

COOKING WITHOUT OVERCOOKING
man reading temperature of food on phone

Fat is the next component of meat that we associate with moistness in the end product. Fat is also a huge component in the textures and flavors of meats. Animal fats store flavor compounds from what the animal consumes and produce over their life (this gets interesting with grass fed beef).

comparing intermuscular fat

We see more desirable intermuscular fat in the grain fed cut.

These flavors they store in the marbling/intermuscular fat are omnipresent in differing amounts; just under the skin are subcutaneous deposits, between muscles is intermuscular, and intramuscular is within the muscle fibers giving us our favorite, marbling. With concentrated caloric values, fats, along with oxygen, are the main fuel that power muscles in animals.

wagyu cut

Desirable cut from Pacific Rogue Wagyu Cattle Company

Fat contents vary greatly between types of animal meat, and the different cuts within the category. Being aware of the fat content is crucial to maintaining moistness by the end.

comparing types of meat chemistry

The table shows that the lean of the three major carcass meats is similar in gross composition, which should not be unexpected because they are in effect mammalian muscle; the poultry muscles have less intramuscular fat and most of the fat is associated with the skin, although it is not subcutaneous as seen in mammals.

Animal fats begin melting in the 130-140 degree range. As the temperature increases the expansion of the other tissues will begin to squeeze out the fats.

Taken too far and cooking the meat too fast, will force out the fats resulting in a dry end product.

We know that the magic number for doneness of brisket and pork butt is over 200 degrees, so we need to understand the relationship with fat and temperature to help us get that ideally cooked texture and moistness to enjoy, this is where the next component becomes an equally important factor.

Low and slow with the heat

muscle meat composition illustration

Muscle meat composition

Intertwined with the muscle meat and fatty deposits are the connective tissues. We’ve all seen the tendons that stand out in meats and the silverskin they often flatten into. These are much of what we think of as gristle, and they are known for tightening up when heat is applied and becoming tough nuggets of stuff that is impossible to chew.

Similar to marbling, there are softer connective tissues throughout the meat called collagen. They also appear as almost invisible tissue surrounding the fibers and sheaths that hold muscle groups together, along with invisibly entwined throughout. Slapping them with high and fast heat will cause them to become rubbery and chewy. However, if they are slowly heated they are the source of a rich smooth well textured material called gelatin.
smoked brisket
Gelatin sounds like the name of a jiggly fruit dessert because originally that was made from the rendered animal collagens. This richly textured liquid is what makes your slowest smoked meats have great textures. When warm it has fluidity while retaining a silkiness of texture, as meat cools it permeates back into the areas around the cells and structure ending up as noticeable ‘moisture’ in your end product.

Louis-Camille Maillard

Now we have a broader understanding of what happens inside our meats during the smoking process. But how does the outside end up so differently tasty and textured? Again, there are a few answers, but we will focus on two aspects. First the Maillard reaction creating our bark. Second the ‘Ring’, as the pink halo around the edges of well smoked meat is commonly known.

MAILLARD REACTION AND CARAMELIZATION

Both a physician and chemist, Maillard codified the reasons why food gets brown; crusts on bread, crispness on fried foods, the exterior colors of seared meats, etc. It would be easy to dismiss it all as simply caramelization, or the browning of the sugars naturally present and added by the cook. And some of it is based on that, the application of heat causing steadily darkening coloration as more heat or more time are added.

completed pork butts

But Maillard realized there is another chemical reaction in play to get the exteriors we love so much. In 1912 he posited that enzymes present in food, and the amino acids they are made from, interact with the caramelization to get the full reaction of an enjoyable browned exterior to the food. You can go down the rabbit hole of how pH is involved, or the secondary Maillard reactions with ketosamines and a slurry of other compounds. For our purposes, we are going to suffice it to say when heat is applied the exterior of our food takes on deep rich colors from amino acids combining and enhancing caramelization.

There is a very important factor that directly applies to those of us geeking out with our smoker. The Maillard reaction is not just about temperature. It is really effective when temperatures hit around 300 degrees, the reaction takes off. However, you can achieve similar results at lower temperatures for extended periods of time. Twelve hours at 225 degrees will get you similar results to about a 350 degree exposure for an hour. The longer time helps the breaking down of fats and collagens and the tenderization that results. And it allows for the development of the iconic smoke ring.

Put a ring on it

pinkish ring around the edges of smoked brisket

As much as our brain wants to say the smoke causes that delightful pinkish ring around the edges of say a brisket that is not exactly what has happened. It goes back to our friends the myoglobin present in meats. Fire releases carbon monoxide (CO) and nitrous oxide (NO). These two compounds interact with the iron in the myoglobin, essentially freezing it in place to cause a permanent pink-ness to stay in the cells of the meat. These gases, not the smoke itself, create the ring, and can occur even in a cooking environment that has zero smoke.

Every time you look at the ring around the edge of your smoked meat, you get a visual representation of how far the CO & NO were able to penetrate before the heat beat them to the myoglobins making them turn gray, with the temperature winning out at about 170 degrees. The penetration of these gases maxes out just shy of one half inch, and is more typically abut an eighth of an inch into the meat.

Because this is a race, you can influence the results. Using brisket again, we all know of the stall; moisture on the exterior of the meat evaporates keeping it cool so the cooking process stalls. What we just said there, “keeping it cool”, that is the trick. Our old friend spritzing or mopping will aid with a deeper pink ring, along with a water tray in the smoking chamber. The water on the meat’s surface actually latches on to the smoke, containing the CO and NO molecules, allowing better penetration.

The chemistry of smoke

lighting wood
Now that we have a bit of the science regarding the ring of color that comes with smoking food, and the idea that the smoke itself does not cause the ring, let’s look at what smoke actually does to flavor our food. Of course, we need to look backward a bit at the science of the wood’s composition. What we will not do here is talk about different wood choices, that alone is books of information, and loads of it available for your research.

A couple basic tenets for this area. Wood needs to be dried, preferably air dried. Green wood burns too inconsistent, produces too much steam, and can carry nasty flavors to the food. Even dried wood contains some water, but it goes down from about 50% to well below 10%. After drying Cellulose is the most common component, Hemicellulose next and then Lignin. In general, the harder the wood the higher the Cellulose and Lignin content. There are also a handful of trace elements and minerals in wood.

So, we light it up. We know that CO and NO are present when we get the temperature over about 700 degrees. There is a whole slurry of other gases present. We want to keep the temp high at the combustion site. Lower burning temps are what create the oily white some that is actually a negative flavor component of your food. That’s right, white smoke bad, blue smoke good. Barely visible blue smoke is cleaner with less impurities so it imparts more pleasant flavors. It also contains guaiacol, a near cousin to creosote. Creosote can be nasty, guaiacol is the positive flavor component that we love and associate with good smoked foods.

Nearly invisible clean blue smoke carrying the smallest particles (as opposed to white smoke with larger visible particulate) enveloping our food with guaiacol and other milder flavoring agents from the gas slurry is the goal that we have for well smoked meats. Even with all the right components, the smoke and flavor will adhere better to a pebbled surface, facilitated by a rub, and a moist surface either because of the moist smoking environment or by basting the food as it smokes.

Its brisket time…or whatever

COOKED BRISKET ON FOOD TRAY

Let’s walk through all of this quickly as we look at a piece of brisket being smoked.

We start burning fuel creating a nice cloud of NO, CO, and smoke, along with an environment heated to 225°F.

We put our rubbed brisket in the smoking chamber along with a pan of water. Slowly the internal temp of the meat begins to rise. All the while the NO and CO are binding with the myoglobin to create a nice pink ring into the meat. Warming up further starts the fats liquefying and permeating down through the meat. Also during this process we have initiated a slow version of the Maillard reaction, enhanced by caramelizing any sugars we have in the seasoning rub we applied.

As we crest 150°F or so inside, the collagens begin to melt, the fibers of the meat start releasing and tenderization gets going. Soon the myoglobin will fade into the pale gray color of fully cooked brisket, the bark thickens as the Maillard reaction keeps delivering the goods.

By the time our interior temp is 203°F we have nice bark, a good ring, and a center of meat fibers softened and permeated with flavorful fats and collagen, and residual water left in the cells because we didn’t heat them so quickly they burst. For more detail, see our Smoking 101 guide.

BBQ Myth Busting — Smoking Out the Truth

MAN HOLDING MYTHS CARDBOARD
We all miss those guys busting myths that we all know are fact…until they get through with it. Deep down we all just wanted their gig, what a job! We’ll take that role over for a bit here albeit without explosions and such. There’s a lot of great information about smoking grilling and preparing meats, and most of it is accurate. Emphasis on most, and unfortunately some of the inaccuracies are in the field of doneness, making sure that your food is cooked to a wholesome safe degree. We’re going to dispel some of those ideas along with a variety of myths that we all know are facts…for now.

Longer marinating times imparts more flavor
There’s a couple flaws here. Meat is already a high percentage of water, so it has low absorption of more fluids. Oil base marinades do not penetrate the cells, and even fluid will only flavor the outer layers. To get flavors deep in the meat, use an injector or larder to get to the center. Salt, is the exception as it has amazing penetrating capabilities which is why dry rubs are very effective.
Smoking is a dry cooking process
Technically it is referred to as a dry process in that the food is not in direct contact and with a liquid for the heat transfer while cooking. Do not take that to mean your process should be dry and arid. Use a water ray in your smoking chamber. Baste frequently. Moisture is your friend for flavor and heat transfer.
Soak those wood chips
Yeah…no. Hardwood is intentionally dried to get the water content into the single digits. Because wet and green wood put out nasty smoke. There is no benefit to undoing that process. If flame up is your concern, wrap the chips in foil, use a metal box or stainless pouch. We want moisture in the smoking chamber, just not a bunch from the wood.
No peeking, you’ll lose too much temperature
Again, technically accurate, yes some heat escapes. But the old adage “If you’re looking you’re not cooking” and a peek adds 15 minutes of cook time is inaccurate. Your whole goal cooking is to transfer heat to the meat, and guess what? Meat holds temperature really well. So the air may will cool a bit, but you meat is fine for a few minutes. Baste, rotate, temp check, whatever; work without fear for a minute or two.
That meat is bloody
Blood is thick viscous fluid that congeals and dries firm. Juices in meats are not blood or your plate would look like the inside of an abattoir. Cells contain myoglobin which is iron based like hemoglobin, but present in much lower concentrations. When the meat is cut water from the cells mixes with the water released from the cells and you end up with juice. The redder the meat and juice the more myoglobin present.
Clear chicken juice means it is cooked
Chicken also contains myoglobins that color the juice, but not many, and their red may cook away before the meat is fully cooked even though the juice is clear. Conversely, some chicken juice will never run clear. The only accurate way to tell if your chicken is fully cooked is with a thermometer. The recommended safe internal temperature is 165 degrees to insure the safety or your guests and family.
Poking with a thermometer creates juice loss and makes it dry
Of course a little juice will leak out when the meat is poked. Keep in mind that every cell in the meat is about 70% water. Yes, you rupture the few that are in the path of your thermometer. That’s it. The vast majority are intact and waiting for you to enjoy their juicy splendor.
Well done means dead and dry
Yes, you can massacre a steak or chop to dryness. In counterpoint, one word; brisket. That’s right, you cook that to just over 200 degrees inside and it still has great moisture from all the collagens that you have broken down through a low and slow cooking process.
Just knowing the time cooked is enough to determine doneness
There are way too many variables in this equation for it to work. They include the starting temperature, the actual density of the meat being cooked, the consistency of the heat source, etc. The best way to determine doneness is always checking the internal temperature with a thermometer. The obvious exception is an item that only needs a sear to finish.
Letting meat rest doesn’t help
This is a controversial topic. Most experts agree that the time it takes to get a steak to the table is adequate rest before cutting. More importantly, scientific testing has shown that meats cooked low and slow retain as much as 90% more fluids if they are allowed to rest before cutting. This is your brisket, pork butts, ribs, etc. You use patience in your process, don’t stop right at the end.
  • Jill says:

    i was so ready to buy a smoker…I cant come to terms with eating something that was coked with propane….but now i read lots saying that smoking is equay as harmful as propane and charcoal grilling….I thought smokig wd be healthier.. a penny for yr thoughts?

    • Kat says:

      Hi Jill, very good question/observation first thing to consider is that you can get a propane smoker which is easier to operate, a charcoal smoker which can be more difficult or an electric smoker which is a cleaner/healthier. The second thing to consider is the smoke you generate. There’s plenty of articles out there but to summarize; darker smoke is the one that contains the harmful components and a lighter blue/transparent smoke is deemed “safe(r)”. A third thing to take into account is that smoking is an indirect method which does not expose your food directly to the fuel. On the negative side though, you are dealing with food exposed for a prolonged period of time to smoke which is the residue (or waste) of combustion. So my advice overall is go with an electric smoker that can accommodate a box, use chips from a reputed company, control your smoke to ensure your smoker is properly ventilated and most importantly don’t overdo it on the smoker. I consider a smoker like I consider pastries: a treat. Once is a while isn’t bad but I wouldn’t do it everyday. Last but not least: if you’re not comfortable with it, don’t feel compelled to jump on the bandwagon just because of the trend. Hope this helps.

  • William says:

    Just to be a total geek I need to clarify. Smoke isn’t actually created by the process of combustion. It’s actually the process of incomplete combustion. The wood it’s self isn’t technically burning. The wood is turned to gasses (Smoke) and the gasses burn or as we would like it don’t burn.
    Bill

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