[ intro ] It’s summertime for those of us in the northern
hemisphere, which means one thing: barbecue season. This style of food prep is a summer favorite
because it’s all about heat, flames, and how to control them for the tastiest meat
or veggies. And just like your kitchen at home, there’s
plenty of overlap between a chemistry lab and your backyard barbecue. So here are five science-based hacks that
you can use at home to step up your barbecue game. First things first: whether it comes from
a cow, pig, fish, or edible vertebrate of choice, that protein-rich slab of meat is
muscle. And land-based animals have layers of connective
tissue wrapping those tiny muscle fibers into bundles. A type of connective tissue called perimysium
wraps those bundles into larger bundles. This bundle-ception continues until it’s
no longer microscopic. You can even see the bundles if you look closely. But the way that the connective tissue wraps
around muscle fibers determines the grain of the meat, or which direction those bundles point towards. Now, some cuts of meat like skirt steak or
flank have a thicker, more easily visible grain. They have larger muscle bundles with lots
of connective tissue compared to something like tenderloin. This makes them tougher to the bite, which
is where this tip comes in handy. Cutting at a 90 degree angle to the grain, as opposed to parallel with the grain, will
result in a more tender bite in your mouth. How do we know? Well, tenderness is a hugely sought after
quality, so folks in the meat industry actually measure this. But you can’t just have a group of people
taste testing burgers all day, so a procedure called the Warner-Bratzler
Shear Force test was invented to objectively assess meat tenderness. You basically take a tube-shaped section of
meat and put it under a mini guillotine, then measure how much force it takes to cut
through the sample. This test mimics what we do with our teeth
when we bite into a steak, so it’s a pretty good standard for objectively
measuring tenderness. Now, back in your backyard, by cutting perpendicular
to the grain, you’re separating the muscle into a cross
section: short muscle fibers separated by that structurally
weak connective tissue. A 1985 study in Meat Science -- which is a real, peer-reviewed journal
-- showed that perimysium broke down much more
readily than muscle fibers. So by cutting across the grain, you’re letting the heavy butcher knife do
the work of breaking down the muscle so your teeth don’t have to. Most of the time, adding heat is a predictable
experiment. The longer you cook something for, the hotter
it becomes until it burns to a crisp. But something different happens when you slow
cook meat on a barbecue. It’s a phenomenon known as the barbecue
stall. The internal temperature of the meat will
climb for a while, but then level out -- even though it’s still over hot coals. The internal temperature might stall for hours, leaving you to wonder if the gods of thermodynamics
have somehow cursed your grill in particular. A few explanations have been offered. Like, maybe the heat energy is selectively
melting the fat. Another is that collagen, a protein in connective
tissue, turns into liquid gelatin when temperatures get above 70 degrees Celsius. But stalling happens at an internal temperature
around 60 to 70 degrees Celsius, too cool for collagen to gelatinize or for fat to melt. So a more likely hypothesis is that this leveling
out is due to evaporative cooling. Water inside the meat evaporates and carries
heat away -- much like how sweat cools our skin on a hot
day. Then once the meat dries out a bit, the internal
temperature finally starts to rise again. Now, researchers from Texas A&M University
attempted to measure this a few years ago at a food-themed outreach event. They did their experiment in the most Texan
way possible: they threw a cookout and measured the stall
in real time. To do this, they compared the internal temperatures
of brisket wrapped in foil to totally exposed meat, and they found that meat without foil experienced
a stall at sixty degrees for about two hours, but the foil-wrapped meat didn’t. They concluded that the foil prevented the
evaporative cooling effect, so the meat continued to rise in temperature. In two thousand eleven, a physicist performed an informal citizen
science experiment where he took a chunk of beef fat and threw it in a smoker alongside
a sponge filled with cellulose water. Fat is hydrophobic, meaning it doesn’t store
water like muscle does. So it shouldn’t experience any stall from
water evaporating. Sure enough, the sponge experienced a temperature
stall comparable to a proper brisket. On the other hand, the fat heated up steadily
and ended up as a glistening puddle on the bottom of the smoker. When you think of marinades, you probably
think of the good old immersion technique. Soaking the meat in some kind of salty, flavorful, or acidic liquid for a long period of time
can do everything from adding flavor to tenderizing before meat hits the grill. But it’s more complicated than that. Certain ingredients are better at certain
jobs than others. Marinades like brine or soy sauce can be used
as a tenderizer because of their high salt content. That’s because salts are good at breaking
down what are called myofibrillar proteins, namely actin and myosin. In a living animal, these filaments slide
past each other to perform muscle contraction, but when muscle becomes meat, they’re still
complex, interlocking structures. Luckily, the salts can unfold them. Specifically, the negative chloride ion in
salt binds to the filaments and creates an electrostatic repulsion. While the filaments are usually tightly packaged,
this repulsion spreads them apart and lets water molecules trickle into the newly opened
areas. It’s like using similar poles of a magnet
to repel each other, but instead of magnets, you have similarly charged ions. This increases the space between strands of
protein, which lets the muscle hold on to even more
water. Now, sometimes you might choose acidic marinades
like lime juice, lemon juice, or vinegar, which tenderize meat slightly differently. Marinades with a low pH do help break down
some of that connective tissue and add flavor to the meat, but don’t increase the meat’s ability
to hold onto water. One solution, according to a 2007 review in
the journal Applied Poultry Research, was to combine the water-retaining properties
from salty marinades with more acidic solutions to get the best of both worlds. A final type of marinade involves using enzymes
from fruits, like papain from papayas or bromelain from
pineapples. These types of marinades tenderize meat by
breaking down the connective tissue between muscle bundles. As for how long you should marinate for, that’s
up to you. Researchers in 1999 found that chicken fillets
experience their biggest uptake in water during the first five minutes of marination, with much slower absorption in the half hour
afterwards. But a study published in 2010 compared the
effect of marinating time on servings of chicken and found that the best tasting fillets resulted
from a three hour soak time, compared to 30, 60, or a 120 minutes. So do you really need to marinate overnight? Well, you can see some benefit in just a few
minutes, but you might notice more flavor after a longer soak. Look, we’ve all been there. Figuring out the delicate balancing act of
exactly how many seconds in the microwave makes the difference between a burrito that’s
frozen in the middle versus one that tastes like rubber. And grill masters run into the same problem,
just with really big slabs of meat. They want to end up with a brisket that’s
both tender and juicy, which is tricky. Meat needs to reach a certain temperature
threshold for some of its tougher elements, like collagen, to break down. But crank up the heat too high and you’ll
lose more water, making it taste dry. Enter slow cooking — using low temperatures applied over multiple
hours of cooking time to get exactly the right internal temperature. And that precision is necessary because different
chemical events happen at different temperatures. By fifty degrees, you've already started denaturing
some of the proteins in meat, like myosin. The tough connective collagen starts to denature
and become gelatin between sixty and seventy degrees. But, you want to stick to the lower end of
that range, because the enzyme that helps break down collagen is only active under sixty
degrees. And that process takes its sweet time. A 2005 review found that it took more than
six hours to see significant tenderization benefits from slow cooking. So the sweet spot seems to be an internal
temperature around sixty, definitely not higher than seventy degrees — that way, the proteins that are tough to the
bite have denatured, which tenderizes the meat. Meanwhile, it’s lost as little moisture
as possible. Even just a few degrees hotter and you risk
losing the benefits. Although increased temperatures will further
denature collagen and turn it to gelatin, the meat overall starts to shrink as water
is lost. That means the other proteins in the meat
will start clumping together, making it tougher. Researchers in 1968 reported that as meat
rose above sixty degrees Celsius, the tenderness progressively decreased. Basically, the extra breakdown of collagen
can’t compensate for the toughness caused by the other proteins condensing. This is why slow cooking is desirable. There’s little room for error when you’re
aiming for the best balance between juiciness and tenderness. You need to hit a super precise temperature
target, and slow cooking makes that easier to do. Other than keeping you from burning your mouth,
allowing barbecued meat to rest for a few minutes after taking it off the grill will
actually help it retain moisture. Usually that means taking meat off the grill
and subjecting it to less intense heat before slicing into it. During cooking, some of the proteins, including
actin, myosin, and collagen, shrink together, which decreases the amount of space available
for water to hang out. Think of any time you may have overcooked
a chicken breast. It probably shriveled up and dried out. Now, at certain temperatures, the proteins
shrink irreversibly. Contrary to the popular belief behind this
practice, these proteins don’t get their structure back if they cool down. Once they’re heated up, they stay in that
misfolded shape. But other mechanisms can reabsorb some of
the water that’s been squeezed out. It’s been hypothesized that capillary action,
the phenomenon where water moves through thin columns on its own, could play a role. On paper, the spaces between muscle filaments
could pull up a column of water up to three hundred meters -- if you could find a slab of meat that big. But it hasn’t been investigated specifically
in reference to the resting effect. But a lot of water stays outside of the filaments,
so regardless of how long you rest the meat, you still can’t hold on to all of it. Unfortunately there’s no universal law for
how long you should rest the meat, but as a general rule, the larger the roast,
the longer you wait. So next time your friends laugh at you for
claiming science can enhance your barbecue, show them the light with your flawless brisket. All it takes is a little understanding of
the chemistry of protein, fat, water, and salt. Thanks for watching this episode of SciShow. If you liked this one, you might like our
podcast SciShow Tangents. Each week we get together to astound each
other with science facts -- with an ever so slight competitive twist. We even have an episode on the science of
cooking. So check out SciShow Tangents wherever you
get your podcasts. [ outro ]
