The days are getting longer, bugs are flying all over the place, and shorts are rapidly becoming the standard outfit for the day.  This means one thing:

It’s almost summertime.

And I don’t know about you, but I log in several hours around the grill over the summer.  So this week, let’s take a look at a delicious method of preparing…

BBQ

The first thing we should do is review our four main concepts of teaching science in the kitchen.

Now I know there are as many ways to prepare BBQ meats as there are people reading this blog!  However, we need to identify a couple of terms that are easily confused.  Grilling is the process of cooking meats directly on a metal grate directly over a heat source.  What I am going to look at today is barbecuing, which is a little different.  When you prepare BBQ you do not place the meat directly over the heat source.

Since it is not placed directly over the heat, BBQ meat is cooked much slower and at a lower temperature.  This helps to tenderize the meat slowly during the cooking process.  Yummm…..

Now that we have our terms straight, let’s dig into the science of BBQ!

SLOW DOWN WHEN PLAYING WITH ATOMS

You’ve heard me say that good food takes time to prepare.  Well, BBQ is no different!  When you are grilling, the meat is only a few inches away from a 2,500 °F heat source.  This will cook your steaks and hamburgers very quickly!  However, barbecued meat is slowly cooked within a (relatively) cool smoke around 200 °F.  Cooking tougher pieces of meat like ribs and brisket need this “cooler” temperature to slowly tenderize it to perfection!

You might think that the atoms in your BBQ meat get destroyed in such high temperatures, but this is far from true!

You learned in How to Teach Science During Breakfast – With Bacon that heat does a very good job at MOVING atoms all around.  As they move around, they slam into each other a lot and, at times, they bond with each other forming different groups of atoms.  This follows the Law of Conservation which states that atoms cannot be created or destroyed, only rearranged.

It may LOOK like those slow-cooked ribs were magically created while inside that BBQ grill, but the only thing that was changed was how the atoms were rearranged.

LET’S TALK ABOUT FLAVOR

The flavor that we love within our BBQ meats comes from many different sources.  Some of these flavors are naturally found within the meat itself while others are created when the atoms rearrange themselves throughout the cooking process.

However, there is one property of nearly all cooked BBQ meats that is the same – The Smoke Ring

The “smoke ring” is the thin area near the surface of the BBQ meat that has a very easy-to-see red or pink color.  You can easily see this layer when you pull apart or cut into your smoked meats.  You can see it very easily in the picture in today’s post.

THERE’S A LOT OF MOVEMENT GOING ON IN THERE

This thin layer of pinkish red color is caused by a gas (nitrogen dioxide)that is produced by the smoking wood in a BBQ grill.  This gas is not found within your raw meat.  So, when it is released from the smoldering wood into the grill, this gas diffuses into the meat and bounces into large molecules (groups of atoms) that we have learned about in a previous post – protein.

Most of the BBQ meat that you cook is loaded with large molecules of protein.  The particular kind of protein that gives red meat is red color is called myoglobin (“my-oh-glow-bin”.)  The cool thing about myoglobin is that the atoms that make up this protein bind together with the gases from the smoldering wood as the gas diffuses into the meat.  When this happens, the rearranged atoms give the meat a pinkish-red color.

This is why your steak or hamburger looks pink on the inside if it is not cooked entirely through.  Only SOME of that myoglobin has been affected by the gas.  As the meat cooks longer, more myoglobin proteins react with these gases to produce a grayish-tan color.

WHY DOES THE MEAT SHRINK WHILE IT COOKS?

The answer to this question should be pretty easy if you think about what happens to the water inside the meat when it gets heated up .  If you have ever cooked meat before, you have noticed that it shrinks as it cooks.  It saddens me every time I see it.  Watching those beautiful pieces of meat shrink away is torture.  However, this process is necessary to create such a tasty meal.  This shrinkage is actually a change in the density of the BBQ.

As the temperature of the meat increases, the water within its tissues begins to boil and evaporate into gas.  At the same time, the atoms within the fatty tissues of the meat begin to melt away as well.  All of these atoms diffusing out of the meat cause it to lose some of its density.

TO SUM UP ALL OF THIS DELICIOUS ACTIVITY…

Because of the law of conservation, the atoms within BBQ meat rearrange themselves into different molecules as gas diffuses through the meat’s surface.  At the same time, the density of the meat decreases as molecules of water and fat leave the BBQ.

Learn more about chemistry concepts in Classic Science: Chemistry for the Family and be certain to come back every Thursday or subscribe to The Blog of Mr.Q to learn more about how to teach science with cheap, everyday items!

Whether it comes from a box (ewww…) or is made from scratch (oh yeah!) you have to enjoy the cheesy goodness of the ever-popular…

Macaroni and Cheese!

I’ve put down more bowls of this gooey comfort food than I can count.  Despite the MASSIVE amounts of recipes out there (I received nearly 700,000 results from an Internet search for “Mac ‘n Cheese Recipes,) there is still ONE ingredient that remains the same in all of these dishes… the macaroni.

This week, we are going to take a look at what goes on inside our favorite curved pasta.  Before we do, be certain to check out the four main concepts you’ll need to explain the science behind Mac and Cheese:

Most of the macaroni you see either in a bag or stuck to a piece of artwork on your refrigerator door is nothing more than a hardened mixture of wheat flour and water.  In two previous posts, you learned that wheat flour is made up of many different molecules (aka – groups of ATOMS).

The majority of wheat flour (about 70%) is made up of an amazing group of molecules known as starch.  And after you add water to flour, large molecules known as gluten make up most of the remaining 30%.

Now when you place the uncooked macaroni into a pot of boiling water, all sorts of cool things start to happen!

We learned all about the science of water within the post on How to Teach Science During Breakfast…with Coffee.    Basically, the molecules within the boiling water receive a HUGE amount of energy from the stove.  This DIFFUSION of energy from the stove, onto the pot, and into the water causes all of the water molecules to start moving around a lot.

You’d move around a lot too if there was a fire under you?  I bet you would!

There is a lot more DIFFUSION going on when the macaroni finds its way into that boiling pot of water.  As soon as the pasta gets into the water, the starch within the macaroni starts to absorb some of that hot water.  Another way to say this is:

The water molecules begin to DIFFUSE into the starch.

What does that moving water do to the DENSITY of the pasta?

Nothing!

Density is defined as the amount of atoms found within an object (of a particular size.)  This means that every uncooked piece of macaroni has a measurable density.  But if you have ever spent time cooking pasta, you would know that pasta SWELLS as it is being cooked.  Since its size increases, its density will remain the same.

Don’t fall into the trap that so many people do!

You may BELIEVE that the swelling pasta is actually making new atoms to cause its increase in size.   BUT THIS IS NOT TRUE!   Remember the LAW OF CONSERVATION:

Atoms cannot be created or destroyed, only rearranged.

The swelling of the pasta is simply the diffusion of water molecules into the starch molecules!

Anyone can take out a box of instant macaroni and cheese, cook the pasta, and dump that weird-looking “cheese powder” into the mix.  But as we all know, good food takes time to prepare.  Below is my recipe for homemade Mac and Cheese.   I promise that once you try this recipe, you’ll never buy another box of “mystery powder” cheese in a box again.  Cheers!

Mr. Q’s  Macaroni and Cheese

Cook macaroni in plenty of water and drain.  Set is aside for a bit.

Melt ½ of the stick butter until foaming.  Stir in flour and cook (about a minute with CONSTANT stirring) until the mixture turns brown.  Wisk in the evaporated milk, nutmeg, dry mustard, and hot pepper sauce for 3-4 minutes until mixture is slightly thick and simmering.

Remove pot from heat and stir in the cheeses and ½ cup of hot water.  Stir until the cheeses melt, then stir in the macaroni.

Top with mixture of ¼ cup bread crumbs, ¼ cup Parmesan cheese, and ½ stick of melted butter.  Bake at 350 degrees for 20(ish) minutes in 9-in baking dish.

And, as always, good food takes time so….

SLOW DOWN and let this bubbly meal sit for 5-10 minutes before you eat!

Find out more about scientific concepts for your family within the Classic Science Curriculum

Be certain to check back every Thursday or subscribe to the Blog of Mr.Q for weekly updates.