The physics of bacon

[mamster]

I've always noticed this phenomenon when cooking bacon, but I always think of it at the wrong time to post. Now, the time has come.

The fat streaks in bacon go through three distinct phases. Out of the fridge, they're white. After a few moments in the hot pan, they're translucent. By the time cooking is done, they're somewhere in between. The most interesting part of the process is the transition from translucent to crisp. The fat doesn't cook steadily. Suddenly there will be a hiss, and a section of it will turn nearly opaque. This was amazing to watch on some thin-sliced guanciale I was cooking the other day. Pop! You could watch the color change shoot along the strip of cured jowl. Stirring the bacon seems to accelerate the process.

What in the world is going on here? It looks almost like a crystallization reaction. This is a very important question for physics, and I'd like to see our Einsteins on this thread soon. Thank you.

[FoodZealot]

I'm no physicist.

I'm no scientist.

But I loves the Pork. That's right, with the "s".

I'm honored to be first on this profound topic. My guess is some sort of critical mass is reached with moisture, kinda like popcorn bursting or when you're steaming sausages and the liquid boils away and they start to fry.

~Tad

[Stone]

Stop thinking so much. Eat.

[Human Bean]

Dunno the answer to your question, but maybe it's a protein-denaturing thing like egg whites. Although the predominant part of the white stuff is fat, maybe there's enough protein to do the egg white thing.

When I cook bacon (Mmmm, bacon) it's in the microwave, so I never see that.

You're a biologist, maybe you can tell us...

Edit: 'cuz I've never heard of guanciale before. Ewww.

Edited August 15, 2003 by Human Bean (log)

[Really Nice!]

Any scientist out there feel free to correct me... but here's some text from my culinary school notes that I'm applying to the question.

Animal fats turn solid in cold temperatures and as a part of that process they cloud up. I believe this is because animal fats have a longer 'fat chain' and are more closely to being fully saturated. This means they can pack together more closely, and in doing so, they 'cloud' up.

Vegetable fats do not turn solid in cold temperatures because they are either mono unsaturated, or poly unsaturated; they have a shorter fat chain. Either way, they're lacking some hydrogen atoms contained in the fat chain. This keeps them from solidifying. This keeps them clear.

After a few moments in hot pan, the bacon turns translucent. Actually, this is true of any animal fat. I believe this is due to the fatty chain breaking down because of the heat. Exactly what happens with the chain, I do not know. It could be either the hydrogens or carbons evaporating in the chain and causing the breakdown.

It turns somewhere in between because the heat is high enough to caramelize the fat. Another way to look at this is to cook bacon in an oven at about 250F. You'll never be able to get to that "somewhere in between" point because it isn't hot enough to perform the 'maillard reaction'.

Again, any food/rocket scientists out there that can verify/destroy this theory, by all means please do.

Oh, and Mamster, did you remember to ask because of my post?

[Human Bean]

Although McGee is a room or two away at the moment (the book, not the man), it's too late and I'm too tired to look it up. Nonetheless, I don't think that fat itself can carmelize (Maillard reaction), that'd be carbs (sugar) and/or some amino acids from protein.

Most bacon certainly has sugar which can brown (dunno about that pig jaw, er, stuff) but that probably wouldn't be the same thing as turning opaque, (or quasi-crystallizing, as our bio-scientist puts it, more-or-less).

[jackal10]

I think (but have done no measurement) that there are three phases, as the temperature increases:

a) The fat melts. This is the change from white to translucent That is quite low 30C-50C. If you have some bacon grease and a digital thermometer you can measure this.

b) The trapped water boils, This is the change to cloudy. This happens at a higher temperature - 100C or so. The physical pressure from the steam will disrupt the integrity of the local cells, and the matrix will appear cloudy

c) Maillard reactions occur and the bacon browns. Maillard reactions happen at all temperatures, but are temperature dependent, so only happen at reasonable speeds quite hot.

I don't think that the protein denaturing has much to do with the colour change in the fat, but it is why the bacon shrinks in the pan.

[Rachel Perlow]

Huh, I thought the bacon shrunk because most of the bacon is fat and most of the fat melts out during cooking, leaving the protean (and quite bit of fat) behind.

[jackal10]

Huh, I thought the bacon shrunk because most of the bacon is fat and most of the fat melts out during cooking, leaving the protean (and quite bit of fat) behind.

Nope

The shrinking happens (at least with my bacon) long before the fat runs. What is exuded is the water and white scum...

[jsolomon]

jackal10,

I agree with you for most of what you said with a few minor variations:

Point a: You're right on the money.

Point b: Remember that the cell walls are also fat. By the time you get to 100C, they have long been melted and denatured. This is different for plants, but they have a different cellular structure, relying on cellulose enclosures around cells, so you need higher temperatures to rupture those structures. You are disrupting a supercellular structure when you get to the point that water is actively vaporizing "deep" inside the tissue.

point c: Maillard reactions are right on the money, but these are mainly anhydrous reactions. They don't happen quickly in the presence of water, and don't happen with much speed until you get to a screeching hot temperature of 300+ Farhenheit. This is why you sear at such a hot temperature. You can get these to happen in bacon earlier and more quickly if you really crank up the temperature, but then you'll scorch the bacon and have it done in an un-even manner. What is happening more are nitrate and nitrite reactions occuring with the myoglobin in the cells which give it the reddish color. Those happen at lower temperatures than the Maillard reactions. These start gaining appreciable speed at about 60 C, or a decent smoking temperature for... bacon and ham.

I personally think that as you increase the temperature, more of the fat leaves the structures and the proteins in the connective tissues are able to denature into tighter and tighter structures which is why the fatty areas shrink so much. It is well-known that meat shrinks during the cooking process, and it shrinks for several reasons: water loss, fat loss, dissolution of essential parts, and denaturation of proteins into tighter packed and less-ordered structures (which is why you can tell a cooked piece of meat from a fresh one by jabbing it with your finger... aside from the burns).

The maillard reaction explains the brown and the crispy, but there are many other things going on during that stage.

[OT] When I apply for entry into a food science graduate program, should I go into oenology, or something else? Anyone have suggestions, since this is the 'geek' thread? I'm applying to the University of Nebraska.

Edited with more information on Maillard.

Edited August 15, 2003 by jsolomon (log)

[mamster]

These answers are awesome, you guys. Cured pork jowl is delicious, and that's a fact.

[jsolomon]

These answers are awesome, you guys.  Cured pork jowl is delicious, and that's a fact.

I thought cured pork anything ( at least any proteinaceous parts, I shudder to think of cured pork brains, cured pork liver, or cured pork kidney ) was destined to be delicious.

[Katherine]

[OT] When I apply for entry into a food science graduate program, should I go into oenology, or something else?  Anyone have suggestions, since this is the 'geek' thread?  I'm applying to the University of Nebraska.

Edited with more information on Maillard.

Major in oenology, minor in pork products.

[jsolomon]

Major in oenology, minor in pork products.

That sounds like a political internship if I've ever heard of one ;)

[Really Nice!]

[OT] When I apply for entry into a food science graduate program, should I go into oenology, or something else?  Anyone have suggestions, since this is the 'geek' thread?  I'm applying to the University of Nebraska.

If I were going for an oenology graduate program I'd go to University of California Davis. From everything I've read, this is the place in the world to go to for an education in viticulture.

[jsolomon]

At the risk of continuing off topic, for all of its warts, I really enjoy the University of Nebraska, and there is quite a push to return the viticulture in Nebraska to its previous, pre-prohibition levels where our sandy soil and naturally stressful climates produced a vaguely remarkable level of wine.

Also, we have a good chemistry department whose resources I can draw on

[alanamoana]

just to move further off topic...does the protein in egg whites denature or coagulate?!

i think there needs to be much more bacon cooking in order to observe what exactly is going on...

someone please keep supply of tomato, avocado and lettuce nearby!

[Foam Pants]

To further science, I cooked some bacon today. I ate it. It was yummy. I forgot to observe anything else besides a tomato and some toast.

[Really Nice!]

To further science, I cooked some bacon today. I ate it. It was yummy. I forgot to observe anything else besides a tomato and some toast.

I ate bacon, therefore I am.

[Kouign Aman]

To expand further on the shrinking topic...

why does Costco bacon only shrink about 40%, but the bacon from the German butcher up the road shrinks ~75% ? (It looked like toy bacon when it was done).

Uncooked, I didnt notice any differences. Both were cooked the same way, tho in different weeks.

[DerekW]

why does Costco bacon only shrink about 40%, but the bacon from the German butcher up the road shrinks ~75%

Most if not all of the shrinkage is related to water loss, I think. Home cured bacon shrinks in the pan maybe 5%, if that. The polysorbate-pumped pigbits from the supermarket can reduce to 25% of their original surface area. Perhaps the German Butcher's bacon is not all that it might be?

[Kouign Aman]

Dunno, but it sure tasted good. Those little bits carried the same flavor impact as the much larger Costco strips. Kinda stunning to see them tho. They started 'regular' size, and were about the width of a piece of toast after cooking. They were streaky - nothing fancy like back bacon or anything.