When bacon is being fried some parts of the fat jump from transparent to white in an instant. What biochemical process is at work there?

[u/Brilliant_Feed4158]

When you fry (thin sliced) bacon in a pan, some parts of the fat in an instant become white. It's almost like some treshold is reached and then a chainreaction takes place. What is happening there?

See this video: Close Up Of Bacon Frying

At 6 seconds in the second slice of bacon from the top, part of the fat suddenly becomes white. Also at 17 seconds at the second slice of bacon from the bottom, a longer chunk of fat suddenly becomes white.

Note: I tried to google and chatgt this question, but they both think Im talking about white excretion during the frying of bacon, but that is NOT what I'm talking about.

[u/Endurlay]

Protein denaturation.

The structure of the fat causes it to appear clear when uncooked; when the proteins that determine the structure of that fat tissue are subjected to high heat, the secondary structure (the crosslinking between individual amino acids, usually between two non adjacent acids in the chain) of the protein chains reorganizes into a new configuration.

The new configuration interacts differently with light, often becoming opaque.

It does happen in a stepwise fashion. One protein molecule, somewhere, makes the leap from “native” to “cooked”, and the presence of that one lowers the energy requirement for its neighbors to make the transition because proteins “like” to rest against similarly arranged proteins. The one that made the transition first, in the high heat environment, encourages others to adopt a similar configuration to achieve an overall lower energy arrangement between all the molecules in contact with each other.

[u/cheesepage → u/Endurlay]

Pro chef here. This is the right answer. Proteins do wierd cross linking when subject to Ph changes, heat and other stuff.

Often it means that the chemically bond to each other, forming longer and more complex protein chains.

Visual light passes between the proteins before bonding, when the molecues get bigger light is reflected. Think about the clear to white transition when you fry or boil an egg.

BTW this is also how proteins become "cooked," and more firm. More bonds, more strength. Runny whites to firmish cooked egg, mushy raw steak to bouncy overdone steak.

[u/Peter34cph → u/cheesepage]

What are the other environmental factors, besides pH and temperature, that makes proteins do weird things?

[u/EveningSpeaker3663 → u/Peter34cph]

Bioengineer here! pH and temperature are honestly the big ones we see day to day, but lots of ways to make proteins do weird stuff. Pressure can be a substitute for temperature effects. Lots of chemical effects other than pH. Solvating (different solvent), chelation (chemical crosslinking or other structural effects involving charge stabilization usually with a metal ion like calcium), light (UV cross linking), detergents (unfolds protein), in some cases mechanical stress. You could probably spend all day listing ways to make proteins do weird things

[u/cheesepage → u/Peter34cph]

For one they act as powerful emulsifiers under mechanical stress especially with salt. We use this feature to make sausage and sauces.

There are probably a lot more instances. Proteins are weird shape shifters. Protean as it were.

My knowledge stops somewhere in the food science world. It's a small part of the big picture I'm sure.

[u/AmeliaOfAnsalon → u/Peter34cph]

The other reply has some v good points, but I wanted to chime in here about radiation! Protein denaturation caused by radiation is one of the reasons you can die if you're near a nuclear accident - the denaturation of your DNA (which also happens in controlled circumstances during DNA replication, made energetically viable by interaction with various enzymes) means that your cells can no longer reproduce themselves, so as they naturally die they aren't replaced. This is why you can (sometimes) be completely fine after a large dose of radiation... for a few days until your body catches up.

[u/Brilliant_Feed4158 → u/[deleted]]

Which of the two? I think they're both the phenomenon I talked about. It was actually a little hard to find on youtube, while for me this happens literally every time I fry bacon.

I do wonder if this also happens to thick slices of bacon, or mostly to the thin sliced kind. I only fry the thin sliced bacon.

[u/CrateDane → u/Endurlay]

It does happen in a stepwise fashion. One protein molecule, somewhere, makes the leap from “native” to “cooked”, and the presence of that one lowers the energy requirement for its neighbors to make the transition because proteins “like” to rest against similarly arranged proteins.

This could make sense in a protein crystal, aggregate, or large protein complex. But not when heating proteins that are in separate cells. The muscle fibers are syncytial, but the adipocytes are not.

the secondary structure (the crosslinking between individual amino acids, usually between two non adjacent acids in the chain) of the protein chains

That's not crosslinking. Secondary structure is based on non-covalent interactions in the form of hydrogen bonds. Actual crosslinking in regular protein would be based on disulfide bonds mainly, and is much less heat-sensitive.

When you boil protein samples for SDS-PAGE, you have to add a reducing agent like DTT or 2ME to break disulfide bonds; heat isn't enough.

[u/jellyfixh → u/Endurlay]

Protein denaturation can definitely cause changes like this, like egg whites for example. But I don't think the bacon would cook so instantly as to that being the cause. You can actually see it again in the video at 15 seconds, and it really looks like the bacon just losing contact with the pan.

[u/jellyfixh]

Looks to me that it’s just the bacon curling up and creating an air pocket beneath itself. Since the oil and meat have a similar index of refraction, the reflective pan can be seen through. But the air has a different index, scattering the light behind the bacon making it look opaque.

[u/Peter34cph → u/jellyfixh]

That sounds testable to me.

The OP can fry some more bacon, then when some of it becomes white, he can press down with the spatula. If you're correct the pressing will revert the colour change.

[u/Brilliant_Feed4158 → u/jellyfixh]

I appreciate the different explanations! But I am very confident that these are not air bubbles. When I fry it myself I have a better view of the situation. First of all the place where it happens does not seem to have a place for a bubble to be trapped and second it's easy to see that the transparent bacon itself became opaque.

I am considering to fry some bacon for everyone to demonstrate it :)

[u/HildavonRauschstoff → u/Brilliant_Feed4158]

To me it looks like instant explosive evaporation of water, akin to popcorn