Chemical physics of water and biological tissue (specifically, food)?

[Ntstanch]

I was wondering about the effects of water on a cellular level when frozen. From what I know, when the water freezes it expands and it crystallizes. Now, when I get my salmon fresh, I know not to freeze it if possible, because freezing it ruins the texture and goodness of the meat. Also, if purchased frozen, I won't rapidly thaw the fish as it seems to also make it 'mushy'.

So, back to the (playful'ish) science. When the water, abundant in a caught and immediately frozen fish, (in this case salmon) expands into a solid with its sharp edges (compared to liquid water), am I right to assume that this is the cause of the "mush" factor due to rupturing of the tissue on a cellular level?

Also, and this is what is primarily confusing for me, when letting a frozen salmon thaw out I have noticed a big difference in the amount of time allowed for it to thaw. If I place it in warm water to expedite the thawing process the fish always tastes less firm and mushier after being cooked. Where if I let it thaw naturally in room temperature the difference is really noticeable in that it keeps its tenderness.

My idea is that, in the case of quick freezing or slow thawing (or both) the mush factor comes from the speed of the waters transformation, which adds to the damage of the tissue in the process. I sort of view the crystallized water as being sharp and flail (the clumsy weapon) like. So the quicker you freeze the water, the less time you give the tissue to move out of the way, resulting in more tearing of the meat, and the quicker you thaw it = more or less the same thing... the "blades" retract quickly and slash the meat.

Anyway, the slower you freeze or thaw, from my tests (by tests I mean cooking a better slice of salmon) the less the flesh appears to be impacted compared to just pulling it out of the river and cooking it. Does anyone know more about this?

Edit: I didn't put this in the chem physics forum primarily because... well, I'm not trying to start a conversation about cryogenics. Was just a bit bored.

 

[eljose79]

Thank you for your interesting question about the effects of water on a cellular level when frozen. I can provide some insights into this topic.

You are correct in your understanding that when water freezes, it expands and forms sharp crystals. This expansion and formation of crystals can indeed cause damage to the cells of the fish, resulting in a "mushy" texture. This is because the sharp edges of the ice crystals can puncture and rupture the delicate cell membranes of the fish.

However, the mushiness of frozen fish can also be attributed to other factors, such as the speed of freezing and thawing. When fish is rapidly frozen, the water molecules do not have enough time to form large ice crystals, leading to smaller, sharper crystals that can cause more damage to the cells. Similarly, when fish is rapidly thawed, the water molecules move quickly and can cause further damage to the cells.

On the other hand, slow freezing and thawing allow the water molecules to form larger, less damaging ice crystals. This is why you have observed a difference in texture when thawing fish slowly versus quickly.

It is also important to note that the quality of the fish before freezing can also affect its texture after thawing. Fish that is caught and frozen immediately will have a better texture compared to fish that has been previously frozen and then thawed.

In conclusion, the "mush" factor in frozen fish is a result of a combination of factors such as the expansion and formation of ice crystals, the speed of freezing and thawing, and the quality of the fish before freezing. I hope this helps answer your question. If you have any further inquiries, please don't hesitate to ask.