We talked the other day about how proteins are very long molecules that often come entangled together in a ball which is basically inedible and to be able to digest them we need to unfold (denature) them. Very often this process changes the appearance of food, for example in the case of fish and egg whites they become opaque, and we associate this change with the fact that they have been cooked.

While I was writing that post I read that, although the most common way to denature proteins is by heating them, there are other ways such us using vinegar or salt. This is why we think of food that has been preserved in salt or vinegar as cooked, even though they have never been exposed to high temperatures. Some examples are: anchovies in salt, pickles, Serrano ham, cured salmon, carpaccio, salted beef, etc. I did a couple of experiments to test in a small scale how this works.

In the first one I tested how vinegar can unfold proteins with an egg. I put a raw egg in a glass (this time without the shell 🙂 ) and covered it with vinegar. After a couple of hours I could already see how the white had become a bit opaque and also it stayed together rather than spreading and mixing with the vinegar:

Raw egg in vinegar.

Raw egg in vinegar.

Raw egg in vinegar after 2 hours.

Raw egg in vinegar after 2 hours.

Even though I changed the vinegar and waited until the next day, there was no further change in colour, probably because the vinegar cannot penetrate further in the egg. This explains the trick that I had heard of pouring a bit of vinegar in the water while boiling eggs to prevent the whites spreading everywhere in the pot in case an egg cracks. Of course one has to be careful with the amount of vinegar in this case not to alter the taste of the eggs.

The second experiment I did was on raw fish (in this case salmon). With just a thin layer of salt you can see (and feel when you try to tear it up with your hands) after an hours the change in colour and texture:

Raw salmon

Raw salmon

Salmon sprinkled with salt after 1 hour.

Salmon sprinkled with salt.

Difference in colour between raw salmon and salmon cured with salt.

Difference in colour between raw salmon and salmon cured with salt.

If you want to cure salmon at home with the purpose of eating it you should use a mixture of 50% salt and 50% sugar. The sugar is necessary because it feeds a type of bacteria which accelerates the process which breaks down the enzymes normally responsible to causing food to spoil. You can use this mixture to cure other kinds of fish or even meat. The length of time will depend on how thick is your slice. For a thin slice one hour is enough but if you want to do the whole salmon at once you will need 12-18 hours.

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