Eli5: If salt is used to cure and preserve food why is ocean water full of bacteria?
In: Biology
Bacteria needs water. Salt absorbs water and makes it harder for bacteria to absorb it. This is how we use salt to preserve food. But there is a lot of water in the ocean. There is not enough salt to make the oceans dry.
Bacteria come in a lot of varieties, some of them thriving in extreme conditions–also, the relative amount of salt and *moisture* in each case is quite different. Regardless, the bacteria in salt water is likely not the same bacteria you’re trying to avoid with food preservation, nor is it an indefinite preservation method to my knowledge. But really, I think the moisture part is a huge part of the equation–life generally depends on water. If it can’t bring its own or collect it from its surroundings, it’s unlikely to thrive. Add to that most microorganisms aren’t adapted for extreme salt conditions, and there you go.
High enoug salt levels kill bacteria, The brine, water and salt mixture, you use if you what long time persevation is around 20% for fish, compare that to seawater that is around 3.5% salt. Brine can be around 26% salt by weight at room temperature, that is the level you can reach if you preserve it weet.
If you preserve meat you surround it with salt that in large part draw out water. Here is a example of how it is done, the salt remain solit around the meat [https://www.youtube.com/watch?v=vg4OIFd5-aA](https://www.youtube.com/watch?v=vg4OIFd5-aA)When you eat it it will tase very salty, letting it rest in water to rehydrate and remobe salt is a good idea. It was in part for practical reason but alos to make it taste less of salt often cooked in a stew. Add starchy vetibles like potatoes and they will absorbe water, the contain very little salt to begin with and make the dish overall less salty.
The water removal is a important part of the reservation, jerky is dried meat that is preserved by remove the water. Bacteria need water to live, put a pice of bread in a plastic back and another on a plate out in the open. In normal indoors condition the bread out in the open will dry quickly and preserved because there is not enough water for any bacterial or fungal growth. The bread in the plastic bag will likely get mouldy. If you look at you pantry there is a lot of dry stuff there with very long shelf life, it is preserved primary because of the low water content. Mix flour and water and keep in in the open and you quicltu see growth of stuff in it
When you preserve something using salt, you use massive amounts of it. Brines are often 20% (by weight) salt or more, some fish are dried out by just packing salt around them, etc. The ocean is around 3.5% salt by weight (this obviously varies by where you look and when.)
For comparison, the Dead Sea (guess how it got its name) is about 34% salt by weight, and almost nothing can grow in it. Even microscopic life can barely survive there.
Essentially, while the sea IS salty, it’s nowhere near salty enough to prevent bacteria from growing in it. It is, however, salty enough to seriously harm you if you were to drink seawater rather than actual fresh water.
It comes down to concentration. The salt kills bacteria by creating such a concentration gradient it pulls the water out of the cells and kills them. Thus the curing process.
The oceans however do not have salt that is that that high thus the gradient is not high enough to distort the bacteria that are adapted to the. The salt concentration in the ocean is below 3.5% or 35g/L.
Thst said there are hypersslinated lakes in the world that nothing but specifically adapted bacteria live in. There lakes can be over 40%salt content in the water or 400g/L. And they do just fine. This is likely due to adaption of the soecies over time and likely have processes to retain osomtic balance but i would need to dig into them specifically to see what is going on. Extremophiles are fun.
Like bane, these bacteria were born in the salt, molded by it. We merely adopted the salt.
There’s more salt, by percentage, in the food preserved via salting.
Like, ten times more. Food preserved solely by wet salting is very salty almost inedible. Food often times is salted and dried (as a serendipitous byproduct of salting) which both work together to reduce the water activity of food.
As in most things it is the amount of something that makes the poison.
Latest Answers