How to Preserve Food With Salt: The Science of Salt Preservation

If a time machine could take us back to Ancient Rome, we might find ourselves side by side with the artisans of the period, all intent on stuffing large fish into terracotta urns, in between generous layers of salt. Salting, as it is called, is a technique for preserving food that lives on and is still carried out using the same methods and processes. For the reasons we are about to discover, salt is actually able to preserve most foodstuffs for months and even years. At the same time, this method of preservation confers a unique and delicious flavour to food whose refinement derives from its high degree of salinity. What more can be said about an exquisite plate of herrings? And the tasty capers used to flavour a dish of pasta in tomato sauce? These are just two examples of how important salting is and why it is worthwhile finding out the secrets behind it.

How does salting preserve food?

Let’s start from basics: why does salt act as a preserve? To understand this concept, let’s consider a piece of meat placed in a terrine and covered with cooking salt. After a few minutes, we see the salt crystals “disappear”. In actual fact, they do not disappear: they simply absorb water to the point that they melt completely. No magic is involved here: it is a physical-chemical phenomenon called 'osmosis' whereby two solutions, which are brought into contact with each other, achieve the same degree of saline concentration and in order to reach a situation of equalisation, the water molecules in the meat simply relocate to our dear old salt grains. To simplify, we could say that the salt absorbs the water in the meat but, if you have a scientist friend, you can impress him by proving that you understand how osmosis works. Usually, however, a salt and water solution is used rather than salt alone: in this way we are sure that osmosis takes place over the entire surface of the meat.

Osmosis: the antidote to bacteria

Why is it so important for this to happen? Because, as you have already grasped, the function of osmosis is to dehydrate the meat, or whatever other food we intend to preserve. To dehydrate means to remove water, the most precious element of life, comprising the bacteria responsible for decomposition. Which is the exact phenomenon we wish to prevent. By removing water, we prevent bacteria from making our precious food go rotten! For a correct salting process, whatever raw material is involved, we must follow a few simple rules. First of all, we will use a highly concentrated salt solution. Ideally, we will take the amount of water necessary to completely cover the food and then we will add salt gradually, mixing as we go, until we reach the point where salt starts to deposit on the bottom. This is now a 'saturated' solution and therefore perfect for our purpose. Once the food has been immersed in the solution, keep it in the fridge for several days (depending on its type and quantity), closed with a stopper or a hermetic lid.

At the end of this period, change the brine if the food is to be kept in the liquid or dry it and cover with cooking salt. In the case of meat or other protein-rich foods, you may dry it and place it in an oven at a low temperature. For a superior result, a natural drying method is to be preferred: meat and fish lend themselves marvellously to being stored in a dry, well-aired place. When they are well dried out (several weeks are required), they may be enjoyed cut into fine slices and possible served with lightly toasted bread spread with a butter of excellent quality.

Common foods preserved in salt

Meat and fish are the most common foods preserved in salt, sometimes in accordance with local traditions that date back centuries.

For an everyday food that is still salted to extend its lifespan, look no further than ham. Salting is taken so seriously in the case of Parma ham, for example, that this step has to be done by a certified salt master. The ham is then cured for one to three years. To try this delicacy in all its saliferous glory, there is perhaps no better way than atop a parmesan wafer with figs.

As mentioned earlier, there is a storied tradition of using salt to keep fish from declining into stench. Take smoked salmon, for example. Of course the smoking itself plays a role in the preservation, but the fish must also first be packed in dry salt or soaked in a heavy brine prior to the rest of the process. Savour the salient flavours of this ingredient on potato pancakes with caviar, chives, and horseradish.

But meats don’t have a monopoly on salting. Did you know that, among many other non-meat items, you can preserve lemons with salt? Salted lemons are common in the cuisines of the Indian subcontinent and North Africa and will keep for up to a year. Use them to add a tart umami flavour to ice cream or homemade cheese.

Other ways to preserve food

Humans have been preserving food since ancient times and some of the oldest methods include drying and fermentation. More recent inventions, such as canning and pasteurisation, have a key role to play in modern food preservation and are now carried out on an industrial scale. There are plenty of options available to home cooks, however, including pickling, smoking and even burying, all of which acts to prevent the decay or spoilage of food so that it is fit for future use. Each method acts on the food in different ways. While salting and pickling remove moisture from foods like meat, burying removes light and oxygen and keeps the food at low temperatures.

For more tips and step-by step guides to some of the options available in home kitchens, check out this fascinating article on methods and techniques for preserving food.

If you’re interested in learning more about the science behind gastronomy, find out about the various methods of cooking vegetables here. Also, from savoury to sweet, caramelisation involves a reaction that turns a solid into a liquid substance. Find out more about that here.