Salting and salt brine — the chemistry behind preservation

You have already learned that intestines are preserved, typically by salting, to become shelf-stable for storage and transport. But why does salt actually preserve? The answer lies in basic food chemistry, and if you understand the principle, it becomes easier to understand why this particular part of the work must be done carefully every single time.

§Osmosis, also called fiberglass pest shows up as blisters under the gelcoat when water penetrates through primer and gelcoat and collects in voids in the laminate.

Salt draws water out of the casing's tissue through a process called osmosis: water travels from a place with low salt concentration to a place with high salt concentration until there is balance. The result is that the casing loses some of its water content. What microorganisms like bacteria need to grow is free water — what food chemists call water activity. When salting lowers water activity sufficiently, bacteria simply don't get the conditions they need to multiply, and the product becomes far more durable.

§Dry salting versus brine

In practice, preservation with salt can be tackled in two ways. In dry salt curing, the guts are packed directly in dry salt, which draws liquid out of the gut and forms its own brine in the process. With salt brine, the guts are instead placed in a ready-made, strongly salted liquid. Both methods are based on the same principle — raising the salt concentration around the gut — but they place different demands on controlling time, temperature and storage, and the company chooses the method based on what suits their production and logistics best.

• 01Dry salting: the intestine is packed in dry salt that draws out water and forms its own brine.
• 02Salt brine: the casing is immersed in a ready-made, heavily salted liquid.
• 03Both methods reduce water activity and inhibit bacterial growth.
• 04Temperature during salting affects how fast and how evenly the process proceeds.
• 05Too little salt or too short a time gives insufficient preservation and risk of spoilage.

§Temperature, time, and even distribution

Salt works slower at low temperatures, but low temperature in turn keeps bacterial growth down while the salting gets time to do its job. Therefore it is not a matter of indifference how cold it is in the room and how long the casings have time to lie in salt or brine. Equally important is that the salt is distributed evenly — if there are places on the casing that the salt does not reach properly, those places can become a weak point in the preservation.

§From salted casing to stable product

When salting is done correctly, you have a product that can withstand the journey it often must make—from the cleaner, through export, and on to the sausage factory that finally uses it. If you understand the chemistry behind it, it becomes clear why this part of the work isn't something you can take lightly: an error in salting can first show up far away from your own workbench when the product has long since been sent on.

§Desalination at the customer

Salting is not the end station for the casing — it is a temporary form of preservation. At the sausage factory that later uses the casing it is typically soaked and rinsed so it becomes supple and ready to be filled with farce. It is therefore important that the salting is neither too weak nor unnecessarily strong: weak preservation gives risk of spoilage in transit while unnecessarily hard or uneven salting can make the work harder for the customer when the casing needs to be prepared for use again.

Salting is far from a new invention — it is one of the oldest known preservation methods for animal raw materials and has been used long before the underlying chemistry with osmosis and water activity was understood. As a casing technician you thus continue a method humans have used for centuries, just supported by a modern understanding of why it actually works — and of the control forms and temperature requirements that today ensure it is performed uniformly every time.