Salt dries out food primarily through a process called osmosis. This is a natural phenomenon where water moves from an area of high concentration (inside the food) to an area of low concentration (the salty environment surrounding the food).
Understanding Osmosis
Salt, composed of sodium and chloride ions, readily attracts and binds with water molecules. As Fennema (1996) and Potter and Hotchkiss (1995) explain, this association significantly reduces the water activity within the food. When you sprinkle salt on food, the high concentration of salt on the surface creates a difference in water concentration between the inside of the food and its surroundings. This osmotic pressure draws water out of the food and into the surrounding salt, leading to dehydration.
Several sources confirm this mechanism. The Los Angeles Times archive article from 1985 points to osmosis as the foundational principle behind salt's drying effect. Similarly, Reddit threads and other articles reiterate that salt draws moisture through osmosis, leading to a drier end product. For example, curing egg yolks, a process detailed in Justine Doiron’s blog post, uses salt to extract water through osmosis as a key step.
Practical Implications and Examples
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Meat preservation: Salting meats before cooking (like dry-brining a turkey, as explained on The Kitchn) draws out moisture initially. However, this moisture is then drawn back into the meat by osmosis, ultimately enhancing flavor and texture. Incorrectly done this approach can lead to the dryness mentioned in other resources, such as in the Quora discussion on sous-vide cooking.
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Food preservation in general: The drying effect of salt is a major reason for its use as a preservative. By reducing water activity, salt inhibits microbial growth and extends the shelf life of food. A Reddit user points out that this drying effect alongside creating a hostile environment for microorganisms is how salt preserves food.
The amount of salt and the length of time it's in contact with the food determines the level of drying. Over-salting or prolonged contact can lead to excessively dry food, which is why articles such as one on the Wine Berserkers forum discussing prime rib preparation emphasizes caution regarding pre-cooking salting.
