Pickles preserve food with common salt and fermentation, and the added spices provide a tasty way to improve your health.
For thousands of years, humans the world over have used natural fermentation (or lactic acid fermentation) to preserve their vegetables in the form of raw pickles. Not only do the pickles taste great, but they offer health benefits too.
The Science of Pickling
All foods are continually assaulted by many kinds of microorganisms. When you put vegetables in brine for pickling, the water inside the vegetables flows out into the brine, making the pickles crunchier. The passage of water is by a process called osmosis.
Osmosis is the movement of water molecules through a selectively-permeable membrane – in this case, the membrane of the plant or vegetable cells. Water will move from an area of high solute (salt) concentration to an area of low solute concentration. In this case, the salt solution has a lower water concentration than the water inside fresh vegetables, so water will flow out of the vegetables. This process goes on until an equilibrium is achieved.
The following figure shows a similar effect when sugar solution of varying concentration is separated by a semi-permeable membrane.
When cucumber is immersed in a brine solution, the water leaves the cucumber in a brine solution and becomes shriveled, owing to osmosis. Later, another process called diffusion causes the salt molecules to diffuse back into the cucumber, and this is what gives the pickle its salty flavor.
Diffusion is the movement of solutes, like salts or dissolved sugars, from an area of high solute concentration to an area of low solute concentration. Diffusion is behind the marination of a food product.
Brining or pickling preserves food from micro-organisms. At a certain optimum salt concentration, lactic acid bacteria grow more quickly than other microbes. As lactic acid bacteria grow in the pickle jar, they digest sugars in the cucumbers and produce lactic acid that controls the spread of spoilage microbes. Also, by gobbling up the sugars, lactic acid bacteria remove a potential food source for bad bacteria. Thus, the spoilage-causing microorganisms do not survive, leaving lactic acid bacteria to colonize your cucumbers.