We commonly get asked this question - So I wanted to provide a succinct answer for those that are interested. The following is an example of a "Russian-Style" for hand processing caviar. I mention this because there are multiple styles for turning ordinary roe into caviar. Additionally, this method is primarily used for Sturgeon roe.
First, the female sturgeon is caught and the entire egg sack (ovary) is removed. The sack is then placed on a mesh netting and lightly rinsed with water. This clears the eggs of an unwanted particulates. The eggs are then gently rubbed across the mesh netting, which is key in separating the eggs from the ovary membrane itself. The eggs are then rinsed again with water and are now ready for salting.
Salting the separated and cleaned roes is also referred to as "malossol", which translates to "little salt" in Russian. In the caviar industry, "Malossol" is usually reserved for caviar that contains 3% to 5% salt content. Generally, higher quality eggs receive less salt than average and low grade roes, as the higher grade roes need less salt (additive) to influence the shape and texture of the roe.
After the roes are lightly salted, they are left to soak in the salt for several hours, after which time they are again lightly rinsed to remove the salt brine. Salt is used as a natural preservative for the eggs, and to give the eggs substance and taste. Unsalted roe are tasteless, and lack a rolling texture and firmness that pops in your mouth, which is quintessential to caviar. Thus, salting is a very important step in producing true caviar. Alas, the roes have now become "caviar", and are ready to be packed for consumption.
Some producers, namely of the Iranian style, also add "borax", which is a preserving agent meant to extend the shelf-life and freshness of the caviar, and influence its taste and texture. More information on borax next week.
Additionally, some caviar producers use a process of "aging" the caviar. These producers believe that although caviar should normally be eaten as a fresh product, there needs to be a brief period of aging (anywhere between 5 and 14 days) to allow the salt to truly soak into the roes and influence both taste and texture.