The quality of caviar obviously depends on the origin and the type of preparation, as well as the care taken during the preparation stage.
Connoisseurs prefer fresh malossol, which contains a maximum of 5 percent salt by weight. Borax, which acts as a preservative, is added in France to caviar with low salt content (not in the United States, however, where borax is an illegal food additive).
Specialists read the information printed on the side of the tin when the caviar was packed. This indicates the number of fish, the number of tins filled with roe from the same fish, and the color classification of the caviar' (light, medium, dark).
The second quality found on the market is salted caviar, which contains up to 8 percent of salt by weight. This type of caviar is generally destined for the American market, where borax is prohibited by law.
The third quality is pressed caviar, made from soft, broken or over-mature eggs. They are placed in highly salted, hot brine and shaken until the caviar is no longer milky. This salted caviar is then placed in cheesecloth and put in small oak barrels coated with paraffin. The caviar is then pressed to remove the excess liquid. This type of caviar used to be so thick that it could be sliced with a knife, but pressed caviar today is softer and can be spread like jam. Russians prefer the strong flavor of this caviar, which is also recommended for cooking.
Finally the last quality is pasteurized caviar: it is vacuum-packed in small glass jars three to four hours after the fish has reached the processing plant. The pasteurization process, which involves heating the eggs, alters the flavor of the caviar, but it can then be stored for a longer period of time.