By Harold McGee
In traditional caviar-making, sturgeon are captured alive in nets, stunned, and their roe sacs removed before they are killed and butchered. The caviar maker passes the roe through screens to loosen the eggs and separate them from the ovary membrane, sorts and grades the eggs, and then dry-salts and mixes them by hand for two to four minutes to obtain a final salt concentration between 3 and 10%. (Small amounts of alkaline borax [sodium borate] have been used since the 1870s to replace part of the salt, making the caviar taste sweeter and improving its shelf life, but the United States and some other countries forbid borax in their imports.) The eggs are allowed to drain for 5 to 15 minutes, filled into large cans, and chilled to 26°F/–3°C (the salt prevents freezing at this temperature).