On food and cooking the science and lore of the kitchen ( PDFDrive ) 230

Though the average Chinese consumes only a third as many eggs as the average American, and though most of those eggs are chicken eggs, China is renowned for its preserved duck eggs, including the “thousand-year-old” eggs These and plain salt-preserved eggs come from the duck-rich southern provinces, where they made it possible to transport eggs to distant markets and store them for months during the off season The proteins and membranes of chicken eggs are less suited to some of these treatments Salted Eggs The simplest method for preserving eggs is to treat them with salt, which draws the water out of bacteria and molds and inhibits their growth The eggs are immersed in a 35% salt solution, or coated individually with a paste of salt, water, and clay or mud After 20 or 30 days, the egg stops absorbing salt and reaches chemical equilibrium Strangely, the white remains liquid, but the yolk at its center becomes solid The high levels of positive sodium and negative chloride ions actually shield the albumen proteins from each other, but cause the yolk particles to agglomerate into a grainy mass Salted eggs, which are variously called hulidan and xiandan, are boiled before they’re eaten Fermented Eggs A second kind of preserved egg, little seen in the West, is made by covering gently cracked eggs in a fermenting mass of cooked rice or other grains mixed with salt: in essence a concentrated and salty version of sake or beer Zaodan mature in four to six months and take on the aromatic, sweet, alcoholic flavor of their surroundings Both white and yolk coagulate and fall out of the softened shell Such eggs can be eaten as is or cooked first Pidan: “Thousand-Year-Old” Alkali-Cured Eggs The most famous of preserved eggs are ... rice or other grains mixed with salt: in essence a concentrated and salty version of sake or beer Zaodan mature in four to six months and take on the aromatic, sweet, alcoholic flavor of their surroundings...liquid, but the yolk at its center becomes solid The high levels of positive sodium and negative chloride ions actually shield the albumen proteins from each other, but cause the yolk particles to agglomerate into a grainy... surroundings Both white and yolk coagulate and fall out of the softened shell Such eggs can be eaten as is or cooked first Pidan: “Thousand-Year-Old” Alkali-Cured Eggs The most famous of preserved eggs