By Harold McGee
Cooked sausages are heated as part of their production, and can be bought and eaten without further cooking for several days, or longer if they’ve been partly dried or smoked. But they’re often cooked again just before eating. They can be made from the usual mixture of meat and fat, or from a number of other materials that thicken on cooking. The French white sausage, boudin blanc, is made from various white meats bound together with milk, eggs, bread crumbs, or flour, while the black boudin noir contains no meat at all: it’s around one-third pork fat, one-third onions, apples, or chestnuts, and one-third pork blood, which coagulates during poaching to help provide a solid matrix. Liver sausage is made by cooking a blend of finely ground liver and fat. Manufacturers often use soy protein and nonfat milk solids to help thicken and retain moisture.