Whether you buy your sausage meat, raise and butcher your own livestock, bag your own game, or catch your own fish, there is one cardinal rule that must be followed faithfully. That is, all meat, every source of protein, must be very, very fresh. Ground up meat has a proportionately greater surface area than the same weight before it is ground. The more surface area, the larger the breeding ground for bacteria. Bacteria thrive at temperatures between 40 and 140 degrees. This means that your fresh ingredients must be kept cold as much as possible so that bacteria will not have a chance to reproduce and taint the meat. Keep it cold, clean and covered until you are ready to make your wurst!