You need to freeze the hog meat for 3-5 weeks before you grind or freeze the pre ground for the same.
Note that freezing will not kill them, but it will prevent the Trich from attaching to you. Keep in mind that the 20 days start when the core of the meat reaches 5°F, which can actually take several days in most freezers. That’s why I freeze for at least a month with bear or wild boar I plan on making into salami, just to be sure. All of this applies to T. murrelli also.
Salt lowers the water activity of the meat, which means that less water is available to the larvae. The fermentation bacteria produce acid which also lowers the water activity while the acid wrecks the metabolism of the larvae which, like many living things needs to be close to pH 7 (neutral) to work properly. All of that, plus the enzymes, toxic oils from the herbs, etc. plus nitric oxide from the nitrate, beat the hell out of the trich.
These processes going on should prevent you from actually getting trichinosis, which is why people have been safely making salami with wild and domesticated pigs for 2000 years. But you need to be a careful curer of meats and not take shortcuts.
The key figure here is at least 2 percent salt by weight of the total meat and fat. So if you make a 5-pound batch of salami, as I often do, you will need at least 45 grams of salt to be totally safe. I tend to use a bit more, like 50+ grams to get close to 2 1/2 percent by weight.
As Dave mentioned.
Trichinella spiralis. Humans and other animals may be infected by eating raw or undercooked meat of infected domestic pigs, wild bears, wild pigs, or other meat eating animals.
There is not just one trichinella parasite. There are many. Here in North America we have five major species: Trichinae spiralis, which is the most common and hangs out with pigs for the most part; then T. nativa, T-6 and T. murrelli, which are almost always found in wild game — chiefly bears.
You can also kill any trichinae parasite by heat. And the “kill temperature” is cooler than you might think. The origin of the odd USDA mandated internal cooking temperature of 160°F appears to be the government trying to account for inaccuracy and idiocy. (That temperature is more relevant for salmonella than trich.) The actual temperature that kills the trichinella parasite is 137°F, which happens to be medium-rare.
