Insta Cure or Prague Powder #1 as it is also known is a proportionate measure of salt and nitrite regulated by the FDA and USDA and is necessary to help prevent food poisoning. This used in curing sausage an is not abosolutly nessesary to make jerky but it is a preventative measure and will allow the jerky to have a longer shelflife.

The jerseyhunter provided a link to The Sausage Maker who cares Insta Cure #1 and below is another link that carries the same thing calling it Prague Powder #1.

Eldon's Sausage