Wine substitutions for homemade salami

Substitution in preserved foods are generally considered unsafe. Food chemistry is a complicated affair, and cooking is inherently imprecise. Sure, you can find a way to reduce the pH to that of the original recipe. But a salami is a fermented food. Your pH might be the same, but other things will change, for example the composition of the available sugars, and you can catch a different strain of bacteria. Safe preservation recipes have either been extensively tested in a lab, or used for centuries. Making a small change can destroy the delicate balance which leads to a tasty, safe food.

The solution here is to look for another recipe, one which is safe but does not contain wine. For something as risky as cured meat, I'd suggest not getting some random recipe off the Internet, but choosing from a book, or maybe from the blog of a known, respectable author. This way, you get both good taste and safety, things which are hit-and-miss when making your own substitutions.