I have a recipe with these ingredients - tomato, relish, dill pickle, mustard, peperoncini, onion. I need to can the recipe but dont want the ingredients to cook and become mushy.
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DIY canning without a trusted recipe can be risky, especially when vegetables are involved... My first instinct is to suggest that you scour the web and/or the local library's cookbook section for tested similar recipes as I'm sure they're out there; what you describe is very similar to Italian giardiniera.
Hmm, sorry must've missed "dill pickle" in the ingredient list when I thought giardiniera... Scratch that as a starting point. Nevertheless, still highly recommend you take the time to find an established recipe.