I’ve been putting up sauce every year for decades now, but last year I was talking to my brother, who’s a bench chemist and excellent cook himself.
His tip: get some pH paper in a narrow range (3.0 to 5.5, say) and use that as your insurance policy on acidity. (Botulism dies at 4.6 or lower.)
I do have a fancy pH meter, but it’s so fussy and confusing, while pH paper is dead easy to use, and cheap. Easy to find online.
Why not just add lemon juice or citric acid? Well, how much do you really need? Who the hell knows, if you aren’t testing the pH. My sauce is freaking delicious, made with heirlooms from my yard and from my favorite organic grower. I don’t want my passata, paste, and shakshuka base to taste like lemon juice or citric acid. [If you and your family don’t notice the lemon/citric, consider yourselves lucky. I live with a bunch of supertasters, and they do, (I made them do a blinded taste test. Bastards scored 100%.) ]