my mother in law is an Italian immigrant (came here legally 50 years ago, took the test became American citizens)....she cans tomatoes every year and never uses lemon juice...just confirmed it with my wife who gave an emphatic “NO” to the lemon juice question...
I’ve been wondering about that. I raise heirlooms, which urban legend claims have higher acid content. My grandfather converted an old chicken coop into my grandparents first home, so I’m pretty sure grandma didn’t have lemon juice or citric acid.