I've heard of Indian dry mango pickles that are ~20 years old! I guess a product that is dominantly colonised by harmless bacteria is unlikely to be taken over by nasty things, unless it sports food that is tasty to harmful organisms and not friendly ones. Maybe the best defence is the dominant bacterium having eaten all the available sugars so that little further fermentation can occur (and the bottle won't explode)
When I was a kid, the pickles we bought would last 2-3 years in some cases - only typically being eaten at special meals like christmas, new years, easter, birthdays.
These days I wouldn't trust a modern shop bought pickle to last more than a couple of months before they start to look like they're growing fungus.
I don't know what changed, but something did, and commercial pickles these days do not stay safe to eat.
Yes! Fermentation of fresh foods with lactic acid bacteria increases the acidity of foods and hence the shelf life. As far as I know, though, you also have to add salt to suppress the growth of less desirable microorganisms.
Edit: You can skip the fermanation step by pickling your vegetables with a suitable vinegar. The taste will be much different though.
Yup, my understanding is that salt suppresses many bacteria, then the acid produced by lactobacteria (hopefully) suppresses botulism. Essential to ensure you have enough sugars to convert to acid! Test the pH in your ferments if you're giving them to friends!
Fermentation does a few things - it removes some of the excess sugars so other microbes don't have much to feed one, it changes the ph of the liquid so that again it is inhospitable to other microbes, and the mild alcohols can also inhibit other growths.
Wines can taste great (better even!) after years of storage, I would have not problem eating a well ages fermented ketchup.
"Fermentation was primarily developed for the stabilization of perishable agricultural produce."
https://www.sciencedirect.com/topics/food-science/food-ferme...