re: How do restaurants get away with not refrigerating ketchup?

I was always told that because it had such a high ph, it didn't spoil quickly at all.

They also just refill those bottles at the end of every night, so that ketchup at the bottom is probably old as dirt.

When it starts to spoil, it fumigates and if you open one under the right circumstances, it'll spray ketchup out like a shaken up soft drink.