What is vegetable broth's problem?

[ProfessorGAC]

11. A Few Things

First, the 10 days a manufacturer puts on the label has at least a 100% safety marging built in.
Meaning that, sealed & refrigerated, it's actually good for 20 days, as a minimum.
Second, with a clear broth it's easy to detect early spoilage. If it's getting cloudy (beyond what's reasonable for a high salt liquid that's cold)); if in doubt, let it come to room temperature.
Now, I've checked pH of broth and it doesn't change after the box is open. Due to lactic acid formation by bacterial respiration, pH drops as bacterial content rises. Broth should be around a 6.5. If it goes below 6 there's too much bacteria.
But, by that time the broth would start to take on an odor (a bit sour & acrid, in part from that same lacticacid(), so you don't need to check pH. I just have the hardware.
So, sight & nose will tell you what you need, if you go past that 20 days.