When stock goes off-condition
Updated
Everything in a bottle is moving, and in a live product some of it is moving fast.
A drink ages in several directions
Carbonation leaves, or increases.
Color fades or browns.
Flavor oxidizes and flattens.
pH drifts, usually down in anything fermented.
Alcohol rises, in anything live.
Sediment forms.
Six clocks, and they do not run at the same speed.
What to check
Retained bottles on a schedule, both refrigerated and deliberately warm.
Carbonation and pressure, especially on the warm ones, behind a screen.
pH and Brix, which together tell you whether fermentation is continuing.
Alcohol, on the warm retains, at the end of the stated shelf life, the number the whole legal position rests on.
Appearance and taste against a reference.
And the closures, for weeping or loosening.
How long it keeps
An unpasteurized refrigerated juice is days to a few weeks.
A live fermented product is weeks to a few months refrigerated, and the limit is usually pressure and alcohol rather than flavor.
A pasteurized or filtered product in glass is many months.
Establish yours from the retained samples rather than copying a competitor's date, because their process and package are not yours.
Rotation
Strict first in, first out, which needs a date code on the bottle.
Cold, dark storage, which for a live product is not optional.
And do not ship stock near the end of its life to a wholesale account, where it will sit further and become their opinion of the range.