Color change

In a clear bottle on a lit shelf, color is the first thing to fail and the first thing a customer notices.

Color is the least stable thing in the bottle

Natural colors in an acidic, aqueous, light-exposed product have every condition working against them.

And unlike flavor, which degrades quietly, color change is visible through the glass from a meter away.

Anthocyanins

The reds, purples and blues: berries, hibiscus, red cabbage, purple carrot.

Two behaviors to know. They are pH indicators, so their hue shifts with acidity, red in acid, purple to blue as it rises, which means a pH drift is visible as a color change.

And they degrade with light, heat and time, usually towards brown.

So a bright pink drink turning dull brown over three months is the expected behavior rather than a surprise, and a shelf life has to be set with it in mind.

Browning

Enzymatic browning in fresh juice, which is the apple going brown, and is stopped by heat or by acidity.

Non-enzymatic browning over time, accelerated by heat and by sugar, which is what turns a pale juice amber in storage.

Oxidation, through headspace and through permeable packaging.

Controlling it

Amber or opaque packaging, which is the cheapest and most effective single change and which gives up the visual appeal of the product.

Minimal headspace and a low-oxygen fill.

Cold storage.

A shorter stated shelf life set against the color rather than the flavor, because color usually fails first.

And a reference bottle from an approved batch to compare against, so a drift is measured rather than argued about.

References