Food Flavourings

Loss of desired attributes during applications, and sometimes change in flavor notes; one one becomes dominant while the others are weakened.
Therefore its pretty obvious that the flavor is not up to the task...

What is it you would like to know?

I want to know the ones suitable for disposal

Thanks Roy

Are there methods to prove this scientifically?

You're getting academic for flimsy reasons,,, You want real details then contact your flavor supplier and ask them about the information relevant to your needs...
..

I suggest you always keep standard sample in cold /Air conditioned room when you produce/buy a flavour and if you want to revalidate after completion of shelf life you just compare the standard with sample which you want to revalidate.
There is no technical method to revalidate- you need to identify the difference in taste and smell. you can do it with triangle method to be sure.

Very clear 👌thanks 😊

sometimes it is good to put questions as what it is aimed for..Here i am not sure may be you synthesized the chemical and you are just looking for its quality or shelf life based testing.
In fine chemicals industry, they perform very simple methods as having a 'standard' of the same chemical from the competitor and do necessary tests like 'triangle' test or others. Also color, changes in aroma are all factors to check over months or years.

Understood
Lots of appreciation

Volatiles like acetaldehyde, added for freshness effect decrease over the shelf life. Acetal reactions with Propelene Glycol occur over time and if any heat is used to dissolve crystals during modification. Esters interact with each other, causing interesterification, often referred to as Tutti Frutti effect, Discolouration or increase in colour can also happen. Oxidation of citrus oils occur and coffee flavours degenerate over a short shelf life.