What it does
Oxidation runs as a chain reaction in which one radical creates the next. An antioxidant interrupts it, either by donating a hydrogen and stopping the chain, or by chelating the metal ions that start it. Some materials do one and some do both, which is why they are often used in combination rather than alone.
Where it works
Any product where fat oxidation, rather than microbiology, is what ends shelf life. Cooked and cured meat, coated and fried products, nut and fat based fillings.
Where it does not
Several carry flavour of their own, and rosemary extract in particular has to be deodorised or it will be tasted. They are also generally less potent than the synthetics they replace, so an equivalent effect needs a higher level. And no antioxidant reverses oxidation that has already happened; applied late, it does nothing.
What it interacts with
Chelating agents, synergistically. Light, heat and oxygen exposure in packaging, which decide how much work it has to do.
