Some commercial jams state on the label that they contain "no preservatives", or are "preservative free". As I understand it, jam is a type of fruit preserve. Like most fruit preserves, it is protected against bacteria and mould before opening by the canning effect, and protected to a lesser extent against bacteria once opened, by its high sugar content (typically > 50% by weight).
Jams that I have seen labelled in this way also usually list citric acid as an ingredient, which commonly used as a food preservative.
My assumption is that food companies can get away with this labeling because sugar is required to activate the pectin during manufacturing, and citric acid can be said to be required for flavouring purposes.
My argument is that although jam wouldn't be jam without the gelling effect of the activated pectin, it also wouldn't be jam if it wasn't self-preserved after opening. It seems wrong to claim that sugar is not a preservative when used in jam, just because it has another function. It would be like claiming that full-cream milk is "fat-free" because the fat it does contain is required to make it appear white instead of having a blue tinge.
If another edible chemical that could activate pectin (but didn't have a preserving effect) was used to make jam, then would a manufacturer not get away with labeling the jam as having no preservatives, if sugar was added solely for the purpose of preservation?
I have not mentioned taste as a another function of sugar in jam because I don't think it is a relevant fact to consider. Jam tastes sweet because it is made with sugar for the reasons stated above, not because sugar is added to make it taste like jam.
Is "no preservatives" in jam a legitimate claim, or a marketing trick?
I have not researched the types of preservatives that are added to commercial jams that do not display the "no preservatives" claim, but I would be interested in this information if anybody knows.