Most of us have a jar of jam at the back of our kitchen cupboard, but not many people realise they are storing it wrong. Jam tends to have a long shelf life but any exposure to heat will cause the sugars and fruit inside to become contaminated. 

It might be okay to store jam in a cupboard during the colder seasons, but as the weather heats up, the humidity can encourage bacterial growth which will make it spoil but can also ruin the taste. If you have ever open a jam only to discover it has gone bitter, watery or even mouldy, then you are storing it in somewhere that is far too hot. 

Jam contains pectin, a natural gel which helps thicken it, which will begin to break down when exposed to hot temperatures and cause condensation. 

The extra moisture will dilute the flavour of the jam to make it much thinner and even cause it to spoil at a faster rate.

How to store jam properly during warm weather 

Instead, Mark Davis, a storage expert from Fridge, has shared jam will last a lot longer it you refrigerate it properly. 

Mark said: “Once opened, the shelf life of jam significantly decreases. Storing opened jam in the fridge is the best way to extend its freshness. Typically, opened jam can last in the refrigerator for about one to three months.” 

It is best to store opened jam on the bottom shelf of your fridge as it has a more consistent temperature will help keep it fresh. 

Storing jam on the fridge door is fine but it is the warmest part of the fridge and the temperature fluctuations can increase the risk of spoilage. 

Once you have opened a jar of jam make sure you are always using a clean spoon that has no butter or toast crumbs on it as any contamination can cause mould growth. 

Mark said: “Never dip the same utensil back into the jam after spreading it on bread or another surface. This reduces the risk of cross-contamination.” 

Storing jam in the fridge will keep it fresh but unfortunately it can cause sugar to crystalise, and harden but if that happens it is very easy to fix. 

All you need to do is place a jar of jam in a bowl of warm water, then leave it for 10 minutes. This will help the jam dissolve so you have smooth and fresh jam ready to put on some toast. 

Unopened jam is fine to store at room temperature but do not place it in a cupboard that is next to a oven, air fryer or microwave as any heat will cause it to spoil even if sealed. 

Simply place a unopened jar of jam somewhere cool and dark in your kitchen, as sunlight will affect the flavour of jam and cause it to sour.