Sterilising jam jars - all you need to know

Sterilising jam jars - all you need to know

Posted by Lizzie Quarmby on 20th Jul 2018

Before you begin the delicious process of preserving, there is one very important step you must take, which is sterilising jam jars and other accessories. It's far less fun than cooking but is essential.

Sterilising glass jars - why and how!

The process of sterilisation ensures that any bacteria, fungi, yeasts and any other unwanted organisms are removed from jam jars and lids so that your preserves will not be contaminated by them. If these nasties are allowed to remain in the jars and come into contact with jams and preserves, they can spoil your food and, even worse, could make you ill when you eat it.

So for the sake of freshness and your health, make sure you always sterilise not only the jam jars themselves but also any lids or seals that go with them.

Before you begin, check your glass jars and lids carefully and discard any which are damaged. Cracks, chips and other damage can hoard bacteria and can be dangerous to handle. Wares of Knutsford can supply supply spare lids to replace any which are not good enough to re-use. Before you sterilise, wash jars thoroughly in hot, soapy water and rinse well.

There are a couple of easy ways how to sterilise jars, but whichever you use, try to do it at the same time you are preparing your preserves, as the jars should still be warm from the preserving process to avoid cracking the glass when you fill them with hot jam and to help create an efficient seal.

How to sterilise jam jars

Firstly and most simply, you can sterilise your jars in the dishwasher, running them through a hot cycle. If you are re-using lids, remove any rubbers seals before washing and sterilising.

However, many people prefer sterilising jam jars in a water bath. You will need a pan large enough to hold your jars and lids, then cover them with plenty of water. Bring the pan to a rapid boil and hold it for at least 10 minutes. Don't ever put your jars into already boiling water as the glass could crack, and make sure you use oven gloves or a set of special tongs for jam jars to handle the hot jars and lids.

Placing the jars in an oven on a low temperature used to be a popular method for sterilising but has fallen out of favour due to a risk of bacterial contamination from food stuck onto the oven surfaces, so unless your oven is absolutely spotless you are probably better off using one of the wet methods above.