How to: Sterilise and Seal Jars for Preserves and Jams

Using properly sterilised jars is essential when preserving.

This is what Mum does to sterilise preserving jars:

Clean the jars with hot soapy water and then rinse well. Pour boiling water into the jar for an extra hot rinse, then dry. The heat will also help dry the jar quicker.

Place the jar onto oven trays or racks (making sure they are stable) and heat at 150 degrees Celsius for at least 20 minutes. (I have come across other versions that are 100-120 degrees Celsius for 30 minutes, or 170 degrees for 10 minutes).

For the lids: sterilise by boiling lids in water for 10 minutes.

Mum used metal screw bands that have a hole in the middle which allows a flat metal lid to fit inside. When the jar is cooled the screw bands are removed leaving the flat metal lid covering the preserves (for an example of the flat metal lid see photo in the blog Feijoas Poached in Ginger Syrup). The screw bands can be reused, but the flat metal lids should only be used once as this is touching the preserved foods inside the jar.

Filling the jars:

Wide-necked jars are easier to fill. Fill the jars with the preserves as soon as the jars come out of the oven. Remove the jars only when you need them (one at a time) so they stay hot. Never put cool preserves into hot jars, or put hot food into cold or cool jars, as they can shatter. When filling the jar, tap it gently on the bench surface to make sure any air pockets surrounding the contents in the jar are removed. Top up the level in the jars to the brim (or overflowing) as this makes sure no air is left in the jar as the air will make the preserves deteriorate quickly. Seal immediately. The preserves are sealed when the lid has a slight concave, which is from the suction inside the jar as the preserves and jar cool. If the last jar doesn’t have enough contents to fill it completely, use it first as it will not keep.

For jams and jellies, a cellophane covering tied in place with a rubber-band is sufficient to seal the contents (see my blog on Mum’s Crabapple Jelly for an example).

New Zealand company Old Mill Road stock a range of lovely jars. I have their spice jars and the old-style chunky, square glass jars with metal screw-top lids in a range of sizes. They stock old-style retro jars as well as modern styles of spice jars and pantry jars. Everything is practical as well as stylish. See the website www.oldmillroad.co