How to master dry pasteurisation: A complete oven guide

My neighbour can pasteurise several jars at once. When I asked her where she buys such large pots to fit everything in, she laughed. It turns out she has long been using another, equally effective method.

Pasteurisation is the process in which food undergoes heat treatment. This allows food products to be stored for a longer period by significantly reducing the activity of microorganisms such as bacteria, yeasts, and moulds. At home, jars are typically pasteurised using a pot of boiling water, but recently, an alternative, even simpler method has been gaining popularity.

Dry pasteurisation is a method of preservation using an oven. As the name suggests, this type of pasteurisation does not require water; the heating elements in the appliance provide the temperature. But how do you go about dry pasteurisation to ensure the preserves are properly preserved?

A few details need to be considered to prepare well for dry pasteurisation. Firstly, only twist-off jars, the classic type with a screw cap, are suitable for oven pasteurisation. Various containers with flexible rubber or rubber seals may not be suitable for such high temperatures. Secondly, jars must be undamaged, not even scratched. This is obvious to anyone who makes preserves at home. However, before dry pasteurisation in the oven, special attention should be paid to this. It is also worth remembering not to fill the jars with preserves to the very top. About an inch of free space should be left.

1. Place prepared and capped jars (you don't need to tighten the jars too much) with preserves on a baking tray lined with baking paper or a tea towel. Arrange the jars so they do not touch each other or the oven walls. Importantly, place the jars with the caps facing upwards.
2. The next important thing is the pasteurisation temperature. When dry pasteurising in an oven, the same method applies to classic pasteurisation in a pot. Thus, cold preserves are pasteurised from a cold oven, and hot preserves from a preheated oven.
3. If you put preserves into a hot oven, preheat the appliance to 248°F (no fan). Conversely, if you are pasteurising cold preserves, place the tray in the oven and then set the oven to the same temperature.
4. How to time the pasteurisation? For a preheated oven, it's simple: about half an hour from placing the tray with jars inside. However, if you are pasteurising from a cold oven, count 30 minutes from when the oven heats up. Most modern ovens have a light that goes out when the appliance reaches the set temperature. The most modern ones inform you on the display.
5. After the indicated time, leave the jars in the oven for 30 minutes with the door ajar. When they cool, tighten the lids and store the jars upside down for 24 hours. After that time, store the preserves in a dark and cool place.