My daughter told me she and her friends made strawberry jam that they processed in a dishwasher rather than in a boiling water bath. This sounds dangerous to me, and I wanted to know your opinion.
OSU Extension does not recommend using a dishwasher for processing jam. The heat penetration will be uneven and insufficient. These jars need to be brought up to boiling water temperature, 212º F at sea level. Most dishwashers don't get above 165º F. Jars processed in dry heat can also explode and cause the glass to break, which is a safety hazard.
For jams, a boiling water bath canner should be used. Jams need to be fully submerged in water during processing to expel the oxygen that could help produce mold if left unprocessed.
Preventing spoilage in jams
To prevent spoilage from mold in the jam that your daughter made, she can store the jam in the refrigerator for use in the near future or freeze it.
If she chooses to freeze the jam, be sure to open it and increase the headspace by about 1/2" before it goes in the freezer. This way, the jar won't break from the expanding jam. The jar lids should be a little loose so air can get out while it is freezing. Tighten the jar lids after the jam has frozen.
Jams can be made completely uncooked and frozen in the freezer rather than canned. Check out the following resources to learn more:
Water bath canning
Home canners living on a budget can make their own water bath canners from:
- An existing tall cooking pot. It needs to be able to hold water that will measure 1 to 2 inches above the tallest jar while the water is boiling.
- A metal tray that elevates the jars off of the bottom of the pot for good water circulation and heat penetration. The metal tray could be from the bottom of a pressure canner (these are sold separately at stores that sell canning supplies or on-line), possibly a round cake cooling rack, the rack from a pressure cooker, or make a trivet of canning jar rings held together with twist-y ties.
- A tight-fitting lid
There is no substitute equipment for a pressure canner.
The following resources have safe recipes and preservation methods for making jams: