Why does cooked jam ferment?

Cooked jam ferments due to the presence of yeasts and molds that can survive the cooking process. Yeasts and molds are naturally occurring microorganisms that are present in the air, soil, and on fruits. When jam is cooked, the high sugar content creates a favorable environment for these microorganisms to grow and multiply.

Yeasts convert the sugars in jam into alcohol and carbon dioxide, which can cause the jam to become fizzy or bubbly. Molds, on the other hand, can cause the jam to become fuzzy or slimy, and can also produce toxins that can make the jam unsafe to eat.

To prevent cooked jam from fermenting, it is important to follow proper canning and preservation techniques. This may include:

- Using sterilized jars and lids

- Processing the jam at a sufficiently high temperature for an adequate amount of time

- Adding a preservative, such as sugar, salt, or lemon juice

- Storing the jam in a cool, dry place