No — botulism is not a realistic concern for typical refrigerator jam.
Clostridium botulinum can only produce toxin under a specific set of
conditions:
- Low acidity (pH above ~4.6)
- Anaerobic (low-oxygen) environment
- Available moisture
- Temperatures that allow bacterial growth
Fruit jams do not meet those conditions.
Most fruits used for jam are naturally acidic, typically around pH
2.8–3.8. That is well below the ~4.6 pH threshold required for
C. botulinum toxin production. Many recipes also add lemon juice,
which further lowers the pH.
In addition, traditional jams contain a high concentration of sugar.
This reduces water activity, which makes the environment even less
favorable for bacterial growth. Storing the jam in the refrigerator
adds another barrier by slowing microbial activity.
Because of these multiple hurdles — high acidity, high sugar content,
and refrigeration — botulism is extremely unlikely in fruit-based
refrigerator jams.
The more realistic issue with refrigerator jam is simple spoilage,
such as mold or yeast growth over time. Using clean utensils, keeping
the jar refrigerated, and consuming it within a few weeks are the
usual precautions.
Botulism concerns in home preservation are primarily associated with
improperly canned low-acid foods stored at room temperature (for
example vegetables, meats, or garlic in oil), not acidic fruit
preserves kept in the refrigerator.
