What causes foggy buildup inside sealed pantry jars?

Question

Noticed a foggy film inside your sealed jars? Learn what can cause this to happen and if it's a sign of a problem with your stored food.

Answer 1

Foggy buildup inside sealed pantry jars is usually caused by moisture from the food item itself or from condensation during temperature fluctuations. This moisture then evaporates and re-condenses on the cooler surfaces of the jar.

Detailed Explanation:

The primary culprit behind foggy jars is moisture. Here's a breakdown of how it happens:

1. Moisture in Food: Many dry goods, even those that appear dry, contain some level of moisture. When you seal the jar, this moisture can evaporate.
2. Temperature Fluctuations: Changes in temperature, especially in pantries that aren't climate-controlled, cause condensation. Warm air holds more moisture than cold air. When warm, moist air inside the jar cools, the moisture condenses on the inside surface of the glass.
3. Inadequate Drying: If the jar wasn't completely dry before you filled it, residual moisture will contribute to the fog.
4. Respiration of Food: Some foods, like grains and seeds, continue to respire (breathe) even after being dried. This process releases moisture and carbon dioxide.

Over time, this cycle of evaporation and condensation leads to the foggy appearance inside the jar. It's generally harmless, but excessive moisture can lead to mold growth or spoilage, especially in certain foods.

Pro Tip:

Before sealing your pantry jars, consider adding a food-safe desiccant packet (like those found in vitamin bottles, but new and unused) to absorb excess moisture. This can significantly reduce fogging and extend the shelf life of your stored goods.