Why Mylar Bags Alone Aren’t Enough for Long-Term Storage

 

Mylar bags help block the most common threats to food freshness (light, moisture and air) but they do not remove any oxygen trapped inside the bag. Therefore, while Mylar will prevent further degradation from threats coming into contact with your food, without removing any oxygen already trapped in the bag your food will degrade in quality (through oxidation) even though the bag is completely sealed.

Oxidation continues, although at greatly reduced rates, long after your food is placed in a sealed Mylar bag. Over time, food stored in sealed bags will degrade, and in many instances you will have no warning until you eat the food and realize the decline in quality.

For food products that contain oils or fats (e.g., grain products, cereal mixes, etc.), the presence of oxygen in the sealed bag will cause the oil/fats to degrade (i.e., develop off-flavors) which will reduce the food’s nutritional value as well.

While the presence of oxygen can limit long-term storage, most people incorrectly believe that the act of sealing the bag preserves the food. Sealing just traps the food’s current state. If the food’s state (oxygen) is in the bag when sealed, then that unwanted state will remain in the bag.

This is why all long-term storage systems require an oxygen removal process, whether that be an oxygen absorber or a vacuum sealer; both processes address the internal environment of the bag and not just the external environment.

If you are attempting to store your food solely in Mylar bags, then you will be providing yourself with only a partial barrier against future degradation of your food. To gain a complete understanding of when oxygen absorbers become necessary for your Mylar bags, see Do You Have to Use Oxygen Absorbers in Mylar Bags?