There are a few factors that determine how long food will last after it is opened. They include the following:
- The quality of the food at the time it is opened
- The degree to which food is exposed to oxygen and moisture
- The degree to which food is exposed to heat and light
The quality of the food at the time it is opened:
The older food storage gets and the more it is subjected to fluctuating temperatures, meaning below freezing and above 80 degrees, the more deterioration has probably occurred to the food inside the container.
The degree to which food is exposed to oxygen and moisture:
The moment the container is opened, the food is exposed to air. Air contains both oxygen and moisture. Many organisms require oxygen to survive. The higher the humidity (moisture content) of the air, the faster the product quality (nutrition and taste) deteriorates.
The degree to which food is exposed to heat and light: Temperature greatly affects the speed at which food deteriorates. The higher the temperature is, the faster the quality (nutrition and taste) deteriorates and the shorter the time that food stays edible and safe. Since many organisms require light to grow, exposure to light also causes deterioration.
Recommendation: Once you have opened your food storage, you can prolong its shelf life by eliminating the adverse affects listed above. Store your food in the coolest, darkest and most airtight environment possible. Consider the following options to extend the life of food, once the container has been opened.
- Pour what has not been used into a zip top freezer bag and seal the bag. Place the bagged food back into the can and replace the lid (to eliminate light).
- Pour the remaining food into containers, which offer an airtight seal.
- Commercially available sealers can create an airtight environment. Put the food back into the can with the plastic lid secured.
- Generally speaking, refrigeration or frozen storage can extend the life of food. If you do not have much refrigeration or frozen storage space, use a pantry, cupboard, etc.
As a general rule, food stored in a #10 can or a bucket, depending on the above factors, may stay good up to one year after opening. Use your best judgment in deciding which food items to use. One way to determine if food is still of acceptable quality is to verify that it smells normal. Another way is to taste it or cook with it. If the quality of the finished product is satisfactory, continue to use it. Although food will lose nutritive value over time, old food retains some caloric and mineral value. It may have some life sustaining ability remaining. The information above are general guidelines intended to help make an educated decision. Each situation is unique due to many contributing factors.