Dried Foods and Spoilage: How to Tell if Your Dehydrated Foods Have Spoiled and How to Prevent It

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Dried Foods and Spoilage: How to Determine if Your Dried Foods have Spoiled, and How to Prevent Spoilage of Dehydrated Fruits and Vegetables

It can be tough to accurately determine whether any food has gone bad without a lab test, since many pathogens (botulism, as an example) leave no visible signs, and are colorless, odorless, tasteless, etc.. Generally, we rely on following the approved preparation and canning/freezing/drying process rigorously to ensure safety is built in.

But dried foods can be even more difficult. Mostly it depends upon how carefully the foods were prepared and dried (cleanliness and attaining the optimal moisture content for the produce), and then how they were stored. Dried foods kept in the freezer can last years.

Determining if dehydrated foods have spoiled:

Assuming you don't have access to a food science laboratory:

  1. Visible signs - - obvious mold, liquids oozing, unexpected changes in color
  2. Odor - bad smells
  3. Texture - chewy, rather than crisp, or different textures from what is normal for a particular food.
  4. Taste - obviously, if you suspect a food has spoiled, tasting it is a dumb idea. BUT, if the food otherwise seems fine and upon tasting it, it does not taste as it should, that is a reason to discard it.

General Tips to prevent spoilage:

Dried foods are susceptible to insect contamination and moisture reabsorption and must be properly packaged and stored immediately. First, cool completely. Warm food causes sweating which could provide enough moisture for mold to grow. Pack foods into clean, dry insect-proof containers as tightly as possible without crushing.

Conatiners: Store dried foods in clean, dry home canning jars, plastic freezer containers with tight-fitting lids or in plastic freezer bags. Vacuum packaging is also a good option. Pack foods in amounts that can be used all at once. Each time a package is re-opened, the food is exposed to air and moisture that can lower the quality of the food and result in spoilage.

Quantities: Pack food in amounts that will be used in a recipe. Every time a package is re-opened, the food is exposed to air and moisture that lower the quality of the food.

Sulphuring: Fruit that has been sulfured should not touch metal. Place the fruit in a plastic bag before storing it in a metal can. Sulfur fumes will react with the metal and cause color changes in the fruit.

Light and Heat: Dried foods should be stored in cool, dry, dark areas.

Time in storage: Recommended storage times for dried foods range from 4 months to 1 year. Because food quality is affected by heat, the storage temperature helps determine the length of storage; the higher the temperature, the shorter the storage time. Most dried fruits can be stored for 1 year at 60ºF, 6 months at 80ºF. Vegetables have about half the shelf-life of fruits. Dried foods kept in a good deep freezer can last almostg indefinitely.

Check for moisture: Foods that are packaged seemingly "bone dry" can spoil if moisture is reabsorbed during storage. Check dried foods frequently during storage to see if they are still dry. Glass containers are excellent for storage because any moisture that collects on the inside can be seen easily. Foods affected by moisture, but not spoiled, should be used immediately or redried and repackaged. Moldy foods should be discarded.


Tips during preparation:

Conditioning Fruits

The moisture content of home dried fruit should be about 20 percent. When the fruit is taken from the dehydrator, the remaining moisture may not be distributed equally among the pieces because of their size or their location in the dehydrator. Conditioning is the process used to equalize the moisture. It reduces the risk of mold growth.

To condition the fruit, take the dried fruit that has cooled and pack it loosely in plastic or glass jars. Seal the containers and let them stand for 7 to 10 days. The excess moisture in some pieces will be absorbed by the drier pieces. Shake the jars daily to separate the pieces and check the moisture condensation. If condensation develops in the jar, return the fruit to the dehydrator for more drying. After conditioning, package and store the fruit as described above.

Determining Dryness of Vegetables

Vegetables should be dried until they are brittle or "crisp." Some vegetables actually shatter if hit with a hammer. At this stage, they should contain about 10 percent moisture. Because they are so dry, they do not need conditioning like fruits.


Dried food is sometimes contaminated by insects or molds, which can cause spoilage. Sulfuring fruit usually prevents this type of contamination. After meat and vegetables have been dried, they can be pasteurized to make them safe. It is especially important to pasteurize food dried outdoors, where it was probably contaminated.

To pasteurize, heat the oven to 175 degrees F. (80 C.). Set the pieces of dried food in a single layer on a tray or cookie sheet. Heat in the oven with the door closed for 15 minutes. Remove from the oven and allow the food to cool before packaging. Alternatively, the dried food can be pasteurized by freezing it for 1 to 2 weeks and then storing it.


For detailed steps on drying foods and Food Drying Principles, see this page.

Here's the food dehydrator I use!:


How to dry various foods, fruits and vegetables


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