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Why Does Grain Go Bad?

Whether you’re growing and harvesting your own crops or buying them in bulk, it’s disappointing to discover that your grains have spoiled. While many grains and flours have long shelf lives, they can quickly deteriorate if stored improperly. You may even notice visible discoloration, mold or stale grains. 

Like with refrigerated foods and perishables, knowing how to store your grains correctly is essential. Many factors can impact grains’ nutritional quality and flavor, including poor grain bin management, extreme temperatures, moisture and pest infestations. Use this guide to learn more about the shelf life of certain grains and how to keep them fresh! 

How Long Can Grains Be Stored?

A grain’s shelf life largely depends on the type and how it’s stored — just as with any food or crop. Every type of grain has varying fat content which influences its specific shelf life. However, all grains typically stay fresh longer when stored in a cool, dry, dark location. Here are some rules of thumb when storing bulk grains:

  • Whole intact grains: Intact grains, like brown rice and wheat berries, will generally keep fresh for up to six months if stored in airtight containers.
  • Cooked grains: Prepared grains should be stored in the fridge and eaten within several days, depending on how they are mixed. 
  • Frozen grains and flours: Whole intact grains can last up to about one year in the freezer, while most whole-grain flours and meals can last between two to six months frozen. Cooked grains can keep fresh in the freezer for about six months. 
  • Whole grain flours: These will keep fresh for about one to three months, but they tend to spoil faster than whole intact grains.
  • Hard grains: Certain grains — including wheat, spelt, corn, flax, buckwheat, millet and kamut — have hard outer shells that can help prolong their shelf life.

Common Causes of Grain Spoilage

Grain damage and spoilage can occur for many reasons, affecting the quality and flavor. Here are the most common reasons why your grain might be going bad. 

1. Temperature

Insufficient temperature control can cause your grains to spoil. Certain types of grain, like wheat and quinoa, are more sensitive to temperature fluctuations. Hard grains like rice are less likely to be affected by slight changes in temperature, but extreme fluctuations can sometimes result in condensation, which causes your grain to rot. 

Maintaining consistent temperatures can significantly improve your grain’s longevity. As a rule of thumb, all types of grain should be stored in a cool, dry area. Around 70 degrees Fahrenheit is ideal to prevent mold growth. 

Always check the expiration date on your bags of grain or document when it was harvested. If there’s a noticeable change in your grains, such as color, odor or texture, it’s safe to assume they’ve spoiled. Always err on the side of caution and get fresh grains. 

2. Humidity and Moisture

As with high temperatures, your grain will spoil if there’s too much moisture in the air. It’s critical to keep even humidity levels throughout the grains to prevent damage. For example, soft grains like quinoa can sprout relatively quickly with even the smallest amount of moisture, so it’s important to keep an eye on moisture levels. The longer your grains are in storage, the lower moisture content they should have.

Likewise, if your grains are not properly dried before they go into bags or containers for long-term storage, they’ll spoil much faster. Ideal humidity levels can vary depending on location, season, temperature and rainfall. Be sure to reference a grain moisture chart to determine the proper humidity and temperature for storing your specific grain type. You can also check out the Whole Grains Council Resources for more details on storing whole grains.

3. Pests

Improper storage can also make it easier for bugs, rodents and other pests to get into your grains. A lack of airtight containers and temperature control can trap heat and moisture, creating the perfect breeding ground for bugs. Here are the most common pests and insects you’ll find in grain storage:

  • Granary weevil 
  • Rice weevil
  • Maize weevil
  • Lesser grain borer
  • Angoumois grain moth
  • Cadelle beetle
  • Confused flour beetle
  • Flat grain beetle
  • Red flour beetle
  • Sawtoothed grain beetle
  • Indian meal moth

The best way to prevent pest infestation in grain storage is to perform routine inspections of your grain and maintain your storage location. If you suspect insects or pests have penetrated your grains, look for these common signs of an infestation:

  • Small holes in the packaging
  • A sweet, musty odor
  • Damaged or discolored grains
  • Holes in kernels and grains
  • Powdery substance on the grains
  • Insect webbing
  • Bug droppings
  • Increased grain temperature

Proper Grain Storage Techniques

The most effective way to keep your grains fresh and high-quality is to implement preventative methods. Here are some best practices for storing bulk grains. 

1. Use High-Quality Storage Containers

Your grain is usually only as good as the containers you store it in. There are many high-quality storage products and equipment on the market, such as:

  • Cushion boxes.
  • Slide gates.
  • Valves.
  • Bulk grain bags.
  • Mylar bags.
  • Food-grade buckets.

Using high-quality storage containers can help protect your grains from potential contaminants like mold and bugs and preserve their nutritional value. You can also extend the shelf life of your bulk grains by keeping them in airtight, pest-resistant containers.

2. Level Your Grains

Temperature regulation is a top priority for keeping stored grains fresh. Leveling the grain surface can help with temperature control. A common leveling technique called “coring” involves removing the center of the grain column to dispose of accumulated fines. It’s important to level the grain when storing it in bulk quantities to provide more uniform airflow and make it less likely to change temperature. 

3. Avoid Direct Sunlight

Artificial and direct sunlight can make it challenging to maintain stable grain storage temperatures. Generally, darker places tend to remain at consistent temperatures as opposed to environments that receive natural sunlight. Light can also contribute to mold growth or cause your grain to become brittle. It’s important to store your grains in a light-proof container or a dark space to regulate temperature.

4. Dry Grains Properly

As noted above, moisture can be problematic for your grain. Be sure to dry your grains properly before putting them in long-term storage. This step is particularly crucial if you grow the grains yourself.

5. Check for Quality

If you plant, harvest and grow your own crops, you likely take measures for quality assurance. However, it still helps to perform an extra quality check before you put them in storage. Sort through your crops and look for damaged, cracked, discolored or odorous grains. Periodically check your grains in long-term storage and look for signs of spoilage, pests or mold.

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