Walnut Storage & Handling
The Health Benefits of Walnuts
Today’s health-conscious consumers look for foods that are nutritious and versatile. Numerous research studies have shown that the polyunsaturated fats in walnuts help lower cholesterol and reduce the risk of heart disease. Walnuts also are an important source of fiber, as well as essential minerals and vitamins – especially the antioxidant vitamin E. Plus, walnuts contain amino acids, the building blocks of protein, which are necessary for normal growth and development. According to the California Walnut Board, Walnuts:
- Are Heart Helping: Walnuts help maintain healthy cholesterol levels and decrease blood pressure, two of the major risk factors for heart disease.
- Help You Feel Satisfied: An ounce of walnuts offers 4 grams of protein and 2 grams of fiber. Most Americans don’t get enough dietary fiber, which promotes healthy bowel function and helps you feel full–a key component in maintaining a healthy weight.
- Contain Good Fats: A growing body of scientific evidence is beginning to uncover a variety of benefits that ALA/omega-3s may provide to our bodies. While most nuts contain monounsaturated fats, only walnuts are comprised primarily of polyunsaturated fat (13 grams out of 18 grams total fat).
Find out more, including other sources of helpful information at walnuts.org.
Storage and Handling: Walnuts
Refrigerated storage of walnuts is critical to prevent the development of rancidity and/or infestations of insects. The ideal storage conditions are below 35° F and 70% relative humidity. Long-term storage should be near 0° F in order to maximize freshness and shelf life.
| Refrigerator or Freezer | Shelled | In-Shell |
|---|---|---|
| Unopened Package | 24 months | 24 months |
| Opened Package | 12 months | 18 months |
- Frozen walnuts should be tempered by gradually raising the temperature in a humidity and temperature controlled environment in order to minimize condensation and the resulting risk of mold.
- High-velocity air movement around the walnuts speeds up the tempering process and helps minimize the possibility of condensation problems.
Storage Atmosphere
Walnuts readily absorb moisture, gases or odors from the atmosphere, which may change the flavor, color, texture or stability. These may be odors of the building, volatile gases, or respiration products from stored commodities. For this reason, walnuts should be stored in separate rooms, away from other products that may be the source of odors or flavors.
Ammonia Damage
Traces of ammonia, not detectable by order, in the storage room will blacken the seed coat of walnuts within a few weeks and of unshelled walnuts within two months. While the walnuts are permanently damaged in color, there is no noticeable difference in the flavor or taste. Blackening increases with the ammonia concentration, temperature, time and amount of exposure. To prevent ammonia damage, walnuts should always be stored in facilities that utilize a refrigerant other than ammonia.
Storage Insects
Insects are a major problem in walnuts and nut products stored at temperatures above 45° F, especially if they are shelled. The most common insects that infest nuts are Confused Flour Beetle, Indian Meal Moth, and Saw-Toothed Grain Beetle. These insects all eventually infest tree nut meats that are out of storage for more than two weeks during the warm weather months, unless they are sealed in an airtight container.