The benefits of storing walnuts in bulk under Modified Atmosphere Packaging

Posted on 9 October 2023


Walnuts are one of the most popular nuts, enjoyed all over the world for their delicious taste and numerous health benefits. These nutrient-dense nuts are packed with protein, fiber, healthy fats, vitamins, and minerals that make them a powerhouse of nutrition. 


But making sure we can benefit from all that goodness, means walnuts have to be stored properly. They're at risk of not only losing their flavor, but also their nutritional value if not stored under ideal circumstances.


In this article we’ll dive into the storing of walnuts in bulk: why it’s challenging, and how our Modified Atmosphere Packaging solutions solve all your packaging problems and then some. 

The challenges of storing walnuts

Storing walnuts in bulk can be a challenging task. The quality of the walnuts can be affected by various factors, including light exposure, oxygen concentration, temperature, insect infestations, molds, autoxidation, and biological activity of the seeds.


One of the primary concerns for storing bulk walnuts is maintaining the light color of the kernels. Light-colored kernels command a higher price in the market, indicating a longer shelf-life. The darkening of the kernel skin is directly related to the oxygen concentration, with higher oxygen concentration resulting in faster darkening.


Another significant issue with long-term storage of walnuts is insect infestation, particularly the navel orange worm. Pre- and post-harvest infestation of insects like the walnut husk fly, codling moth, and Indian meal can cause damage to the walnuts.


Molds can also be a significant problem in bulk walnut storage, leading to the growth of mycelium that causes off-odors and mycotoxin production, such as aflatoxin. Autoxidation can cause degradation of fats, mostly unsaturated fats, leading to the formation of free fatty acids (FFA), rancid odors, and darkening of the kernels.


The biological activity of the seeds, like respiration, can cause elevated humidity levels and odors, which can also affect the quality of the walnuts. Moreover, walnuts' high lipid content makes them susceptible to absorbing odors from other commodities stored in the same vicinity.


Therefore, proper storage conditions, including low oxygen concentrations, temperatures below 10◦C, and appropriate pest control measures, are crucial for maintaining the quality of bulk walnuts during storage. Regular monitoring and testing for molds and mycotoxins are also necessary to ensure the safety of the walnuts for consumption.


All in all, there’s a lot to keep into account when storing walnuts. Luckily, there’s an all-in-one solution, with additional benefits.

Storing walnuts under Modified Atmosphere

Modified atmosphere storage (MAP) is a method of storing bulk walnuts that involves altering the atmosphere within the storage container to reduce oxygen levels and slow down the natural aging process of the nuts. MAP can be an effective way to tackle the challenges of storing walnuts in bulk, including issues related to light exposure, insect infestations, molds, and autoxidation.

Keeping the color just right

By lowering the oxygen concentration inside the storage container, MAP can slow down the darkening of the kernel skin, preserving the light color of the kernels and indicating a longer shelf-life. 

Preventing pests

Lower oxygen levels can also reduce the risk of insect infestations, such as the navel orange worm and other pests.

Slow down and prevent mold

Moreover, MAP can reduce the risk of mold growth, which can cause off-odors and mycotoxin production, such as aflatoxin. We’re able to maintain low oxygen levels for months on end. Read more about it here: Modified Atmosphere Packaging results for different food products

Quality preservation

Autoxidation can cause the degradation of unsaturated fats, leading to rancid odors and darkening of the kernels. MAP can help reduce the rate of autoxidation by limiting the amount of oxygen available, preserving the quality of the walnuts.

Reduced biological activity

Finally, MAP can reduce the biological activity of the seeds by slowing down respiration, which causes elevated humidity levels and odors. By maintaining a controlled atmosphere with low oxygen levels, MAP can keep the walnuts fresh and reduce the risk of spoilage.

Other benefits of Modified Atmosphere Packaging

Yes, there’s more. It’s not just your walnuts benefiting from MAP – your business does too, as does the environment:

  • Reducing food waste: MAP can help to reduce food waste by extending the shelf-life of products, thus reducing the need for frequent replenishment.
  • Increased product safety: By controlling the gas composition within the package, MAP can help to reduce the growth of pathogens and spoilage organisms, thus increasing product safety.
  • Improved product presentation: MAP can help to improve the appearance of the product by preventing discoloration, maintaining texture, and preserving flavor.
  • Cost savings: By extending the shelf-life of products, MAP can reduce the need for frequent replenishment and can also help to reduce product losses due to spoilage.
  • No need for chemicals: MAP allows for the preservation of food products without the need for chemical preservatives. Consumers love it, and the planet does too. Read more: Pest control methods: Fumigation vs Modified atmosphere 
  • More control over the supply chain: MAP allows for more control over the supply chain as products can be packaged and sealed at the point of production, reducing the risk of contamination during transit or storage. This can also help to reduce the risk of product recalls, as products can be traced back to their source more easily, and any issues can be identified and addressed more quickly. Read more: Safe and fast quality control for Modified Atmosphere Packaging 


Want to find out what Modified Atmosphere Packaging can do for your product? Reach out to our team for tailored advice and fact sheets relevant to your business.


Want to work towards sustainable supply chain management?

At Masterpack, we are continuously working towards better ways to pack and protect products. We proudly present our newest solution: Modified Atmosphere for FIBC’s. Download our latest whitepapers:

Testing and improving your packaging (1,6MB)
Modified Atmosphere in FIBC's (6,4MB)
Pest prevention and control in bulk packaging (2,8MB)
The Modified Atmosphere Packaging Process Whitepaper

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