Walnut Processing: From Hulling To Packing

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The California nut industry just keeps growing and growing! Not only are more orchards being converted into nut orchards, but there is also a lot of money being put into research to improve the nut industries.  In regards to walnuts, California supplies 100% of the walnuts to the U.S. market and 99% or more of walnuts to the global marketplace, with walnuts being the 2nd highest exported nut (behind almonds). In addition to the growing process, there is an additional walnut processing step required to remove the shell to provide a ready-to-eat product for the consumer.

Below, you will get to see the work that it takes to bring those walnuts to you! All of the footage was gathered from Andersen and Sons Shelling, Inc. in Vina, California.

Table of Contents

Walnut Processing

Walnut processing consists of hulling, drying, storage (like insane storage rooms full of walnuts!), shelling, packing and pasteurization. The video below displays a step-by-step of what takes place during walnut processing.

The reasons for each step are as follows.

Walnut Hulling

Walnut hulling is the process of removing the hull, which is a dry outer covering located outside of the shell as the walnuts grow on the tree. 

As you can see in the picture below, the hull is the green portion located outside of the walnut shells that we are used to seeing.

Walnut Hull

Hulling is performed after harvest and before the walnuts arrive at the processor. As you can see below, the nuts on the left have not been hulled, while the nuts on the right have just arrived at the processor and have been hulled.

Walnut Processing - Walnuts Prior to Hulling
Walnut Processing - Walnuts After Hulling

Walnut Drying

After the walnuts are hulled, they are sent to a drying room where the walnuts are dried until they reach the desired moisture content.

Walnut Drying

Walnut Storage

When walnuts arrive at the processor, they go into storage. Similar to other dried fruits and nuts, the walnut harvest season only lasts a few months, and the walnut supply for the rest of the year is fulfilled from storage. As you can see below on the left, walnuts are commonly stored in bulk rooms that are basically a large pile of walnuts throughout a warehouse, as well as in stacked bins in a storage room shown on the right.

Walnut Processing - Walnut Bulk Room Storage
Walnut Processing - Walnut Bulk Bin Storage

Walnut Shelling

Walnuts go through a shelling process, where the shells are cracked and removed.  Once the shell is removed, the kernels are sorted by the size of the kernels: large, half and small pieces.

Walnut Kernels

After being shelled, the kernels are ran through another machine containing three lasers that sort by kernel color (the lighter colored kernels are the most lucrative) and remove any leftover shell particles.

Walnut Laser Sorter

Walnut Packing

Walnuts are packed according to customer specifications. The three methods in which walnuts are packed are: in-shell packed, bulk packed or retail packed. The retail packed walnuts is the only option where the packaging is for the final consumer.

Walnuts are packed based on when an order arrives, which explains the large bulk storage rooms.

Walnut Pasteurization

Pasteurization is a method used to remove microorganisms by heating up the nuts to a very high temperature for a short amount of time, and then cooling them down. This method is commonly used with nuts, and is currently an optional practice for walnuts.

(You can click here to learn more about the specific pasteurization machine used at Andersen and Sons Shelling, Inc.) 

Walnut Pasteurization Machine

Frequently Asked Questions

What are the most popular walnut varieties grown in California?

According to the 2019 USDA Reporting, Chandler, Tulare and Hartley are the most common varieties.

Where are walnuts grown in California?

The three main growing regions in California are San Joaquin County, Butte County and Tulare County.

The facility shown above is located in Vina, California, which is just outside of Butte County.

Are all walnuts pasteurized?

No, pasteurization is currently an optional practice for walnuts.

Can I order walnuts online?

Yes, you can support this company’s shop that sells multiple different types of nuts online here

Featured Company Information

I would like to thank Andersen and Sons Shelling, Inc. for the tour and for allowing the gathered content to be shared. Walnuts are the main focus for Anderson and Sons Shelling, but they have also started getting into other nuts recently as well, such as pecans. 

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This Post Has 4 Comments

  1. MLBotma

    I have recently been told that conventionally grown walnuts are sprayed with harmful pesticides (glyphosate) more than most any other nut. They also said that they are even sprayed AFTER the walnut has been shelled. Can you please confirm/deny this for me? Thank you for your time!

    1. Ryan Fillmore

      Hi ML, great questions.
      Conventionally grown walnuts, especially those using drip irrigation, often have the tree row sprayed with herbicides (contact and pre-emergent) during the growing season to prevent weeds from growing. This keeps the berm clear for irrigation and harvest. Some farmers will spray the entire orchard floor with herbicide a few weeks prior to harvest to make the harvest process easier. The herbicides used conventionally often contain glyphosate. Since nuts are shaken from the tree and picked up off the ground in their shells, there is always a possibility of increased herbicide levels both from the ground contact as well as through the tree as a result. How much of an increase vary widely and is often hard to detect without a laboratory analysis.

      The good news is I am not aware of any processing facility in California that sprays walnuts with herbicides after they have been shelled. Many plants use a form of steam pasteurization or chemical fumigation, though. Virtually all conventionally grown walnuts are fumigated in their shells with PPO for insect control. Occasionally the kernels will also be fumigated after cracking, but steam pasteurization is becoming much more common.

      Organic walnuts cannot be fumigated and remain organic, so most are frozen inshell before cracking. Most organic walnut kernels are also steam pasteurized after cracking and sorting.

      Both Anderson & Sons and our company, Fillmore Farms, handle Organic walnuts. The National Organic Program does not allow glyphosate or any other synthetic herbicide during the growing or processing of organic walnuts. We also use a freeze process rather than a chemical fumigation to control insect pressure in the inshell nuts.
      Regards.

  2. Jeann

    Same here. Would love an answer.

  3. Cindy

    What is almond hulling used fo

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