Walnut Guide

Walnuts are true tree nuts, composed of a seed surrounded by dry fruit and encased in a hard shell with the scientific name Juglans regia from any tree of the genus Juglans (family Juglandaceae). Walnuts are another seed masquerading as a nut. Their shells mature and harden inside of a fibrous, green husk, but it's common to extract the walnut prematurely for the English delicacy pickled walnuts.

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The most popular variety of walnut is Persian walnut. This is so named to indicate its place of origin, and has grown in many parts of the world. This variety is commonly called "English" walnut, but it is also known by other names such as "Carpathian" walnut, and "California" walnut. Other famous varieties include Serr, Howard, Chandler, Vina, Sunland, Hartley, Eureka and Tulare.

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There are some variations in how walnuts are harvested depending on the country of origin. Harvesting is done either manually or mechanically with a machine (a small vehicle with an arm to grip the trunk) that shakes the tree causing the nut pods to fall to the ground. If the nuts remain on the ground for a prolonged time, they can become susceptible to infestation or rot. During this time, it is important to remove mummy nuts (unharvested nuts) and damaged nuts to lessen the likelihood of damage from the navel orange worm.

Once the walnuts have dropped to the ground, the walnuts are swept into rows in between the trees and collected from the orchard floor quite quickly in order to reduce the chances of pest damage. They are then transported to the processing plant. Upon reception at the plant, the pods are given a water bath before continuing on to be processed. This is an initial cleaning stage to remove any branches, leaves, or extra dirt that may have been collected with the walnut pods.

The processing steps of walnut are basically divided as follows:

• Fresh, for direct consumption.
• Processed in oil, flour, etc.
• As an ingredient for the food manufacturing industry.

The nuts are processed after harvesting and reception. This starts with a dehulling to reveal the in-shell walnut. This can be done mechanically or by hand. Once this is complete the nuts are left to dry, most commonly done in large containers that are air-dried, until the moisture reaches a level of about 5-8%. As some factories use wooden drying racks with metal nails, this can be a point of foreign body contamination and should be considered a point of extra care. This is an important processing step as it helps to maintain the quality of the nut and avoid deterioration during storage time. Walnuts can be processed both in-shell or shelled. If the nut is going to remain in the shell, the shells are cleaned and prepared for packaging. These nuts are commonly used for oils. Otherwise, the nuts continue on through further processing. After the walnuts have been dried they are shelled. This is typically done mechanically. Shelling mechanically can increase the risk of damage to the kernels, but this is very slight. Shelling can also be done by hand with a hammer/mallet which can be better for the kernel but requires more time and manpower.

The harvesting season depends upon the variety and region walnuts are grown in. Walnut tree harvesting starts from early September to early November. At this point, the kernels are light in color and the membrane between the halves has turned brown. The harvest begins when the nuts have matured and a high percentage of nuts on the tree have split hulls, usually, a small number of nuts have already started to naturally fall to the ground. In that case, collect nuts as soon as possible to avoid mold. Hulls soften naturally over time, allowing easy access to the nut.

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Referring to UNECE, the quality factors of walnuts are based on oil content, size, color, and nut defects. The walnuts are sorted throughout processing into three classes (extra, I, II). This is decided by size and color (extra light to amber). Examples of defects that are looked for and sorted out during processing are mold/rot, shell fragments, and insect damage. Defects that are allowed some tolerance are dark kernels, mold/rot, and scuffs.

The purpose of the standard is to define the quality requirements for walnut kernels at the export control stage, after preparation and packaging, further as follows:

Walnut Minimum Requirements (referring to UNECE)

a) In all classes, subject to the special provisions for each class and the tolerances allowed, walnut kernels must be:

• Sufficiently dry to ensure keeping quality;
• Sound; produce affected by rotting or deterioration such as to make it unfit for consumption is excluded;
• Firm;
• Sufficiently developed; shriveled kernels are to be excluded;
• Clean, practically free from any visible foreign matter and from shell;
• Free from insects or mites whatever their stage of development;
• Free from damage caused by pests ;
• Free of any rancidity or oily appearance;
• Free from mold;
• Free of abnormal external moisture; and
• Free of foreign smell and/or taste.

The condition of the walnut kernels must be such as to enable them:

- To withstand transport and handling; and

- To arrive in satisfactory condition at the place of destination.

b) Moisture content

The walnut kernels shall have a moisture content of not greater than 5 percent.

Walnut UECE Classification

a) "Extra" Class

Walnut kernels in this class must be of superior quality, uniformly light-colored with practically no dark straw and/or lemon-yellow color and with no dark brown. They must be characteristic of the variety and/or commercial type. They must be practically free from defects with the exception of very slight superficial defects provided that these do not affect the general appearance of the produce, the quality, the keeping quality, or its presentation in the package.

Scuffing is allowed on:

- Quarters and all pieces; and

- Halves, provided it covers no more than 10% of the surface area of the skin.

b) Class I

Walnut kernels in this class must be of good quality, of color not darker than light brown and/or lemon-yellow. They must be characteristic of the variety and/or commercial type. Slight defects may be allowed provided that these do not affect the general appearance of the produce, the quality, the keeping quality, or its presentation in the package.

Scuffing is allowed on:

- Quarters and all pieces; and

- Halves, provided it covers no more than 20% of the surface area of the skin.

c) Class II

This class includes kernels that do not qualify for inclusion in the higher classes but satisfy the minimum requirements specified above. Walnut kernels in this class must be of color not darker than dark brown. Darker kernels may be marketed in this class, provided the color is indicated on the package. Defects may be allowed, provided that the walnut kernels retain their essential characteristics as regards general appearance, quality, keeping quality, and presentation. This class also includes mixtures of kernels of different colors and is designated in the marking by the words 'mixed colors'.

Scuffing is not considered a defect.

Any defects negatively affecting the appearance or edibility of the kernel including:

- Staining or discoloration: Abnormal coloration which covers more than one-eighth of the surface of the kernel and which is of color in pronounced contrast with the color of the rest of the kernel (dark blemishes or areas of discoloration);

- Embedded dirt: Kernels or portions of kernels with dirt or other foreign material embedded into the flesh of the kernel;

- Crushing of more than 5% of the volume of the kernel; and

- Drying defect: The kernel is moist, soft, or leathery.

• Fragments: Kernel and skin fragments that can pass through a sizing screen of 3 mm diameter.
• Shell: Outer shell and/or woody partition from between the halves of the kernel (internal central partition), and any fragments of either.
• Shriveled kernels: Kernel which is seriously shrunken, wrinkled, and tough.
• Mold: Mold filaments visible to the naked eye.
• Decay: Significant decomposition caused by the action of microorganisms.
• Insect damage: Visible damage caused by insects or other animal parasites in the presence of dead insects or insect debris.
• Foreign matter: Any matter or material not usually associated with the product.
• Mineral impurities: Acid insoluble ash.
• Rancidity: Oxidation of lipids or free fatty acid production producing a disagreeable flavor.
• Foreign smell/taste: Any odor or flavor that is not characteristic of the product.

Walnut kernels must be packed in such a way as to protect the produce properly. If wooden packaging is used, the product must be separated from the bottom, sides, and lid by paper or suitable protective material. The materials used inside the package must be new, clean, and of a quality such as to avoid causing any external or internal damage to the produce. The use of materials and particularly of paper or stamps bearing trade specifications is allowed provided that the printing or labeling has been done with non-toxic ink or glue. Kernels may be packed in airtight sealed containers, in a vacuum, or in inert gas.

Factors that affect walnut price are harvest yield, processing method, and form of walnut including in-shell, shelled, and hand-cracked / machine-cracked.

The factors are further explained as follows:

Supply

- Policy: Changed regulations to inspect and certify the end-products and by-products will impact the decrease of the walnut meal price and improve the manufacturing process by:

(1) Eliminating the need for multiple inspections for the same product (walnut meal).

(2) Improve processor efficiencies by eliminating duplicative inventory tracking.

Demand

• Health Information: Information regarding the new beneficial functions of walnuts. In Indian cases, for instance, information on walnuts as a remedy for knee pain increased the demand by more than 25%. The wholesale price of walnut in-shell has also surged 17-20%.

• Substitution Goods: The emergence of substitution goods such as acorns, almonds, peanuts, and chestnuts, also affects the demand as well as the market price of walnuts.

• Exchange Rate: The U.S. dollar exchange rate certainly affects the market price for walnuts. When the U.S. dollar experiences depreciation, goods become cheap, accompanied by an increase in demand and an impact on prices.

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