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United States Standards

for Grades of Walnuts 

(Juglans regia) in the 

Shell

September 21, 2017
This issue of the United States Standards for Grades of Walnuts (Juglans regia) in 

the Shell (82 FR 39655) supersedes the previous issue which has been in effect 

since November 15, 1976.

Voluntary U.S. grade standards are issued under the authority of the Agricultural 

Marketing Act of 1946, which provides for the development of official U.S. grades to 

designate different levels of quality. These grade standards are available for use by 

producers, suppliers, buyers, and consumers. As in the case of other standards for 

grades of fresh and processed fruits, vegetables, and specialty crops these 

standards are designed to facilitate orderly marketing by providing a convenient 

basis for buying and selling, for establishing quality control programs, and for 

determining loan values. 

The U.S. grade standards and inspection instructions for all fresh and processed fruits,

vegetables, and specialty crops are available on the internet and upon request at the 

address below. These documents provide detailed interpretations of the grade standards 

and provide step-by-step procedures for grading the product. 

Grade standards are issued by the U.S. Department of Agriculture (USDA) after careful 

consideration of all data and views submitted during rulemaking. The Department 

welcomes suggestions for improving the standards in future revisions. Comments may be 

submitted to, and copies of standards and inspection instructions obtained from: 

Director, Specialty Crops Inspection Division

Specialty Crops Program, 

USDA, Agricultural Marketing Service

1400 Independence Avenue, SW, STOP 0240 

Washington, D.C. 20250

__________________________________________________________________________

Authority: 7 U.S.C. 1621-1627. 

Note: Compliance with the provisions of these standards shall not excuse failure to 

comply with the provisions of the Federal Food, Drug, and Cosmetic Act, or 

with applicable State laws and regulations.

Non-Discrimination Policy: In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights 

regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA

programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender 

expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, 

political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all 

bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. 

Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, 

American Sign Language, etc.) should contact the responsible Agency or USDA’s TARGET Center at (202) 720-2600 (voice and TTY) 

or contact USDA through the Federal Relay Service at (800) 877-8339. Additionally, program information may be made available in 

languages other than English. 

To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form, AD-3027, found online 

at http://www.ascr.usda.gov/complaint_filing_cust.html and at any USDA office or write a letter addressed to USDA and provide in the 

letter all of the information requested in the form. To request a copy of the complaint form, call (866) 632-9992. Submit your completed 

form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 

Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program.intake@usda.gov. 

USDA is an equal opportunity provider, employer, and lender.
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

1

United States Standards for Grades of Walnuts (Juglans regia) in the Shell

Section Page No.

General........................................................................................................................... 3

§51.2945 Application................................................................................................... 3

§51.2946 [Reserved]. .................................................................................................. 3

§51.2947 Method of inspection. .................................................................................. 3

Grades............................................................................................................................ 3

§51.2948 U.S. No. 1.................................................................................................... 3

§51.2949 U.S. No. 2.................................................................................................... 3

§51.2950 U.S. No. 3.................................................................................................... 4

§51.2951 [Reserved]. .................................................................................................. 4

Size Specifications........................................................................................................ 5

§51.2952 Size specifications. ...................................................................................... 5

Variety or Type Specifications ..................................................................................... 5

§51.2953 Variety or type specifications....................................................................... 5

Tolerances for Grade Defects ...................................................................................... 6

§51.2954 Tolerances for grade defects....................................................................... 6

Application of Tolerances ............................................................................................ 7

§51.2955 Application of tolerances.............................................................................. 7

Definitions...................................................................................................................... 7

§51.2956 Practically clean........................................................................................... 7

§51.2957 Bright. .......................................................................................................... 7

§51.2958 Splits............................................................................................................ 7

§51.2959 Injury by discoloration.................................................................................. 7

§51.2960 Damage....................................................................................................... 7

§51.2961 Well dried..................................................................................................... 8

§51.2962 Decay. ......................................................................................................... 8

§51.2963 Dark discoloration........................................................................................ 8
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

2

§51.2964 Rancidity...................................................................................................... 8

§51.2965 Fairly clean. ................................................................................................. 9

§51.2966 Serious damage. ......................................................................................... 9
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

3

General

§51.2945 Application.

The standards contained in this subpart apply only to walnuts commonly known as 

English or Persian walnuts (Juglans regia). They do not apply to the walnuts commonly 

known as black walnuts (Juglans nigra).

§51.2946 [Reserved].

§51.2947 Method of inspection.

In determining the grade of a lot of walnuts, all of the nuts in the sample first should be 

graded for size and then examined for external defects. The same nuts then should be 

cracked and examined for internal defects. The nuts must meet the requirements for 

both external and internal quality in order to meet a designated grade.

Grades 

§51.2948 U.S. No. 1.

“U.S. No. 1” consists of walnuts in shells which are dry, practically clean, bright and free 

from splits, injury by discoloration, and free from damage caused by broken shells, 

perforated shells, adhering hulls or other means. The kernels are well dried, free from 

decay, dark discoloration, rancidity, and free from damage caused by mold, shriveling, 

insects or other means. (See §51.2954.)

(a) Kernel color shall be specified in connection with this grade in terms of “extra 

light,” “light,” “light amber,” or “amber” from the USDA Walnut Color Chart or in 

terms of “red” color. The color classifications in the USDA Walnut Color Chart 

shall not apply to “red” color. Furthermore, “red” color shall not be mixed with 

“extra light,” “light,” “light amber,” or “amber” colors. When kernel color is based 

on the color classifications from the USDA Walnut Color Chart, at least 70 

percent, by count, of the walnuts have kernels which are not darker than “light 

amber,” and which are free from grade defects: Provided, That at least foursevenths of the above amount, or 40 percent of the walnuts have kernels which 

are not darker than “light.” Higher percentages of nuts with kernels not darker 

than “light amber” which are free from grade defects and/or higher percentages 

with kernels not darker than “light” which are free from grade defects, may be 

specified in accordance with the facts. (See §51.2954.)

(b) Size shall be specified in connection with the grade. (See §51.2952.)

§51.2949 U.S. No. 2.

“U.S. No. 2” consists of walnuts in shells which are dry, practically clean and free from 

splits, and free from damage caused by broken shells, perforated shells, adhering hulls, 
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

4

discoloration or other means. The kernels are well dried, free from decay, dark 

discoloration, rancidity, and free from damage caused by mold, shriveling, insects or 

other means. (See §51.2954.)

(a) Kernel color shall be specified in connection with this grade in terms of “extra 

light,” “light,” “light amber,” or “amber” from the USDA Walnut Color Chart or in 

terms of “red” color. The color classifications in the USDA Walnut Color Chart 

shall not apply to “red” color. Furthermore, “red” color shall not be mixed with 

“extra light,” “light,” “light amber,” or “amber” colors. When kernel color is based 

on the color classifications from the USDA Walnut Color Chart, at least 60 

percent, by count, of the walnuts have kernels which are not darker than “light 

amber,” and which are free from grade defects. Higher percentages of nuts with 

kernels not darker than “light amber” which are free from grade defects, and/or 

percentages with kernels not darker than “light” which are free from grade 

defects, may be specified in accordance with the facts. (See §51.2954.)

(b) Size shall be specified in connection with the grade. (See §51.2952.)

§51.2950 U.S. No. 3.

“U.S. No. 3” consists of walnuts in shells which are dry, fairly clean, free from splits, and 

free from damage caused by broken shells, and free from serious damage caused by 

discoloration, perforated shells, adhering hulls or other means. The kernels are well 

dried, free from decay, dark discoloration, rancidity, and free from damage caused by 

mold, shriveling, insects or other means. (See §51.2954.)

(a) Kernel color may be specified in connection with this grade in terms of “light

amber” or “light” from the USDA Walnut Color Chart or in terms of “red” color. 

The color classifications in the USDA Walnut Color Chart shall not apply to “red” 

color. Furthermore, “red” color shall not be mixed with “extra light,” “light,” “light 

amber,” or “amber” colors. When kernel color is based on the color 

classifications from the USDA Walnut Color Chart, there is no requirement in this 

grade for the percentage of walnuts having kernels which are “light amber” or 

“light.” However, the percentage, by count, of nuts with kernels not darker than 

“light amber” which are free from grade defects and/or the percentage with 

kernels not darker than “light” which are free from grade defects, may be 

specified in accordance with the facts. (See §51.2954.)

(b) Size shall be specified in connection with the grade. (See §51.2952.)

Reserved

§51.2951 [Reserved].
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

5

Size Specifications 

§51.2952 Size specifications.

Size shall be specified in accordance with the facts in terms of one of the following 

classifications:

(a) Mammoth size. Mammoth size means walnuts of which not over 12 percent, by 

count, pass through a round opening 96/64 inches in diameter;

(b) Jumbo size. Jumbo size means walnuts of which not over 12 percent, by count, 

pass through a round opening 80/64 inches in diameter;

(c) Large size. Large size means walnuts of which not over 12 percent, by count, 

pass through a round opening 77/64 inches in diameter; except that for walnuts 

of the Eureka variety and type, such limiting dimension as to diameter shall be 

76/64 inches;

(d) Medium size. Medium size means walnuts of which at least 88 percent, by 

count, pass through a round opening 77/64 inches in diameter, and of which not 

over 12 percent, by count, pass through a round opening 73/64 inches in 

diameter;

(e) Standard size. Standard size means walnuts of which not over 12 percent, by 

count, pass through a round opening 73/64 inches in diameter;

(f) Baby size. Baby size means walnuts of which at least 88 percent, by count, 

pass through a round opening 74/64 inches in diameter, and of which not over 10 

percent, by count, pass through a round opening 60/64 inch in diameter; and,

(g) Minimum diameter, or minimum and maximum diameter. In lieu of one of the 

foregoing classifications, size of walnuts may be specified in terms of minimum 

diameter, or minimum and maximum diameter: Provided, That not more than 12 

percent, by count, pass through a round hole of the specified minimum diameter, 

and at least 88 percent, by count, pass through a round hole of any specified 

maximum diameter.

Variety or Type Specifications

§51.2953 Variety or type specifications.

The variety or type of any lot, of walnuts in the shell may be specified in accordance 

with the facts as follows:

(a) If the lot is of one named variety, that variety name may be specified, Provided, 

That not over 10 percent, by count, of the walnuts in the lot are of another variety 

or type than that specified; and,
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

6

(b) If the lot is a mixture of two or more distinct varieties or types it may be specified 

as “Mixed Varieties.”

Tolerances for Grade Defects

§51.2954 Tolerances for grade defects.

In order to allow for variations incident to proper grading and handling, the following 

tolerances shall be permitted for nuts which fail to meet the requirements of the 

respective grades as indicated. Terms in quotation marks refer to color classifications 

illustrated on the color chart.

Tolerances for Grade Defects

Grade External (shell) 

defects

Internal (kernel) 

defects

Kernel color based 

on USDA Walnut 

Color Chart

Kernel color 

based on red

U.S. No. 1

10%, by count, for 

splits. 5%, by count,

for other shell 

defects, including not 

more than 3% 

seriously damaged.

10% total, by count, 

including not more 

than 6% which are 

damaged by mold or 

insects or seriously 

damaged by other 

means, of which not 

more than 5/6 or 5% 

may be damaged by 

insects, but no part 

of any tolerance shall 

be allowed for 

walnuts containing 

live insects.

No tolerance to 

reduce the required 

70% of “light amber”

kernels or the 

required 40% of 

“light” kernels or any 

larger percentage of 

“light amber” or “light”

kernels specified.

-----

U.S. No. 2

10%, by count, for 

splits. 10%, by 

count, for other shell 

defects, including not 

more than 5% 

serious damage by 

adhering hulls.

15% total, by count, 

including not more 

than 8% which are 

damaged by mold or 

insects or seriously 

damaged by other 

means, of which not 

more than 5/8 or 5% 

may be damaged by 

insects, but no part 

of any tolerance shall 

be allowed for 

walnuts containing 

live insects.

No tolerance to 

reduce the required 

60% or any specified 

larger percentage of 

“light amber” kernels, 

or any specified 

percentage of “light”

kernels.

-----

U.S. No. 3

Same as above 

tolerance for U.S. 

No. 2.

Same as above 

tolerance for U.S. 

No. 2.

No tolerance to 

reduce any 

percentage of “light 

amber” or “light”

kernel specified.

-----
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

7

Application of Tolerances

§51.2955 Application of tolerances.

The tolerances provided in these standards are on a lot basis, and they shall be applied 

to a composite sample representative of the lot. However, any identifiable container or 

group of containers in which the walnuts are obviously of a quality materially different 

from that in the majority of the containers shall be considered as a separate lot, and 

shall be sampled separately.

Definitions

§51.2956 Practically clean.

“Practically clean” means that, from the viewpoint of general appearance, the walnuts 

are practically free from adhering dirt or other foreign matter, and that individual walnuts 

are not damaged by such means. A slightly chalky deposit on the shell is characteristic 

of many bleached nuts and shall not be considered as dirt or foreign matter.

§51.2957 Bright.

“Bright” means a fairly light, attractive appearance. A slight chalky deposit on the shell 

shall not be considered as affecting brightness.

§51.2958 Splits.

“Splits” means walnuts with the seam opened completely around the nut so that the two 

halves of the shell are held together only by the kernel.

§51.2959 Injury by discoloration.

“Injury by discoloration” means that the color of the affected portion of the shell 

objectionably contrasts with the color of the rest of the shell of the individual nut.

§51.2960 Damage.

“Damage” means any specific defect mentioned in this section; or any equally 

objectionable variation of any one of these defects, any other defect, or any combination 

of defects which materially detracts from the appearance or the edible or shipping 

quality of the individual walnut or the lot as a whole. The following specific defects shall 

be considered as damage:

(a) Broken shells when the area from which a portion of the shell is missing is 

greater than the area of a circle one-fourth inch in diameter; or when the two 

halves of the shell have become completely broken apart and separated from 

each other;
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

8

(b) Perforated shells when the area affected aggregates more than that of a circle 

one-fourth inch in diameter. The term “perforated shells” means imperfectly 

developed areas on the shell resembling abrasions and usually including small 

holes penetrating the shell wall;

(c) Adhering hulls when affecting more than 5 percent of the shell surface;

(d) Discoloration (or stain) which covers, in the aggregate, one-fifth or more of the 

surface of the shell of an individual nut, and which is brown, reddish brown, gray, 

or other color in pronounced contrast with the color of the rest of the shell or the 

majority of shells in the lot, or darker discoloration covering a smaller area if the 

appearance is equally objectionable;

(e) Mold when attached to the kernel and conspicuous; or when inconspicuous 

white or gray mold affects an aggregate area larger than one square centimeter 

or one-eighth of the entire surface of the kernel, whichever is the lesser area;

(f) Shriveling when more than 5 percent of the surface of the kernel, including both 

halves, is severely shriveled, or a greater area is affected by lesser degrees of 

shriveling producing an equally objectionable appearance. Kernels which are 

thin in cross section but which are otherwise normally developed shall not be 

considered as damaged; and, 

(g) Insects when an insect or insect fragment, web or frass is present inside the 

shell, or the kernel shows distinct evidence of insect feeding.

§51.2961 Well dried.

“Well dried” means that the kernel is firm and crisp, not pliable or leathery.

§51.2962 Decay.

“Decay” means that any portion of the kernel is decomposed.

§51.2963 Dark discoloration.

“Dark discoloration” means that the color of the skin of the kernel is darker than 

“amber.” (See color chart.)

§51.2964 Rancidity.

“Rancidity” means the stage of deterioration in which the kernel has developed a rancid 

flavor. Rancidity should not be confused with a slightly astringent flavor of the pellicle 

(skin) or with staleness, the stage at which the flavor is flat but not distasteful.
United States Standards for Grades of Walnuts (Juglans regia) in the Shell 

(September 21, 2017)

9

§51.2965 Fairly clean.

“Fairly clean” means that, from the viewpoint of general appearance, the lot is not 

seriously damaged by adhering dirt or other foreign matter, and that individual walnuts 

are not coated or caked with dirt or foreign matter. Both the amount of surface affected 

and the color of the dirt shall be taken into consideration.

§51.2966 Serious damage.

“Serious damage” means any specific defect mentioned in this section; or an equally 

objectionable variation of any one of these defects, any other defect, or any combination 

of defects which seriously detracts from the appearance or the edible or shipping quality 

of the walnut. The following specific defects shall be considered as serious damage:

(a) Discoloration (or stain) which covers, in the aggregate, one-third or more of the 

surface of the shell of an individual nut and which is brown, reddish brown, gray, 

or other color in pronounced contrast with the color of the rest of the shell or the 

majority of shells in the lot, or darker discoloration covering a smaller area if the 

appearance is equally objectionable;

(b) Perforated shells when the area affected aggregates more than that of a circle 

three-eighths of an inch in diameter. The term “perforated shells” means 

imperfectly developed areas on the shell resembling abrasions and usually 

including small holes penetrating the shell wall;

(c) Adhering hulls when affecting more than one-eighth of the shell surface in the 

aggregate;

(d) Shriveling when both halves of the kernel are affected by severe shriveling over 

an area totaling more than one-eighth of the surface; or when both halves are 

affected over a greater area by lesser degrees of shriveling producing an equally 

objectionable appearance. When one of the halves of the kernel shows no 

shriveling, the kernel shall not be considered seriously damaged unless the other 

half shows shriveling to the extent that over 50 percent of its surface is severely 

shriveled, or a greater area is affected by lesser degrees of shriveling producing 

an equally objectionable appearance. Kernels which are thin in cross section, 

but which are otherwise normally developed shall not be considered as 

damaged;

(e) Rancidity or decay; and,

(f) Uncured kernels which are wet, rubbery and “green”.