United States

Department of

Agriculture

Agricultural 

Marketing

Service

Fruit and

Vegetable

Division

Fresh

Products

Branch

United States Standards

for Grades of

Potatoes for Processing

Effective April 14, 1983

(Reprinted - January 1997)
 Compliance with the provisions of these standards shall not excuse failure to comply with provisions of applicable 1

Federal or State laws.

1

United States Standards for Grades of Potatoes for Processing 1

51.3410 Grades. 

51.3411 Usable piece. 

51.3412 Unusable material. 

51.3413 Size. 

51.3414 Application of standards. 

51.3415 Definitions. 

51.3416 Classification of defects. 

51.3417 Optional test for specific gravity. 

51.3418 Optional test for fry color. 

§51.3410 Grades. 

(a) "U.S. No. 1 Processing" consists of potatoes which meet the following requirements: 

(1) Basic requirements: 

(i) Similar varietal characteristics; 

(ii) Moderately firm; and, 

(iii) Fairly well shaped.

(2) Free from: 

(i) Freezing or freezing injury; 

(ii) Blackheart; 

(iii) Late Blight Tuber Rot; 

(iv) Southern Bacterial Wilt; 

(v) Bacterial Ring Rot; 

(vi) Insects, worms or larvae; 

(vii) Soft rot and wet breakdown; and, 

(viii) Loose sprouts, dirt and foreign material.

(3) Free from damage by any cause. 

(4) Size. Unless otherwise specified, individual potatoes shall be not less than 2 inches in diameter

or 4 ounces in weight. Percentage(s) of a larger size(s) and/or a maximum size may be specified. 

(b) "U.S. No. 2 Processing" consists of potatoes or usable pieces of potatoes which meet the

following requirements: 

(1) Basic requirements: 

(i) Similar varietal characteristics; 

(ii) Moderately firm; and, 

(iii) Not seriously misshapen. 

(2) Free from:

(i) Freezing or freezing injury;
2

(ii) Blackheart;

(iii) Late Blight Tuber Rot;

(iv) Southern Bacterial Wilt;

(v) Bacterial Ring Rot;

(vi) Insects, worms or larvae;

(vii) Soft rot and wet breakdown; and,

(viii) Loose sprouts, dirt and foreign material.

(3) Free from serious damage by any cause.

(4) Size. Unless otherwise specified, whole potatoes shall be not less than 1-1/2 inches in

diameter, or usable pieces shall be not less than 4 ounces in weight. Percentage(s) of a larger

size(s) and/or maximum size may be specified.

§51.3411 Usable piece.

"Usable Piece" means that portion of the potato remaining after trimming, or as it occurs in the

sample.

(a) Not have any unusable material;

(b) Unless otherwise specified, weigh at least 4 ounces; and,

(c) Must have at least 50% of peel remaining after trimming.

§51.3412 Unusable material.

"Unusable Material" consists of defective portions of potatoes, and potatoes which are frozen,

affected by freezing injury, soft rot, wet breakdown, insects, worms, larvae, Blackheart, Late

Blight Tuber Rot, Southern Bacterial Wilt, Bacterial Ring Rot, or which are seriously damaged by

internal defects.

§51.3413 Size.

(a) The minimum size, maximum size or range in size may be specified in connection with the

grade in terms of diameter or weight.

(b) Diameter means the greatest dimension in terms of inches or fractions of an inch measured at

right angles to the longitudinal axis, without regard to the position of the stem-end.

(c) Weight means the minimum or maximum weight measured in terms of whole ounces. When a

maximum weight is specified, the potato shall not be considered as oversize until it weighs the

next higher ounce.

§51.3414 Application of standards.

In the application of these standards to determine the percentages of potatoes in any lot which

meet the requirements of the respective grades or size categories, tolerances do not apply.

However, for lots which are graded or pre-sorted for size or quality, offered for inspection and

required to meet one of the grades, the following tolerances, by weight, are provided:

(a) For defects:

(1) U.S. No. 1 Processing: 10 percent for potatoes which fail to meet the requirements of this

grade including not more than one-half of this tolerance, or 5 percent, for serious damage by any

means, including therein not more than 2 percent for potatoes which are frozen or affected by soft

rot or wet breakdown.

(2) U.S. No. 2 Processing: 10 percent for potatoes which fail to meet the requirements of this

grade including not more than one-half of this tolerance, or 5 percent, for potatoes which are

seriously damaged by internal defects occurring entirely within the vascular ring, including therein
 USDA Visual Aid, POT-L 1 Jan 81. This publication may be examined in the Fruit and Vegetable Division, Fresh 2

Products Branch, AMS, U.S. Department of Agriculture, South Building, Washington, DC 20250, or any field office of

the Fresh Fruit and Vegetable Inspection Service. Copies of this visual aid may be purchased from the John Henry

Company, P.O. Box 17099, Lansing, MI 48901 or United Fresh Fruit and Vegetable Association, N. Washington at

Madison, Alexandria, VA 22314.

3

not more than 2 percent for potatoes which are frozen or affected by soft rot or wet breakdown.

(b) For loose sprouts, dirt and foreign material: 2 percent.

(c) For off-size:

(1) Undersize: 3 percent when the minimum size specified is less than 2-1/4 inches in diameter or

less than 5 ounces in weight; and 5 percent when the minimum size specified is 2-1/4 inches or

more in diameter or 5 ounces or more in weight.

(2) Oversize: 10 percent.

§51.3415 Definitions.

"Similar varietal characteristics" means that the potatoes in any lot have the same general shape,

color, and character of skin and color of flesh.

"Fairly well shaped" means that the potato is not materially pointed, dumbbell-shaped, or

otherwise deformed.2

"Moderately firm" means that the potato is not seriously shriveled or flabby.2

"Not seriously misshapen" means that the potato is not seriously deformed and causing more than

10% waste when determining the non-peelable area directly due to shape.

"Soft rot or wet breakdown" means any soft, mushy or leaky condition of the tissue such as Leak,

slimy soft rot, wet type Fusarium Tuber Rot, or wet breakdown following freezing injury or heat

injury.

"Loose sprouts, dirt and foreign material" means unattached sprouts or sprouts that become

detached during the grading of the sample, stems, vines, adhering dirt, loose dirt, stones, trash and

other extraneous material.

"Damage" means any defect listed in §51.3416, or an equally objectionable variation of any one of

these defects, any other defect, or any combination of defects, which cannot be removed without

a loss of more than 5 percent of the total weight of the potato.

"Serious Damage" means any defect listed in §51.3416, or an equally objectionable variation of

any of these defects, any other defect, or any combination of defects, which cannot be removed

without a loss of more than 10 percent of the total weight of the potato.

"External Defects" are defects which can be detected externally. Cutting may be required to

determine the extent of the injury.

"Internal Defects" are defects which cannot be detected without cutting the potato. 
4

§51.3416 Classification of defects.

 External Defects

Defects Maximum Maximum allowed for

allowed for U.S. U.S. No. 2 processing

No. 1

processing

Air cracks........... 5% waste....... 10% waste.

Blackleg.............. 5% waste....... 10% waste.

Bruises............... 5% waste....... 10% waste.

Cuts................... Smooth, not Smooth, not more than

Enlarged lenticels, 5% waste....... 10% waste.

discolored or sunken.

Flea Beetle..........

Folded end.......... 5% waste....... 10% waste.

Fusarium tuber rot. 5% waste....... 10% waste.

Grass, wireworm... 5% waste...... 10% waste.

Greening, light..... 5% waste...... 10% waste.

Growth cracks...... 5% waste...... 10% waste.

Grub.................. No. 2.

Ingrown sprouts.... 5% waste...... 10% waste.

Nematodes.......... 5% waste...... 10% waste.

Rhizoctonia, solid or 5% waste...... 10% waste.

thick mounded. Not more than Not more than 25% of

Rodent, bird damage.

Scab, pitted......... 5% waste...... 10% waste.

Scab, russet.........

Scab, surface....... 25% of surface 50% of surface or

Scab, surface 25% of surface 50% of surface or

(elephant hide). or 5% waste. 10% waste.

Second growth...... 10% of surface 25% of surface or

Scaling, surface or 5% waste. 10% waste.

cracks -- when 5% waste....... 10% waste.

cracked, thick and 10% of surface 25% of surface or

has depth. or 5% waste. 10% waste.

Sunburn.............

Sunken discolored

areas 5% waste....... 10% waste.

more than 10% 1/3 of surface.

of surface.

See Footnote 10% waste.

10% of surface. surface.

5% waste....... 10% waste.

 or 5% waste. 10% waste.

5% waste....... 10% waste.

______________________________

USDA Visual Aid, POT-L 1 Jan 81. This publication may be examined in the Fruit and Vegetable Division, Fresh Products Branch, AMS, U.S. 2

Department of Agriculture, South Building, Washington, DC 20250, or any field office of the Fresh Fruit and Vegetable Inspection Service. Copies of

this visual aid may be purchased from the John Henry Company, P.O. Box 17099, Lansing, MI 48901 or United Fresh Fruit and Vegetable

Association, N. Washington at Madison, Alexandria, VA 22314.
 Note: Or correspondingly lesser or greater areas in smaller or larger potatoes. 1

5

 Internal Defects

Defects Maximum Maximum allowed for

allowed for U.S. U.S. No. 2 processing

No. 1

processing

Occurring outside of or not entirely confined to the vascular ring

Internal Black Spot, 5% waste....... 10% waste.

Internal 5% waste....... 10% waste.

Discoloration, 5% waste....... 10% waste.

Vascular Browning, 5% waste....... 10% waste.

Fusarium Wilt, Net 5% waste....... 10% waste.

Necrosis, Other 5% waste....... 10% waste.

Necrosis, Stem End 5% waste....... 10% waste.

Browning. 5% waste....... 10% waste.

Occurring entirely within the vascular ring

Hollow Heart or Area affected Area affected not to

Hollow Heart with not to exceed exceed that of a circle

Discoloration. that of a circle 1-1/4 inches in diameter

Light Brown Area affected exceed that of a circle

Discoloration not to exceed 1-1/4 inches in diameter

(Brown Center). that of a circle in a 10 ounce potato.

Internal Brown Spot Not more than scattered spots 1/8 inch

and similar the equivalent of in diameter in a potato 6

discoloration 3 scattered spots ounces in weight or 2-

(Heat Necrosis). 1/8 inch in 1/2 inches in diameter

7/8 inch in in a 10 ounce potato.

diameter in a 10

ounce potato.1

diameter in a 10

ounce potato. Not more than the 1

diameter in a or correspondingly

potato 6 ounces lesser or greater number

in weight or 2- of spots in smaller or

1/2 inches in larger potatoes.

diameter, or

correspondingly

lesser or greater

number of spots

in smaller or

larger potatoes.

1

Area affected not to

1

7/8 inch in

equivalent of 6
 The hydrometer is available from the Potato Chip/Snack Food Association, Crystal Square-3, Suite 903, 1735 3

Jefferson Davis Highway, Arlington, VA 22202.

 To apply correction factor, change, actual specific gravity reading by adding or subtracting the appropriate factor 4

according to the plus or minus sign.

6

§51.3417 Optional test for specific gravity.

Tests to determine specific gravity shall be made in accordance with the procedures set forth in

this section.

(a) The potatoes used for such determinations shall be:

(1) Taken at random from a composite sample drawn from containers representative of the lot.

(2) A comparable sample from a bulk load or storage bin.

(3) From a portion of the divided sample initially drawn or submitted for determination of grade

or contract compliance.

(4) Representative of the lot with respect to size and quality.

The specific gravity for any lot of potatoes shall be the average of at least 3 corrected readings on

separate tests from the composite sample. Specific gravity may also be determined, if requested,

in accordance with size classifications or weighted value in proportion to size and/or grade

separations in the lot.

(b) Specific gravity shall be determined by either;

(1) Calculation from the weights of the sample in air and in water made with USDA approved

equipment. The reading obtained from each test shall be corrected for temperature variations

using Table I.

(2) A hydrometer specifically designed for determining the specific gravity of potatoes.3

The pulp temperature of the potatoes and the temperature of water shall be recorded immediately

before testing and the specific gravity reading corrected using Table I.

Table I.-- Correction Factors for Specific Gravity of Potatoes4

[Corrected to zero at 50 F potato temperature and 50 F water temperature] o o

Tuber 38 40 45 50 55 60 65 70 75 80

temp

o o o o o o o o o o

38 ....... -.0021 -.0020 -.0018 -.0018 -.0020 -.0023 -.0029 -.0038 -.0047 -.0056 o

40 ....... -.0017 -.0016 -.0014 -.0014 -.0016 -.0019 -.0025 -.0034 -.0043 -.0052 o

45 ....... -.0009 -.0008 -.0006 -.0006 -.0008 -.0011 -.0017 -.0026 -.0035 -.0044 o

50 ....... -.0003 -.0002 0000 0000 -.0002 -.0005 -.0011 -.0020 -.0029 -.0038 o

55 ....... +.0001 +.0002 +.0004 +.0004 +.0002 -.0001 -.0007 -.0016 -.0025 -.0034 o

60 ....... +.0004 +.0005 +.0007 +.0007 +.0005 +.0002 -.0004 -.0013 -.0022 -.0031 o

65 ....... +.0005 +.0006 +.0008 +.0008 +.0006 +.0003 -.0003 -.0012 -.0021 -.0030 o

70 ....... +.0006 +.0007 +.0009 +.0009 +.0007 +.0004 -.0002 -.0011 -.0020 -.0029 o
7

75 ....... +.0007 +.0008 +.0010 +.0010 +.0008 +.0005 -.0001 -.0010 -.0019 -.0028 o

80 ....... +.0008 +.0009 +.0011 +.0011 +.0009 +.0006 0000 -.0009 -.0018 -.0027 o

85 ....... +.0009 +.0010 +.0012 +.0012 +.0010 +.0007 +.0001 -.0008 -.0017 -.0026 o

90 ....... +.0010 +.0011 +.0013 +.0013 +.0011 +.0008 +.0002 -.0007 -.0016 -.0025 o

95 ....... +.0011 +.0012 +.0014 +.0014 +.0012 +.0009 +.0003 -.0006 -.0015 -.0024 o

100 .... +.0012 +.0013 +.0015 +.0015 +.0013 +.0010 +.0004 -.0005 -.0014 -.0023 o

When requested to convert the weight in water of 5000 gram samples used in the weight in air

versus weight in water method of specific gravity determinations, the conversion to total solids

shall be based on Table II.

Table II. -- Specific Gravity Conversion Chart for 5,000 Grams of Potatoes

Water Weight Specific Total Solids

Gravity

300............ 1.0638 17.2

310............ 1.0661 17.7

320............ 1.0684 18.2

322............ 1.0688 18.3

324............ 1.0693 18.4

326............ 1.0697 18.5

328............ 1.0702 18.6

330............ 1.0707 18.7

332............ 1.0711 18.8

334............ 1.0716 18.9

336............ 1.0720 19.0

338............ 1.0725 19.1

340............ 1.0730 19.2

342............ 1.0734 19.3

344............ 1.0739 19.4

346............ 1.0743 19.5

348............ 1.0748 19.6

350............ 1.0753 19.7

352............ 1.0757 19.8

354............ 1.0762 19.9

356............ 1.0766 20.0

358............ 1.0771 20.1

360............ 1.0776 20.2

362............ 1.0780 20.3

364............ 1.0785 20.4

366............ 1.0790 20.5

368............ 1.0794 20.6
 Munsell Color Standards for Frozen French Fried Potatoes, Third Edition, 1972, 64 - 1, may be purchased from the 5

Munsell Color Co., 2441 North Calvert St., Baltimore, MD 21218.

8

370............ 1.0799 20.7

372............ 1.0804 20.8

374............ 1.0808 20.9

376............ 1.0813 21.0

378............ 1.0818 21.1

380............ 1.0822 21.2

382............ 1.0827 21.3

384............ 1.0832 21.4

386............ 1.0836 21.5

388............ 1.0841 21.6

390............ 1.0846 21.7

392............ 1.0851 21.8

394............ 1.0855 21.9

396............ 1.0860 22.0

398............ 1.0865 22.1

400............ 1.0870 22.2

402............ 1.0874 22.3

404............ 1.0879 22.4

406............ 1.0884 22.5

408............ 1.0888 22.6

410............ 1.0893 22.7

412............ 1.0898 22.8

414............ 1.0903 22.9

416............ 1.0908 23.0

418............ 1.0912 23.1

420............ 1.0917 23.2

422............ 1.0922 23.4

424............ 1.0926 23.5

426............ 1.0931 23.6

428............ 1.0936 23.7

430............ 1.0941 23.8

432............ 1.0946 23.9

440............ 1.0965 24.4

450............ 1.0989 24.9

460............ 1.1013 25.4

470............ 1.1040 26.0

Whenever the recorded water weight for an individual reading falls between two sets of numbers

as indicated in Table II, the next higher reading shall be used.

§51.3418 Optional test for fry color.

Fry color may be determined in accordance with contract specifications by using the Munsell

Color Standards for Frozen French Fried Potatoes, Third Edition, 1972, 64 - 1. Select a 5

minimum of twenty (20) potatoes at random from the official sample. Slice each potato from stem

to blossom-end into 1/2 square inch strips. Unless otherwise specified, fry center cut strips in oil

for a minimum of 3 minutes at 350 F or 2-1/2 minutes at 375 F. o o