THE GRADING OF COFFEE1
By Henry A. Lepper
(Editor's Note: This article is being reprinted in part from Food Control Statement
No. 26, March 16, 1931. The principles of coffee grading have not changed in
recent years, and FDA may make detentions of import coffee on the basis of the
criteria described here. The original article was prepared by H.A. Lepper
(deceased) of the Division of Food, who for many years was FDA's expert on
Unofficial grading of coffee is done by the trade on well-established principles, the result of
years of experience. The recognized imperfections are "blacks," "part blacks," "browns,"
"quakers," "sailors," "shells," pods, husks, "parchment," broken berries, sticks, and stones. There
is not a unanimity of opinion that all of these should be regarded as imperfections. Each "black"
is counted as one imperfection. The other inhibited berries and material are scored in terms of
equivalency to one "black." The relationships of the "blacks" to the other imperfections are not
definitely established and different members of the trade have a somewhat different, though not
widely divergent, understanding of them. The number of imperfections which go to fix each
grade seems to be more uniformly agreed upon. Grade 1 represents complete freedom from
imperfections. Such coffee is not an article of commerce. The several grades, as determined by
the number of imperfections present, are given in Table 1. Each grade is separated from the other
by 50 points and the number of imperfections for intermediate grades at five point intervals also
given. The size of the sample on which the count of imperfections is made is not of uniform
practice in the trade. This will be referred to later. In trade or in official exchange gradings the
imperfections are counted up to grade 7. From grades 7 to 8 and lower, grading is done by visual
comparison with standard exchange type grade samples, the intermediate points being estimated.
Description of Kinds of Coffee Berries and Foreign Material
Sound Coffee - The berries are generally smooth, of waxy appearance, ranging from light yellow
to dark green in color.
Blacks - These, as the name indicates, are black in color. They are of two classes:
(1) Those of smooth, waxy appearance, not unlike sound coffee but black in color
(2) Those shriveled and black
Part Blacks - These are sound in part and have black areas ranging from small spots to almost the
Browns - These resemble the blacks, there being both waxy and shriveled types. They are
decidedly brown in color.
Lepper, H.A. FDA By-Lines, Vol. 7, No. 6, May 1977. pp 285-291.
Number of "Blacks" (Imperfections) for Grades of Coffee From 1 to 9 With Intermediate Grades
of Five Points Each
Grade "Blacks" Grade "Blacks" Grade "Blacks" Grade "Blacks"
1 None 3 13 5 58 7 200
1-05 2+45 3/5 3-05 4+45 14 7/10 5-05 6+45 64 7-05 8+45 225
1-10 2+40 1 1/5 3-10 4+40 16 2/5 5-10 6+40 70 7-10 8+40 250
1-15 2+35 1 4/5 3-15 4+35 18 1/10 5-15 6+35 76 7-15 8+35 275
1-20 2+30 2 2/5 3-20 4+30 19 4/5 5-20 6+30 81 7-20 8+30 300
1-25 2+25 3 3-25 4+25 21 1/2 5-25 6+25 87 7-25 8+25 325
2+20 1-30 3 3/5 4+20 3-30 23 1/5 6+20 5-30 92 8+20 7-30 350
2+15 1-35 4 1/5 4+15 3-25 24 9/10 6+15 5-35 98 8+15 7-35 375
2+10 1-40 4 4/5 4+10 3-40 26 3/5 6+10 5-40 103 8+10 7-40 400
2+05 1-45 5 2/5 4+05 3-45 28 3/10 6+05 5-45 109 8+05 7-45 425
2 6 4 30 6 115 8 450
2-05 3+45 6 7/10 4-05 5+45 32 4/5 6-05 7+45 123 8-05 9+45 490
2-10 3+40 7 2/5 4-10 5+40 35 3/5 6-10 7+40 132 8-10 9+40 530
2-15 3+35 8 1/10 4-15 5+35 38 2/5 6-15 7+35 140 8-15 9+35 570
2-20 3+30 8 4/5 4-20 5+30 41 1/5 6-20 7+30 149 8-20 9+30 610
2-25 3+25 9 1/2 4-25 5+25 44 6-25 7+25 157 8-25 9+25 650
3+20 2-30 10 1/5 5+20 4-30 46 4/5 7+20 6-30 166 9+20 8-30 690
3+15 2-35 10 9/10 5+15 4-35 49 3/5 7+15 6-35 174 9+15 8-35 730
3+10 2-40 11 3/5 5+10 4-40 52 2/5 7+10 6-40 183 9+10 8-40 770
3+05 2-45 12 3/10 5+05 4-45 55 1/5 7+05 6-45 191 9+05 8-45 810
Quakers - "Blights" is a name also applied to these shriveled berries, ranging in color from light
yellow or green to very light brown. Some of the darker colored are difficult to distinguish from
shriveled "browns," but this need cause no confusion, as their relative weight in grading is the
Sailors - As the name intimates, these berries float. They are white or nearly white, not having
the waxiness of normal coffee, appearing as though deficient in fat.
"Shells" - The name, in this case, is descriptive, as these berries resemble the conch shell. Their
usual appearance is that of sound coffee.
Broken - These are pieces of broken berries, both sound and unsound.
Pods - These are the whole coffee fruit (the "cherry"), consisting of pulp, parchment layer, silver
skin, with the seeds (or berries) inside, all of which have been dried together. They are deep,
dark red to almost black in color.
Husks - These are pieces of the dried pulp which have become separated from pods.
Parchment - The name, in this case, classifies the material. It consists of the light yellow, thin,
translucent, horny pieces, resembling parchment. They come from the layer enclosing the seeds
in the fruit, when dried pods become broken in the coffee.
Sticks - These are small pieces of twigs or of charcoal.
Stones - Pieces of hard earth or rock, of varying colors and sizes, are classed as stones.
It is a difficult task to separate the various imperfections from a sample of coffee on the sole
basis of a verbal description, but with actual separations of known classification as examples, the
grading of coffee should be much simplified.
Grading Under the Food and Drugs Act
As has previously been stated, no definite or exact knowledge is available on the composition of
exchange grade 8. In applying Food Inspection Decision 108 to coffee imports, it does not
appear to be necessary that this guide to quality be strictly followed. It is desirable, in view of the
fact that the grade has been announced as a guide, that grading be done in such manner that only
coffees of lower than grade 8 be the subject of rejected entry. It is of importance that the grading
done in the various port laboratories be uniform, so that action on coffee will be the same at each
port. The results of analysis and cup tests on the various imperfections show that "blacks,"
"browns," and "quakers" can be regarded as definitely objectionable when offered as coffee. This
conclusion is backed by trade opinion. "Part Blacks" are also considered objectionable by the
trade. While analysis does not indicate that much objection is to be taken to "sailors," cup tests
show this separation to be of little coffee value. The trade, however, does not raise objection to
this type of berry, inasmuch as it has only the effect of thinning the brew, without adding
anything of detrimental character. It is reasonable, therefore, to limit the amounts of the various
imperfections, with the possible exception of the "sailors," which should be present in a lot of
coffee. Foreign material, such as pods, husks, sticks and stones, is naturally not coffee and
should also be restricted. If the limiting values set by a system of grading devised for import
work are such that coffee rejected will be below grade 8 of the trade, all requirements will
apparently be met. Such grading will operate to shut out all coffees which can be regarded as
trash. It will have the support of the coffee trade. Coffees below exchange grade 8 are not
deliverable on exchange.
Determination of the Grade
A composite sample is taken by trier from a representative number of bags in a lot. In the routine
inspection of coffee shipments the examiner can familiarize himself with the general appearance
of a grade 8 type and decide, in many instances, from visual examination whether a sampling for
grading by count is necessary.
From 100 grams of the well-mixed sample, the various imperfections and the sound berries are
separated into groups. "Shells," "sailors," and sound, broken berries are regarded as
unobjectionable. Separation can be readily accomplished after the grader has familiarized
himself with the type separations. If there appears to be doubt regarding a given berry, and close
comparison with the types fails to classify it, it should be regarded as sound. Often the true
character of the doubtful berry can be ascertained by cutting transversely through the berry with
a sharp knife. The soundness of the berry is readily judged from the internal appearance.
Sometimes berries are encountered which appear to show discoloration (usually brown), but
close examination shows the abnormal appearance to be confined to an adhering thin membrane,
an unremoved "silver skin." On scraping with a knife, the berry beneath the skin is found to be
sound. Care must be exercised not to classify such berries as unsound. Experience soon permits
the grader to readily recognize these berries, as they almost always show their true character at
some point by a break in the "silver skin." The "silver skin" is removed in the preparation of the
coffee for the market, so that such misleading berries will be exceptional.
Occasionally a berry is found which is discolored by reason of visible mold growth. When
present in numbers as a result of water damage, the coffee is adulterated and no grading is
attempted. The occasional moldy berry is regarded as an imperfection. Berries showing evidence
of insect infestation are not classified in grading. Coffees containing numbers of such berries are
regarded as adulterated.
Broken pieces of discolored berries ("blacks," "browns") are pieced together to approximately
form whole berries and each of such reconstructed berries is counted as one "black" or "brown,"
as the case may be. Pieces of husk and parchment are counted together. The pieces are grouped
in units approximately equal to that found on a pod. Each unit is then counted as one pod. Berries
which are partially discolored (with the exception of black discoloration) or which are shriveled
at one end, less than one-half berry, are exceptional and usually disregarded. In those rare
instances where a sample consists, in large part, of this kind of berry it needs special
consideration, as it is not easily graded. Samples of this kind are seldom encountered. One
sample has come to our attention consisting of many berries which were brown and shriveled at
one end and this was identified by a number of the trade as a frosted coffee.
After the imperfections are grouped, the number of each is counted and the counts evaluated in
terms of "blacks" from the table of equivalents. This table agrees substantially with trade
The total number of imperfections in the 100 grams, in terms of "blacks," is multiplied by the
arbitrary factor 3.7. The result is located in Table 1 and the corresponding grade is the grade of
Table of Equivalents
"Blacks" (waxy or shriveled) 1 equals 1 "black"
"Part Blacks" (one-half or more black) 1 equals 1 "black"
"Part Blacks" (less than one-half black) 2 equal 1 "black"
"Moldy" 2 equal 1 "black"
"Brown" (waxy or shriveled) 5 equal 1 "black"
"Quakers" 5 equal 1 "black"
Pods 1 equals 1 "black"
Husks and "Parchment" (equivalent to a pod) 1 equals 1 "black"
Sticks (approximately the length of a coffee berry) 1 equals 1 "black"
Sticks (pieces of charcoal the size of coffee berry) 1 equals 1 "black"
Stones (size of coffee berry) 1 equals 2 "blacks"
Sticks and stones larger or smaller in size are evaluated proportionately.
Discussion of the Factor
It has already been pointed out that there is no definitely established weight of sample on which
the count of imperfection in terms of "blacks" is made, to determine the grade by Table 1. Some
members of the trade refer to it as being 1 pound, and others as a "pan." A "pan" is found to hold
about 13 ounces. With the table of equivalents as used herein, the count of the imperfections in
terms of "blacks" in a whole can of the sample gives an average result of 450, the figure in Table
1 for grade 8. The factor 3.7 which converts 100 grams to 13 ounces is, therefore, appropriate.
Example of Grading Results
Type of Imperfection No. Equivalent Blacks
"Blacks" 58 58
"Part Blacks" 8 4
"Browns" 140 28
"Quakers" 26 5
Pods 2 2
Husks and "Parchment" 4 4
Sticks 4 5
Stones 3 5
Total imperfections 111
Total x 3.7 411
An 8+10 grade is 10/50 better than an 8. It is the same as a 7-40
This grading procedure has been used for a number of years and has not resulted in the detention
of coffees which would be graded by the trade as better than 8. Applied to five samples of
exchange type 8, three as of March 1930, and two as of February 1929, grades of 8 - 20, 8 - 05, 8
+ 5, 8 - 10, and 8 + 10, respectively, were found. In recognition of the fact that this method of
grading does not grade a sample in exact keeping with the manner in which exchange grades are
established, action is not recommended on samples grading better than 8 - 20.