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Chapter 24
Grading and Classes
INTRODUCTION
Market quality is identified when a grade is established for a product. One of the main objectives of a grading system is to ensure uniform quality so that products can be priced to satisfy the interests of both the producer and the consumer. The grading standards employed and the ability of the handling or distribution system to maintain these standards until the product (especially a food product) is delivered to the customer determines the degree to which this objective is met.
Market quality is identified when a grade is established for a product. One of the main objectives of a grading system is to ensure uniform quality so that products can be priced to satisfy the interests of both the producer and the consumer. The grading standards employed and the ability of the handling or distribution system to maintain these standards until the product (especially a food product) is delivered to the customer determines the degree to which this objective is met.
Canada has an international reputation as a producer
of high quality wheat. This reputation has been maintained and protected
since 1874 by a central authority that has been guided by various
Acts of Parliament. The Canadian Grain Commission has regulated
the grading of wheat in Canada since 1912 under authority empowered
by the Canada Grain Act. The Canadian Grain Commission also regulates
grain handling in Canada in the interests of grain producers.
Wheat production on the Canadian prairies was restricted to seven classes in 1995.1. Canada Western Red Spring
2. Canada Western Amber Durum
3. Canada Western Soft White Spring
4. Canada Western Extra Strong Red Spring
5. Canada Prairie Spring Red
6. Canada Prairie Spring White
7. Canada Western Red Winter
With the exception of durum wheat, spring and winter wheat that does not meet the standards specified for the lowest scheduled grade within each class may be graded Canada Western Feed. Experimental Grades may also be established to allow the Canadian Wheat Board to test market new varieties that do not meet existing wheat class standards. A variety must be approved by Agriculture Canada before it can become eligible for experimental grades. Therefore, except for Canada Western Feed or Experimental Grades, commercial winter wheat production in western Canada is restricted to cultivars that qualify for the Canada Western Red Winter wheat class.
The Canadian grading system emphasizes:a) uniform quality,
b) high standards of cleanliness, and
c) consistent grade standards.
Wheat is graded several times as it moves through
the Canadian grain handling system to ensure that standards of quality,
cleanliness, and uniformity are maintained.
The end-use quality of a wheat sample cannot be
determined without employing elaborate testing procedures that are
time consuming and costly. However, with the exception of protein
concentration, most of the important quality characteristics of
wheat are highly dependent on the genetic make-up of the cultivar.
The Canadian wheat grading system has exploited
the relationship between grain quality and cultivar genetic make-up
to maintain quality standards. The cultivars in each market class
of wheat that can be registered for production in Canada are restricted
to those with grain quality equal or superior to reference cultivars.
Specific reference cultivars are identified in the grade specifications
of most spring wheat classes. For example, the spring wheat cultivar
Neepawa is the present standard of quality for the Canada
Western Red Spring wheat class. Quality standards are not
yet as narrowly defined for the Canada Western Red Winter
wheat class. The standard of quality for winter wheat is any variety
of red winter wheat equal to acceptable reference cultivars.
Restrictive cultivar release is effective in maintaining
quality standards within a wheat class. However, because the genetic
potential for quality is not stamped on each kernel, a problem arises
when farmers deliver cultivars representing different wheat classes
that must be segregated (identity preserved) as they move through
the grain handling system. A question of farmer and grain handler
integrity enters the grading picture at this point.
In Australia, which also exports wheat of recognized
high quality, cultivars are identified and segregated into grade
classes based on farmer affidavits that declare the name of the
cultivar at the time of delivery. A much more paternalistic attitude
exists in Canada where a cumbersome, highly subjective method of
cultivar segregation based on kernel identification is employed.
Under this system, all cultivars in each quality class must have
similar kernel characteristics so that wheat classes can be "eyeballed"
when the farmer delivers wheat to the local elevator or inland terminal.
The system of visual identification of wheat classes has been ineffective
in preventing nonregistered cultivars from being produced in western
Canada. In addition, the kernel characteristics employed to identify
wheat classes have no bearing on end-use quality. Consequently,
the added burden and restrictions resulting from the need to visually
distinguish quality classes has constantly frustrated the efforts
of plant breeders to develop improved cultivars for western Canadian
farmers. For example, a high quality, rust resistant winter wheat
with a 50 percent yield advantage over the best commercially available
cultivars could not be registered and grown in Canada if it had
kernel characteristics that were similar to those of cultivars in
the hard red spring wheat class.
Wheat price is affected by dockage, foreign material
content, and uniformity of shipments. Consequently, the Canadian
grading system has stringent regulations on the cleanliness and
uniformity of both domestic and export wheat.
Dockage
Dockage is normally left in wheat until it is received by a terminal elevator where grain is cleaned to export standards. Therefore, because farmers are paid for wheat and not dockage, official procedures have been developed to determine the amount of dockage in each truck load of wheat farmers deliver. When farmers deliver their wheat to the elevator, it is weighed and an average sample is taken as the wheat is unloaded. This average sample is then used to determine grade and dockage. Dockage is determined as a percentage of the wheat sample. The percentage dockage in the sample is then used to determine the amount of dockage that should be deducted from the gross weight to give the net weight of the wheat delivered by the farmer.
Wheat grade is determined on clean samples. Therefore,
dockage must be removed before the sample is graded.
Dockage of wheat is determined using approved cleaning equipment that includes the following:No. 10 X 10 wire sieve,
No. 5 or No. 6 Buckwheat sieve,
Carter dockage tester or Emerson kicker.The sieve that cleans the grain to grade standards and leaves the largest amount of whole grain is used to determine dockage.
Dockage removed during cleaning at terminal elevators
is usually graded as screenings and sold for livestock feed. There
are several grades of screenings that are dependent on the composition
of the material cleaned from the wheat. Screenings may receive additional
cleaning to separate out saleable components thereby increasing
the value of what was originally dockage in the farmers wheat.
Any material other than wheat that remains in the
sample after the removal of dockage is designated foreign material.
Foreign material in wheat includes rye, barley, oats, triticale,
seeds other than cereal grains, ergot, dirt, fertilizer, stones,
and roughage such as chaff, threshed wheat heads, etc. Each wheat
grade has specific tolerance levels for foreign material.
Winter wheat that does not meet Canada Western,
Feed, or Experimental grade specifications is only eligible for
off-grades and screenings grades. These grades are also known as
sample grades and the major degrading factor forms part of the grade
name. For example, wheat that contains more that 0.25 percent ergot
would be graded Sample C.W., Account Ergot.
Uniformity and consistency of quality are important
factors in maintaining confidence in a product. In the Canadian
grading system, standard samples are used as guides to ensure uniformity
and consistency of wheat grades. Each crop year, primary and export
standard samples of grain are prepared by the Grain Standards Committees
of the Canadian Grain Commission.
Primary standard samples represent the minimum quality
of each grade based on the predominant grading factors of each year's
wheat crop. They are used as visual guides to grade wheat up to
the time it is received at terminal elevators.
Export standard samples are used to determine the
grade of wheat after it has been processed in terminal elevators.
These samples are employed to ensure that the customer receives
wheat that is close to the average quality of the grade.
The quality of wheat will deteriorate if it is stored
at a high moisture content, especially if storage conditions are
warm. For this reason, each wheat grade is subdivided on the basis
of grain moisture content. Wheat that contains 14.6 percent or more
moisture is first graded on the basis of other grading factors.
The term tough or damp is then
added to the grade name to identify the moisture range at the time
of sampling.
Straight = less than 14.6 percent moisture
Tough = 14.6 to 17.0 percent moisture
Damp = over 17.0 percent moisture
The Canadian Grain Commission's Grain Research Laboratory
has established official procedures for testing the moisture content
of wheat. In these procedures, moisture tests are always performed
on samples that have had dockage removed.
GRADES OF RED WINTER
WHEAT
The Canadian Grain Commission publishes an Official Grain Grading Guide that lists the commercial class of wheat, the official grades for each class, and the tolerance of the grade determinants of each class. The official grading standards and definitions for grading up to the point that wheat arrives at a terminal elevator are outlined in the Grain Grading Handbook for Western Canada. The Grain Grading Handbook is amended annually and both the Handbook and the annual amendments may be obtained from:
The Canadian Grain Commission publishes an Official Grain Grading Guide that lists the commercial class of wheat, the official grades for each class, and the tolerance of the grade determinants of each class. The official grading standards and definitions for grading up to the point that wheat arrives at a terminal elevator are outlined in the Grain Grading Handbook for Western Canada. The Grain Grading Handbook is amended annually and both the Handbook and the annual amendments may be obtained from:
Canadian Grain Commission
B-10-303 Main Street
Winnipeg, Manitoba
R3C 3G8
Tel. (204) 983-2975
The information presented in the following tables
describes the grades of red winter wheat effective August 1, 1995.
The No. 3 CWRW grade was eliminated and a premium for red winter
wheat with a protein concentration of 11.5 percent or higher was
initiated at that time.
Standard of Quality Maximum Limits
Grade Name
Minimum Test Weight (Kilograms per Hecto-litre)
Variety
Minimum % Hard Vitreous Kernels
Degree of SoundnessForeign Material Wheats of Other Classes or Varieties
Matter Other Than Cereal Grains
Total(Including Cereal Grains)
Contrasting ClassesTotal (Including Contrasting Classes)
No. 1 Canada Western Red Winter 78.0 Any variety of red winter wheat equal to acceptable reference varieties 50.0% Reasonably well matured, reasonably free from damaged kernels About 0.2% 1.0% 1.0% 3.0% No. 2 Canada Western Red Winter 74.0 Any variety of red winter wheat equal to acceptable reference varieties 35.0% Fairly well matured, reasonably free from severely damaged kernels About 0.3% 2.0% 2.0% 6.0% No. 3 Canada Western Red Winter 69.0 Any variety of red winter wheat equal to acceptable reference varieties No Mini-mum May be frost damaged, immature or weathered, but moderately free from severely damaged kernels About 0.5% 3.0% 3.0% 10.0% Canada Western Feed 65.0 Any type of variety of wheat except amber durum No Mini-mum Excluded from other grades of wheat on account of light-weight or damaged kernels, but shall be reasonably sweet 1.0% 10.0% No Limit (but not more than 10.0% amber durum) Less than 65.0 kg/hL: grade Wheat, Sample C.W., Account Lightweight Over 1.0%: grade Wheat, Sample C.W., Account Admixture Over 10.0%: grade Mixed Grain, C.W., Wheat Over 10.0% amber durum; grade Wheat, Sample C.W., Account Admixture
Smudge Insect Damage
Grade Name
Sprouted
Penetrated
Total SmudgeTotal Smudge and Blackpoint
Degermed
Grass Green
Pink
Sawfly, Midge
Grasshopper, Army Worm
Dark ImmatureNo. 1 C.W. Red Winter 0.5% 3K 30K 10.0% 4.0% 0.75% 3.0% 2.0% 1.0% 1.0% No. 2 C.W. Red Winter 2.5% 0.5% 1.0% 15.0% 7.0% 2.0% 6.0% 8.0% 3.0% 2.5% No. 3 C.W. Red Winter 8.0% 1.0% 3.0% 35.0% 10.0% 4.0% 10.0% 15.0% 5.0% 10.0% Canada Western Feed
No Limit No Limit No Limit No Limit No Limit No Limit No Limit No Limit
Grade Name
Natural Stain
Artificial Stain, No ResidueBinburnt, Severely Mildewed, Rotten, Mouldy
Total Heated (Including Binburnt)
Fireburnt
Stones
Ergot
SclerotiaShrunken and Broken
Shrunken
Broken
TotalNo. 1 C.W. Red Winter 0.5% Nil 2K 0.10% Nil 3K 3K 3K 6.0% 6.0% 7.0% No. 2 C.W. Red Winter 2.0% 3K 4K 0.25% Nil 3K 6K 6K 10.0% 10.0% 11.0% No. 3 C.W. Red Winter 5.0% 7K 6K 0.75% Nil 3K 12K 12K 12.0% 10.0% 13.0% Canada Western Feed No Limit 2.0% 10.0% 2.0% 10K 0.25% 0.25% No Limit 50.0% 50.0% Broken Over 2.0%: grade Wheat, Sample C.W., Account Stained Kernels Over 10.0%: grade Wheat, Sample C.W., Account Heated or Predominant Reason Over 2.0%: grade Wheat, Sample C.W., Account Fireburnt Over grade tolerance up to 2.5%: grade Rejected (grade) Account Stones Over 0.25%: grade Wheat, Sample C.W., Account Ergot Over 0.25%: grade Wheat, Sample C.W., Account Admixture Over 50% broken kernels: grade Sample Broken Grain
Note : The letter "K" in
these tables refers to kernels or kernel-size pieces in 500 grams.
Common bunt (stinking smut):
A plant disease caused by smut fungi, characterized by masses of
black spores. Kernels affected by smut may or may not have an associated
odour. Samples having no distinct odour but containing smut balls
may be specially cleaned by aspiration to remove the smut balls.
Samples having no odour but which are tagged with smut spores are
considered naturally stained. Samples having a
smutty odour and/or which are heavily infected with smut are graded
Wheat, Sample C.W./ Canada, Account Odour.
a) Cereal grains - Rye, barley, triticale, oats,
and groats (kernel with the hull removed), including wild oat groats,
that remain after a sample has had dockage cleaned out.
b) Matter other than cereal grain - Inseparable
seeds such as cockle, ragweed, Tartarian buckwheat, vetch, and wild
oats, and non-cereal domestic grains such as corn, peas, buckwheat,
and lentils that remain after a sample has had dockage cleaned out.
Special cleaning:
Special cleaning refers to any cleaning of grain over and above
the usual dockage assessment procedures. The grade of a delivery
of grain may be improved by special cleaning provided all interested
parties are advised. Material that may be removed by special cleaning
includes foreign material, stones, bunt, and broken kernels. Material
that is removed from wheat by special cleaning is assessed as dockage.
Oats and flaxseed may be separated from wheat by special machine
cleaning and sold as oats or flaxseed when they make up greater
than 6 percent of the gross weight of a shipment.
Fusarium Head Blight
("tombstone kernels"): This disease is characterized by the presence
of kernels which appear lifeless, thin, and shrunken. The kernels
are also affected by a whitish or pinkish fibrous mould occurring
in the crease area, but sometimes found in the germ of the kernel
as well. The presence of the mould on individual kernels is confirmed
using a 10 power magnifier. Fusarium may produce mycotoxins such
as vomitoxin. Affected wheat may be unpalatable or toxic to animals
and is considered acceptable for human consumption only when virtually
free of mycotoxins.
Hard vitreous kernels (H.V.K.):
Whole, reasonably sound kernels that, even though moderately bleached,
show clear evidence of vitreousness, i.e., the natural translucent
coloring which is an externally visible sign of hardness. Vitreous
kernels of wheats of other classes that blend are included in the
percentage of H.V.K. for grade determination.
Non-vitreous kernels - Kernels having a starch spot
of any size (piebald); broken or otherwise damaged kernels, severely
bleached kernels and kernels of contrasting wheat classes are all
considered non-vitreous.
Distinctly heated kernels - This description includes
kernels with discoloration ranging from pale brown to very dark
brown, but excludes blackened kernels. Samples containing more than
10 percent heated kernels by weight or having a distinctly heated
odour are graded Wheat, Sample C.W., Canada, Account Heated.
Binburnt, rotted, severely mildewed and mouldy kernels
- These kernels are blackened, swollen and puffed because of severe
heating or exposure to high-moisture conditions. The discoloration
may extend throughout the kernel and kernels may feel spongy under
pressure. Samples containing more than 10 percent heated, distinctly
heated, binburnt, rotted, severely mildewed or mouldy kernels by
weight are graded Wheat, Sample C.W./ Canada, Account (predominant
reason).
Sawfly damage - This refers to kernels that are shrivelled or distorted.Midge damage - This refers to kernels that are distinctly shrunken and distorted. These kernels are characterized by a depression or caved-in side that is marked by a scarred pericarp. The pericarp is frequently ruptured, exposing the endosperm or embryo. Exposed embryos are considered to have "apparent" sprout damage except where there is clear evidence of germination. The tolerance for "apparent" sprout damage is doubled if the damage to the kernels has been caused by midge.Grasshopper or army worm damage - This refers to kernels that have been chewed, usually on the sides.
Odour: Samples that
have any type of unnatural or objectional odour other than that
of heated or fireburnt kernels are graded according to the basic
quality of the sample, the type and degree of odour, and the presence
of visible residue causing the odour. Samples having a distinct
objectionable odour not associated with the quality of the grain
are graded Wheat, Sample C.W./ Canada, Account Odour. Samples having
a heated odour are graded Wheat, Sample C.W./ Canada, Account Heated.
Samples having a fireburnt odour are graded Wheat, Sample C.W./Canada,
Account Fireburnt.
Shrunken and broken kernels:
Whole kernels that pass through the No. 4.5 slotted sieve are considered
shrunken. Pieces of kernels that are less than three-quarters of
a whole kernel are considered broken. Shrunken and broken kernels
consist of material passing through the No. 4.5 slotted sieve plus
any broken kernels remaining in the sample after sieving.
Smudge: This is
a discoloration or stain similar to blackpoint. The stain may be
brown, black or the reddish discoloration associated with some plant
diseases. Smudge is a grading factor when more than one-half of
the kernel is discolored or when the discoloration extends into
the crease of the kernel. As well, if less than one-half of the
surface is discolored but the infection extends into the crease,
the kernel is considered smudge-damaged.
Penetrated smudge - This discoloration penetrates
and extends throughout the endosperm and is usually caused by a
serious infection of fungal plant disease such as Alternaria.
Red smudge - This dark reddish discoloration is
most commonly associated with amber durum wheat and usually affects
the entire bran portion of the kernel. Discoloration is not superficial
and cannot be removed through abrasion. Red smudge is caused by
infections of the fungus Drechslera tritici-repentis, which is also
responsible for diseases such as tan-spot.
a) there is clear evidence of growth in the germ area,
b) the bran is noticeably split over the germ from apparent growth,
c) the germ is removed and there is apparent discoloration normally attributable to sprouting, or
d) the germ, though intact, appears distinctly swollen as a result of growth.
Kernels with slightly swollen germs or in which
the bran is split but there is no apparent sprouting are not considered
sprouted.
Stained kernels:
Artificial stain - Includes any stain on kernels caused by contact
with foreign substances such as dye, or adhered foreign material
such as oil, grease, paint, or soot, but excludes any stain caused
by poisonous substances.
Natural stain - Includes any stain on kernels caused by contact with natural substances such as smut spores, soil or weeds.
Streak mould: Samples containing kernels with unusual dark grey streaks on their sides toward the brush may be affected by streak mould. This very slow-growing mould is harmless in wheat, except that it affects kernel appearance. It occurs most commonly in red winter wheat. It is not related to the more serious storage moulds. Streak mould is included with blackpoint for grading purposes.
Natural stain - Includes any stain on kernels caused by contact with natural substances such as smut spores, soil or weeds.
Streak mould: Samples containing kernels with unusual dark grey streaks on their sides toward the brush may be affected by streak mould. This very slow-growing mould is harmless in wheat, except that it affects kernel appearance. It occurs most commonly in red winter wheat. It is not related to the more serious storage moulds. Streak mould is included with blackpoint for grading purposes.
D. Brian Fowler
Crop Development Centre
University of Saskatchewan, Saskatoon, Canada.
Copyright © 2002. D.Brian Fowler
All Rights Reserved.
Revised
URL:http://www.usask.ca/agriculture/cropsci/winter_cereals/
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