1. More Objective Grading
The visual grading system used by the CGC is fast and efficient, but
it is often criticized for being too subjective. In response to this criticism
the CGC is evaluating rapid objective test procedures in support of grading,
and investigating whether there is an alternative to using standard samples to
estimate the degree of soundness.
Rapid objective test procedures being evaluated by the CGC include
near-infrared spectroscopy (NIRS), image analysis (also referred to as machine
vision) and RapidViscoTM Analyzer (RVA). NIRS is well established for
estimating wheat protein content and moisture content in Canada (Williams et
al., 1978). Pawlinsky and Williams (1998) reported that NIRS has potential to
predict bread-making functionality as well as wheat composition, but this has
yet to be conclusively demonstrated. Preliminary investigations indicate that
NIRS might be able to estimate durum wheat HVK levels accurately and reliably
(Dexter et al., 2002).
Machine vision has been touted by many as an effective objective
support to visual grading. Machine vision classifies kernels on the basis of
size, shape and texture. Symons et al. (2003) described a CGC machine vision system
that classifies individual durum wheat kernels according to degree of vitreousness,
which allows a percentage HVK to be computed. The instrument has yet to be evaluated
in a grain handling environment. Machine vision grading instruments are becoming
commercially available for grading wheat and other commodities. Nutech Analytical
(formerly Maztech MicroVision) have introduced the SPY Grain Grader (www.nutechanalytical.com) which has various applications, including identifying Fusarium damage in red
wheat, and diseased and discoloured kernels in durum wheat. Under the name
AcurumTM (www.acurum.com), Dupont Canada is
promoting a machine vision system developed by Agriculture and
Agri-Food Canada that reportedly can classify and measure the degree
of damage to individual wheat kernels and other grains, pulses and oilseeds.
RVA is being evaluated by the CGC as a rapid test to segregate
sprouted wheat from sound wheat according to activity of the enzyme α-amylase.
Sprout damage is a serious grading factor because sprouted kernels contain high
levels of α-amylase, which can seriously harm bread-making quality (Dexter and Edwards,
1998a). The Falling Number (FN) is internationally recognized as the best
objective measurement of α-amylase activity in wheat, but the test cannot be
performed within the time constraints for making binning decisions in a high-throughput
grain receiving facility. Visual estimation of sprout damage is a rapid and
useful management tool for protecting bulked wheat from excessive levels of α- amylase,
but it is unable to predict α-amylase accurately in individual lots of wheat.
RVA stirring number relates strongly to FN, and RVA is a more rapid test than
FN. Pre-harvest sprouting was a major grading factor for the 2002 western Canadian
wheat harvest. RVA was used successfully by the CGC following the 2002 harvest
to efficiently segregate individual wheat lots arriving at grain terminals by
degree of sprout damage (CGC and CWB, 2002).
As described earlier, standard samples are prepared by the CGC every
autumn, following the harvest, as visual aids to accessing the degree of
soundness. Standard samples have proved effective in rapidly assessing degree
of frost, mildew damage and immaturity. However, preparation of standard
samples is labour-intensive, and getting them to grain grading locations
promptly after the harvest is a challenge. Research is currently underway to
determine whether numerical tolerances for mildewed, frosted and immature kernels
can be established that simulate soundness limits similarly to standard
samples, without increasing the time needed to assign a grade.
2. Alternatives to KVD
KVD has been used by Canada successfully for many years to keep wheat
classes separate. As discussed previously, KVD works because Canada has a strict
variety registration system that requires that varieties conform to the prescribed
kernel features for its class. But KVD is a limitation to developing improved varieties.
KVD is under pressure due to proliferation of wheat classes in western
Canada, and increasing demand for varieties with specific quality attributes
for niche markets. For example, AC Navigator extra-strong gluten durum wheat is
indistinguishable from conventional strength CWAD varieties, CWHW wheat
varieties are indistinguishable from soft white spring wheat, and soft white
spring wheat varieties with specific starch pasting properties cannot be
distinguished. At the time this article was written (2004), no genetically
modified (GM) wheat varieties were registered in Canada, but there may be applications
for registration of GM cultivars that are indistinguishable from non-GM wheat
within a few years.
Accordingly, development of rapid variety identification methods to
facilitate and monitor purity of variety-specific segregation is a major
research emphasis in Canada. Separation of wheat storage protein by electrophoresis
(Tkachuk and Mellish, 1980) and reversed-phase high performance liquid chromatography
(Marchylo et al., 1988) are well established and effective methods of determining
variety composition at the CGC, but they are too costly, slow and complex to be
used in a high-throughput grain handling facility.
DNA fingerprinting is under investigation by the CGC for variety
identification (CGC and CWB, 2000). Regions of DNA are analyzed to identify
differences in DNA coding sequences that uniquely distinguish one variety from another.
These sequences can then be used as probes to identify the DNA of varieties commingled
in grain shipments. The goal of the CGC is to provide Canada with rapid, automated,
portable and cost effective DNA fingerprinting technology to support identity
preservation systems, and to allow certification of shipments for a desired
variety or varieties.
In 2001 the CGC formed an advisory committee, including
representatives from producer groups, grain companies and marketers to review
KVD. A rapid variety identification test to replace KVD is still years away.
They therefore recommended a variety eligibility declaration (VED) system.
Under VED, every time wheat changes hands there would be a declaration that the
lot is comprised of a variety or varieties eligible for a specific class. Documentation
and sampling would make it possible to trace grain in a cargo right back to
elevators and farmers who made deliveries, allowing monitoring and enforcing
accountability, thereby assuring the quality of wheat shipments.
In 2003 the CGC conducted broad consultation on VED with all
stakeholders in the Canadian grain industry. There was widespread agreement that
an effective alternative to KVD would be desirable, but concerns were raised
about accountability and liability, logistics and benefits versus costs. In
response to these concerns, a committee of producers and industry representatives
was charged by the CGC to address logistical issues, and the CGC initiated a
cost-benefit analysis. In December 2003 the CGC announced that mandatory VED
would not be implemented because cost outweighed benefit. However, the CGC
acknowledged that it was likely that variety declarations will increasingly be
used in private, commercial transactions, and that eventually variety declarations
will form an integral part of the Canadian grain production, marketing and
handling system.
In the interim, the CGC has proposed a wheat quality assurance
strategy with three elements:
• development of rapid, affordable variety identification technology;
• increased CGC monitoring of rail and vessel shipments for
nonregistered varieties, and downgrading shipments if they contain nonregistered
varieties in excess of grade tolerances;
• development of a proposal to restructure the western Canadian wheat
classes to enable the development, registration and handling of non-milling
wheats, such as high yielding feed varieties.
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