Future Trends in Grading and Classification of Canadian Wheat

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.