Study on mildew visual guides and standards for western Canadian milling wheat grades
Backgrounder
The Canadian Grain Commission continuously reviews grade standards on all classes of wheat to ensure that grade standards are effective, based on objective scientific testing, in discriminating the key quality requirements of the class. In September 2014, the Canadian Grain Commission noted that numerous samples of wheat from the Canada Western Red Spring class collected as part of the annual Harvest Sample Program were displaying increased amounts of mildew damage and were being downgraded. Recognizing the large economic impact that this was having on Canadian farmers and anticipating their concern, the Canadian Grain Commission initiated a two-year study to ensure that the current mildew visual standards were appropriate.
Mildew kernels are kernels affected by field fungi that develop under conditions of excessive moisture and affect un-threshed kernels of wheat. Samples affected by mildew have grey to black mildew spores, typically attached to the brush end of the kernel. As the mildew increases, the greyish or black discoloration may extend onto the kernel and into the crease. Samples containing kernels affected by mildew are graded according to the degree of soundness definition as described in the Official Grain Grading Guide and the applicable standard and guide samples for each grade. The primary detrimental impact of mildew is reduced flour brightness.
During a two-year study of the 2014 and 2015 crop years wheat samples representing all grades were selected, graded and evaluated for mildew content by Canadian Grain Commission inspectors. To ensure that mildew was the only factor being evaluated, the wheat samples chosen were those that were downgraded solely due to mildew.
During the study, two genera of fungi were found using an advanced, DNA-based, polymerase chain reaction method. The major genus found was Alternaria with two species, alternata and infectoria, being present. A small amount of a second genus, Cladosporium, was also detected. A full-scale scientific study was initiated, involving assessment of falling number, wheat and flour protein, milling yield and water noodle dough colour at two and 24 hours. Additional standard quality tests such as flour ash, wet gluten, farinograph characteristics and extensograph parameters were also investigated. The findings of the study indicated that the current mildew guides needed to be adjusted to properly convey the intrinsic quality of the wheat and therefore increased presence of mildew.
Testing was also conducted on the impact of mildew on Canada Western Amber Durum Harvest Sample composites and Mildew Guides. Tests performed by the Grain Research Laboratory showed the impact of mildew on semolina quality was negligible.
The Canadian Grain Commission also consulted with milling experts at the Canadian International Grains Institute to ensure that adjusting the mildew guidelines will have no impact on products made from Canadian wheat. The Canadian Grain Commission met with the Western Standard Committee’s wheat sub-committee on October 3, 2016 and reviewed the results of the two-year scientific study. It was recommended by the wheat sub-committee that the mildew guides be adjusted in western milling wheat classes to allow for an increased presence of mildew in the visual standards.
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Contacts
Randy Dennis
Chief Grain Inspector for Canada
Canadian Grain Commission
204-983-2780
randy.dennis@grainscanada.gc.ca
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