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Prairie wheat mildew report

Mildew led to widespread downgrading in 2014, but the crop’s overall quality outlook is still positive

This past fall, mildew has been one of a number of downgrading factors affecting the Prairie wheat harvest to a greater extent than last year, but it doesn’t necessarily mean it’s all bad news for finding markets for milling quality wheat.

Each fall Cigi (Canadian International Grains Institute) receives samples of the different wheat classes from grain companies which are then made into composite samples and evaluated for quality characteristics in end-use products, with the results then presented to industry and customers around the world.

As well, the Canadian Grain Commission (CGC) prepares standard samples representing the typical condition of each wheat class for grading by CGC grain inspectors. The samples represent grading factors (including mildew, frost/heat stress, and green or immature wheat) that are influenced by environmental growing conditions and are assessed visually (for more information visit grainscanada.gc.ca).

Across the Prairies in 2014, the higher incidence of mildew, caused by the fungus Cladosporium, is attributed to wet conditions at harvest, says Elaine Sopiwnyk, director of science and innovation at Cigi.

“Parts of Alberta received snow that resulted in some lodging of the grain where stalks fall over and get compacted by moisture that promotes spore growth,” Sopiwnyk reports. “As of early October, mildew accounted for almost 65 per cent of the downgrading of CWRS to No. 3, with even more in Manitoba but less in Saskatchewan. Other downgrading factors that seem high this year are frost/heat stress, sprout damage, and fusarium which is especially high in Manitoba and Saskatchewan.”

Mildew is non-toxic and causes a discolouration of wheat flour, Sopiwnyk says. The greyish colour can be undesirable in some end-products that require a high level of brightness or whiteness, such as for white pan breads or for some Asian products like steamed breads. “Some of these markets are really discriminating, and the brightness and whiteness of their product is very critical. CWRS, for example, is exported to so many markets with different end-product applications and quality requirements.”

In addition, Sopiwnyk points out that sometimes the wet conditions causing mildew may also cause additional degrading factors due to weathering that can affect flour and end-product quality. “Generally, mildew is an indication of the weathering that occurred. If you have grain that is wet at harvest, then there is also a possibility of sprout damage as well.”

Ashok Sarkar, Cigi senior adviser for technology, agrees that more than one degrading issue can be associated with a wet harvest. And while mildew dulls the colour of flour, the inclusion of some blackened parts of the wheat kernel in lower grades of durum wheat during milling can also add undesirable dark specks to durum semolina which could affect the appearance of pasta.

However, Sarkar says some markets that are more sensitive to price than quality are open to using wheat affected by mildew for blending with other flour for baked goods. “Even domestically there are baked products where mildew does not have an impact on quality,” Sarkar says. “But in places like Asia where noodles and steamed bread require a bright and white colour, wheat with high levels of mildew may not be acceptable.”

Sarkar says that a bleaching agent can be used during milling to whiten dull flour, but with only limited effect. “It’s all relative,” he says. “Mildew strictly affects colour while, on the other hand, I’d say something like frost damage is one of the more difficult grading factors to deal with from a milling and end-product quality standpoint.”

This year initial reports have indicated that mildew is not having too detrimental an effect on flour or crumb colour, Sarkar adds.

Cigi began presenting its harvest assessment to customers mid-fall and, together with the CGC and Cereals Canada, it will hold new crop seminars in Asia, Europe, South America, the Middle East, and North Africa.

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