Backgrounder: Research summary for mildew standard samples

The Canadian Grain Commission’s Grain Research Laboratory conducted extensive research from 2020 to 2022 to better understand the relationship between mildew damage and the end-use qualities of Canada Western Red Spring (CWRS) wheat. This new research followed a similar investigation completed from 2014 to 2016.

Mildew damage on wheat kernels appears as a grayish to black discolouration and is caused by fungi that develop due to excessive moisture prior to harvest. Mildew is generally not considered a toxicological hazard, but it can affect the end-use quality of wheat. Kernels affected by mildew are graded using standard samples that visually correspond to different degrees of soundness.

Overall, we found the following in our research:

• flour milling yield: little to no impact on most grades and slightly lower yields for samples graded as Feed
• flour refinement: minor impact, including for ash, brightness, and specks
• gluten strength and baking quality: little impact on dough viscoelasticity and loaf volume
• hard vitreous kernels (HVK): low for samples graded No. 3 or Feed
• farinograph water absorption: slightly lower for samples graded as Feed

The Canadian Grain Commission research team found that mildew was usually concurrent with sprouting. When wheat begins to sprout, it produces an enzyme called alpha-amylase, which can degrade starch in the dough and reduce wheat quality. As a result:

• a higher degree of mildew is generally associated with higher alpha-amylase activity, which attributes to lower Falling Number and amylograph peak viscosity.
• mildew can be a useful indicator of elevated alpha-amylase activity before sprouting becomes visible
• keeping mildew as a grading factor can provide additional quality protection supplementary to sprout tolerances