Downgrading Factors Prevalent in the 2019 Harvest

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Environmental conditions during the 2019 crop year will affect wheat quality by causing downgrading. Some of these downgrading factors may include, but are not limited to, Immature, Green, Frost/Heat Stress, Mildew and Sprouted kernels. Official definitions of these factors, how they are assessed and the limits for each class/grade can be found in the Canadian Grain Commission’s Official Grain Grading Guide (OGGG)[1]. Quality impacts of these factors are explained in this document.


Green (GR)

Definition: Green wheat kernels result when the maturation process has been affected or arrested by the environment (e.g. frost) or an agronomic practice which results in kernels which may vary in colour, size and shape.

Quality Impact: Kernels with a distorted appearance can affect milling performance and result in reduced flour extraction and flour with higher ash content (undesirable) and poor flour colour compared to sound kernels. This would also negatively affect the colour of the end-product (bread, noodles, pasta).


Immature (IM)

Definition: Immature kernels result when kernel development has been halted. This often results in kernels that will have variations in colour, size and shape from a sound kernel.

Quality Impact: Flour milled from kernels that are downgraded on account of IM may show reduced flour extraction, increased flour ash (undesirable) and poor flour colour (undesirable). End-product (bread, noodles, pasta) colour would also be negatively affected.


Frost/Heat stress (FRHTS)

Definition:  The bran of wheat that has been exposed to freezing temperatures or prolonged hot weather conditions will become blistered, the extent of this is dependent on the maturity of the grain, the temperature and duration of exposure.

Quality Impact: Kernels impacted by FRHTS are harder in texture which can affect milling performance and reduce flour extraction levels. The flour may also have higher levels of starch damage which may impact flour water absorption and negatively affect water retention during fermentation (undesirable/sticky doughs that are difficult to process). The bran also become more brittle which can result in more bran in the flour and therefore higher flour ash content (undesirable) and poor flour and end-product colour.


Sprouted kernels (SPTD)

Definition:  Sprouting occurs when kernels, which are near maturity, receive moisture (rain or heavy dew) which signals the kernel to begin the process of germination. Sprouted kernels may have a swollen germ area, the bran may be split over the germ, there may be evidence of growth in the germ area or the germ may be missing. Sprouted kernels may also be discoloured on account of weathering.

Quality Impact: Alpha-amylase is an enzyme which affects the starch in the kernel. In sprouted kernels alpha-amylase is present in high levels and will cause low falling number and low amylograph peak viscosity values, both of which are undesirable. Bread made from flour milled from wheat that is sprouted can have poor dough handling properties during the bread making process, reduced loaf volume and poor crumb structure and colour. Flour produced from wheat with high levels of sprout damage may also impact the colour of the noodles.


Mildew (MIL)

Definition:  Mildew occurs when there are high moisture levels and results in kernels that will appear grey in colour particularly on the brush end of the kernel. However, mildew can also extend into the crease of the kernel.

Quality Impact: Mildew negatively affects flour colour, making it dull and dark, which consequently also impacts end-product colour (bread, noodles, pasta). Flour milled from sound kernels would have a bright, white appearance.


Hard Vitreous Kernels (HVK)

Definition: Vitreousness is the natural translucence, or glassy appearance of a kernel that provides an indication of kernel hardness. HVK is a grading factor for CWRS and CWAD.

Quality Impact: In CWAD, HVK has a positive relationship with semolina extraction, therefore high HVK levels are desirable, especially if there is a need to produce coarse semolina. In common wheat, HVK has an impact on milling quality, but to a lesser degree than in CWAD, and this is the reason why there is a minimum requirement for HVK for No. 1 CWRS.


For more information, please contact:

Elaine Sopiwnyk
Director of Grain Quality
esopiwnyk@cigi.ca
(204) 983-2163


[1] https://www.grainscanada.gc.ca/en/grain-quality/official-grain-grading-guide/04-wheat/grading-factors.html