Sprout damage (SPTD) and severe sprout damage (SEVSPTD)

Sprout damage

Sprout damage in most wheat classes is subdivided into sprouted and severely sprouted. The amount of the enzyme alpha-amylase in severely sprouted kernels can be many thousands of times greater than the amount found in sprouted kernels. Sprout damage (the onset of germination) is an objective grading factor.

All classes of western Canadian wheat are assessed for sprouted and severely sprouted kernels. All classes of eastern Canadian wheat are assessed for sprouted kernels.

The tolerances for sprouted and severely sprouted kernels are listed in Chapter 4 of the Official Grain Grading Guide.

Photograph of sprout damage on kernels of CWRS wheat.

Sprout damage on kernels of Wheat, Canada Western Red Spring.

Photograph of a single kernel of sprouted wheat.

This kernel is considered sprouted. It is not considered severely sprouted because the sprout just meets the contour of the germ.

Photograph of two severely sprouted kernels.

These kernels are considered severely sprouted, because the sprout extends beyond the contour of the germ.

Photograph of six severely sprouted kernels

These kernels would be considered severely sprouted: The kernels show broken coleoptiles (sprouts) that were once extending beyond the normal contours of the germ.

Definition of sprout damage (SPTD)

Kernels are sprouted if one of the following conditions exist, as shown in these kernels of Canada Western Red Spring wheat.

A pale yellow area appears in the germ area of the kernel.The kernel is sound and does not show signs of sprout

Left: An example of a sprout damaged kernel. There is evidence of growth in the germ area of the kernel.

Right: The kernel is sound.

The bran is split.The kernel is sound and does not show signs of sprout damage.

Left: An example of a sprout damaged kernel. The bran over the germ is split by apparent growth.

Right: The kernel is sound.

The kernel is discoloured. The kernel appears shriveled and the bran is split.The kernel is sound and does not show signs of sprout damage.

Left: An example of a sprout damaged kernel. The germ is intact, but it is swollen because of sprouting activity.

Right: The kernel is sound.

Definition of severe sprout damage (SEVSPTD)

Kernels are assessed as severely sprouted when:

The sprouts extend beyond the normal contour of the germ

The sprouts extend beyond the normal contour of the germ

The kernels are severely degenerated as an apparent result of advanced sprouting

The kernels are severely degenerated as an apparent result of advanced sprouting

The sprout has been clearly broken and only a portion remains

The sprout has been clearly broken and only a portion remains

The sprout is completely gone

The sprout is completely gone and there is evidence showing that there was extension of the sprout outside the normal contour of the germ

Causes of sprout damage

Sprout damage is pre-harvest germination. Under conditions of prolonged dampness or rain, wheat kernels may start to germinate while the wheat crop is lying in the swath. This may also occur in lodged stands or, under very warm and wet conditions, when the mature crop is still standing. Germination begins when mature kernels absorb water and generate enzymes that break down stored starch and protein in the endosperm. The enzymes release sugars from starch and amino acids from proteins which nourish the growing embryo. One of these enzymes is called alpha-amylase.

Alpha-amylase

Some alpha-amylase enzyme is present in the embryo or germ of sound wheat kernels. When germination begins, however, the embryo and layers surrounding the starchy endosperm produce it at an accelerating rate. A severely sprout-damaged kernel contains many thousands of times the amounts of enzyme present in kernels that are in the early stages of germination. Because of this, a wheat sample containing very low levels of severely sprouted kernels may exhibit significant amylase activity. Alpha-amylase converts starch into sugars in the sprouting kernel, and similarly breaks down the starch granules in wheat flour when mixed with water to make bread dough.

Falling number is the internationally accepted measure of alpha-amylase activity.

Alpha-amylase affect on bread-making quality

Flour damaged by alpha-amylase holds less water when mixed and the dough absorbs less water during baking. The baker must use more flour to make the same number of loaves of bread, an important cost factor.

The enzyme also affects gas retention, dough handling and bread texture. Too much alpha-amylase activity causes wet, sticky dough that is hard to handle in a commercial bakery. The loaf may have large, open holes and the crumb texture is gummy. Gummy bread is difficult to slice and builds up on slicer blades. Loaves are often deformed, hard to package and unattractive to customers.

Loaves of bread made from Wheat, Canada Western Red Spring

Three loaves of bread made from Canada Western Red Spring wheat illustrate how different levels of sprout damage affect bread-making quality.

The loaf made from sprouted wheat is sticky. When it is sliced, it shreds. The problem is exacerbated with the loaf made from severely sprouted wheat.

3 loaves of wheat bread made with sound (left), sprouted (centre), severely sprouted (right)

Left: Loaf made from sound wheat.

Middle: Loaf made from sprouted wheat is sticky and shredded when sliced.

Right: Loaf made from severely sprouted wheat is stickier and more damaged when sliced.

Alpha-amylase affect on pasta-making quality

Sprouting in durum wheat produces the enzyme alpha-amylase, which causes lower falling numbers. The enzyme does not affect durum quality as seriously as it affects red spring wheat quality, but is still a concern to some millers and pasta manufacturers, especially in the United States. American millers and pasta manufacturers typically want durum wheat or semolina with very little sprout damage and high falling numbers. The American market is an important market for Canadian durum wheat.

Lower falling number, caused by high levels of sprout damage, has an influence on cooked pasta. The texture gets softer and the more starch is lost to cooking water, making the water cloudy. Many pasta processors say high levels of sprout damage cause production problems such as uneven extrusion, strand stretching, and irregularities in drying, that is, checking or cracking of strands during storage.

The last effect, but probably the most unpleasant to consumers and food services, is that the pasta cannot withstand overcooking and becomes soft or mushy. Most people like their pasta with a bit of bite or al dente.

All of these effects increase with higher percentages of sprout damage.

Sprout damage in durum wheat has little impact on milling quality, but is often associated with mildew damage. This can lead to black specks and duller colour in semolina and pasta, instead of the usual bright yellow.

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