Sprout damage (SPTD) and severe sprout damage (SEVSPTD)
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.
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.
Definition of severe sprout damage (SEVSPTD)
Kernels are assessed as severely sprouted when:
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.
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.
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.
- Tolerances for sprouted and severely sprouted kernels for wheat
- Analytical testing for sprout damage
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