Inspecting grain for defects and impurities

Broken grains

Exposed endosperm, usually due to aggressive handling, provides potential sites for mould infections.

For milling, broken grains are removed during the cleaning process. However, this results in a lower yield of clean, white flour from each tonne purchased.

For malting, broken grains cause processing issues. These include excessive water uptake and mushy steep, with starch leaching into steep water.

Sprouted grains (wheat)

Germinated grains, caused by wet harvest conditions, have very high levels of alpha-amylase. Even a few in a bulk can reduce Hagberg Falling Number to unacceptable values, resulting in rejection of milling wheat.

Pre-germination (barley)

As pre-germinated grains may not malt, they can reduce malt yield. Such grains can be detected in laboratory tests.

A swollen and raised germ area is a sign of light pre-germination (top image). Visible rootlets are a sign of heavy pre-germination (bottom image).

Gape (barley)

Influenced by the variety and the environment, gape is a gap between husk tissues (lemma and palea). It occurs due to poor development and/or excessive expansion. The endosperm remains intact and it not necessarily considered a defect, unless lateral splitting occurs.

Splitting (barley)

Cracks through outer grain tissues may arise from excessive expansion or mechanical weakness. Splits often occur along the ventral crease but can also occur on the side (lateral) and back (dorsal). Exposed endosperm is susceptible to mould attack. Processing problems include excessive water uptake and mushy steep, with starch leaching into steep water.

Skinning (barley)

A separation and loss of lemma and palea (husk). Causes include developmental factors, weather conditions, rough harvest and post-harvest handling. May lead to filtration problems due to loss of husk and hence malt production efficiency is likely to be reduced. Dust problems during handling may arise. More prevalent in spring varieties.

Lost embryos

Embryos may be damaged mechanically or by mites (as shown) or insects. Damage by mites or insects may indicate poor storage. Such grain is no use in malting, as the grain will not germinate.

Burned/heat-damaged grains

Heat damage arises from localised ‘hot spots’ or excessive temperatures during drying. Grains can range in colour from bronze to dark brown (charred). Such wheat is unacceptable. Over-dried grain will have irreversibly damaged gluten. For barley, over-dried grains are unlikely to germinate and may affect beer or malt flavour.

Unwanted non-cereal matter (e.g. chaff, straw, stones) that has no value to the miller and must be removed before milling. Stones can damage machinery; metal objects may cause sparks.

Large screenings

Includes straw, beans, unthreshed grain, sticks and stones.

Small screenings

Includes broken grains, shrivelled grains, chaff, weed seeds and small straw pieces.

Mud and stones

Mud balls are a particular problem during wet harvests. Stones can be picked up during combining, particularly when harvesting conditions are difficult.

Dust, chaff and fine soil

Do not smell grain dust, as it can be harmful if inhaled and cause respiratory problems.

Blackpoint

In response to infection, the plant produces chemicals in the bran and the germ area can become brown to black. Dark bran specks in flour affect quality. Blackpoint is often associated with Alternaria infection, but this is not the only cause. Some varieties are more prone to blackpoint than others.

Bunt

Bunt infection can result in fragile, dark-coloured grains. Part of the grain may have eroded. Surface cracks may reveal black powdery spores within the endosperm. Bunt balls occur occasionally and spores give grains a dull look. Infected grain has a pungent fishy smell, making it unacceptable for cereal products.

Ergot

The fruiting body of the fungus Claviceps purpurea affects grasses as well as rye, wheat and barley. The inside of an ergot is grey/white, which distinguishes it from rodent droppings. As ergot is toxic to humans and animals, it is unnacceptable to any processor.

Fusarium

Pink moulds indicate possible Fusarium infection. Some Fusarium fungi can produce mycotoxins that are toxic to humans and animals. Permitted mycotoxin levels are governed by legislation or trading specifications.

Infection may cause gushing of bottled beers.

Mould

Dull looking, weathered grains indicate poor harvest conditions and may impair quality, eg wholemeal colour. Dullness may be due to spores or moulds which are unacceptable to all users due to the risk of mycotoxin formation.

Spores present possible health hazards and must not be inhaled.

Insects and mites are a sign of suboptimal storage conditions. The presence of live insect pests is unacceptable to processors.

To check for insects, sieve representative samples (typically using a 2mm mesh) and inspect the material thoroughly. This is especially important for grain going into storage.

General insect damage

This example shows weevil damage. Eggs are laid within the grain. Endosperm is eaten by the larvae inside the kernels. 

Orange wheat blossom midge

Midges infest crops at flowering, laying eggs in empty florets. The larvae attack immature grain, pierce the bran and inject enzymes into the grain. This can lead to water ingress and low Hagberg Falling Numbers. Black areas indicate additional fungal infection.

Rodent dropings

Rodents directly damage grain and carry infection. Rodents urinate on grain, posing a food safety risk. Contaminated grain is unacceptable.

Mould

Dull looking, weathered grains indicate poor harvest conditions and may impair quality (e.g. wholemeal colour). Dullness may be due to spores or moulds which are unacceptable to all users due to the risk of mycotoxin formation.

Spores present possible health hazards and must not be inhaled.

25mm

6mm

7–14mm

20–30mm

3–4.5mm

2–5mm

2–3.5mm