Skinned malting barley grains are not a new phenomenon, according to Teagasc’s Ciaran Collins, as they have always been present.
“We have spoken a lot about skinning in the last 12 months and I nearly have to think to myself did skinning just start to occur last year or the year before.
“We have always had skinning,” he said, and it has been happening for a long time, but the difference now is the implications it has for the malting industry.
Collins, a tillage advisor based in Fermoy, spoke at the recent Teagasc Malting Barley Seminar where he presented work on skinning from the SRUC in Scotland.
What is grain skinning?
Skinning occurs when the husk becomes detached from the underlying endosperm leading to irregular germination during malting, he said.
“This makes water uptake and the conversion of starch into sugars more variable and it is that variability that the maltsters say is the biggest issue.
“In the worst case scenario you could have a grain with no husk at all and it may not even germinate.
Skinning leads to the loss of malting efficiency, variety failure is a big cost breeders and rejection at malting is obviously a big loss to farmers after the investment that has been made in growing the crop.
What causes skinned grains?
Collins also discussed a number of factors that have been show to increase the presence of skinned grains in a harvested malting barley crop.
Citing work carried out by Dr Marie Brennan, Collins said the weather has an impact on the level of skinning seen in malting barley grains.
He said that high humidity and low sunlight levels 19 days after flowering can affect the process of adhesion, while wetting and drying of the mature grain can also have a negative impact on the adhesion of the husk to the grain.
New malting barley varieties, he said, are also more susceptible to skinning but there are seasonal variations as well.
Looking at UK data, Collins said that modern varieties tend to have a weaker husk adhesion and as a result they are more prone to skinning.
The Teagasc representative also cited trial work which showed that the proportion of skinned grains increases as the nitrogen fertiliser level is increased from 120kg/ha to 150kg/ha.
Generally you get a higher percentage of skinned grains as the Nitrogen levels increases, but it’s not black and which as site location may have a role to play
On the issue of sowing date, Collins said earlier sown crops tend to have lower skinning percentages than crops sown and harvested later.
“Late harvested crops tend to have increased levels of skinning.”
Moving to the combine, Collins said research work has shown that the skinning increases, both in susceptible and resistant varieties, when the drum speed is increased.
“At 1,000RPM you are looking at a range of 8-12% skinning for resistant grain varieties and 20-30% in susceptiable varieties
“In both cases as the drum speed increases the percentage of skinning increases irregardless of whether the variety is resistant or susceptible.”
He added that a similar pattern is also seen when it comes to concave settings on the combine.