P-24
A new method to assess mealiness and steeliness of barley samples. Endosperm structure influences the malting quality of barley. Mealy endosperm
tends to have loose-packing of protein and starch granules, providing large
"water-free spaces", which accelerate water uptake and facilitate enzyme
distribution and enzyme hydrolysis (modification) of the endosperm during
malting. In contrast, steely endosperm is characterised by compaction of
starch-protein materials, which are less hydrated and resist enzyme hydrolysis during
malting. The degree of mealiness and steeliness of a sample depends on the
endosperm structure, which is affected by genetics, field and climate
conditions, and pesticide and insecticide application. The cold sulphuric acid
(50%) method was applied to dehusk different barley varieties. Visual inspection
was used to separate dehusked barley grains into mealy or steely grains, or
grains with intermediate structure. However, visual inspection cannot detect the
degree of mealiness and steeliness of barley samples because, for example,
surface mealiness may obscure underlying steeliness of individual grains.
Mindful of this, a new method was developed to assess the degree of mealiness
and steeliness of dehusked and normal barley samples. The method is based on
measuring the turbidity of milled barley fractions in 70% cold ethanol. Mealy
endosperm structures released more starch granules into cold ethanol. This was
measured using a turbidity meter. The resistance of each sample to milling
influences the turbidity value and differentiates mealiness from steeliness.
Turbidity values were found to correlate with the endosperm structure observed
using the Scanning Electron Microscope (SEM). Barley endosperms with different
degrees of compaction gave different turbidity values. Those with large starch
granules and loose structure gave higher turbidity values than those with
smaller granules and compact endosperm structure. Correlations between turbidity
values and malting parameters, such as wort beta-glucans, were also observed.
This suggests that turbidity assessment could be used as a predictive test of
malting quality.
Maria Koliatsou received her first degree in Enology and Beverage
Technology from Athens University (Technological Educational Institute) in
Greece. She was then awarded a scholarship from the State Scholarships
Foundation in Greece, to study in Scotland. She received an MSc in Brewing and
Distilling from the International Centre for Brewing and Distilling at
Heriot-Watt University. She is currently studying for a Ph.D. degree in Cereal Science
under the supervision of Professor Geoff Palmer. Her work focuses on the
influence of endosperm structure to the malting quality.
MARIA KOLIATSOU and Geoff H. Palmer. The International Centre for Brewing and
Distilling, Department of Biological Sciences, Heriot-Watt University,
Edinburgh, Scotland, UK.