A rapid test for malting quality in barley

Abstract

Grain milling energy (GME) was devised as a rapid test to identify genotypes with endosperm properties similar to Triumph. The rapidity of the test and the small sample size required make it suitable as a preliminary screen in a breeding programme. A study of the effects of environmental factors indicated that GME is not affected by variation in grain nitrogen as is hot water extract (HWE). While storage of grain samples can cause considerable changes in HWE, GME does not change.

GME can be dissected into a number of components which are related to the milling energy requirement of the major tissues. The husk and aleurone require more energy to mill than the starchy endosperm but, as they together form only some 15-20% of the total weight of the grain, 70% of GME can be attributed to the starchy endosperm. Even so the true nature of a genotype with a soft endosperm can be masked by a particularly tough husk, formed from the fusion of the pericarp/testa and lemma and palea.

The integrity of the starchy endosperm depends on the strength of the cell walls and the nature of the protein matrix. Protein and starch granules are intimately associated in the endosperm, particularly the small granules. It has been possible to associate GME with particular proteins which can be extracted from the surface of starch granules isolated from barley endosperms with centrifugation through Cesium Chloride. An examination of the milling energy of malt during the malting process

has shown genotypic differences in endosperm degradation. GME can show significant correlations with components of malting quality but the level of correlation improves markedly when malt milling energy (MME) is considered. The milling energy of barley is greater than that of wheat and selection for important wheat properties could be achieved with the milling energy test.