Grain and endosperm biophysical characteristics of barley malting

Cultivated barley (Hordeum vulgare), derived from its wild progenitor Hordeum vulgare ssp. spontaneum, is among the world’s earliest domesticated crop species, adapted to diverse environments and today represents the fourth most abundant cereal in both area and tonnage harvested. Malting quality is an economically important character of barley. Malsters require grains of known varieties with consistent quality and specify strict quality criteria for accepting new varieties. As starch is the major component of the barley grain changes in its biophysical or biochemical properties will have a direct effect on its malting properties. In order to achieve good malting quality, extensive endosperm breakdown, or modification, must accompany the germination phase of malting, with cell walls and protein being degraded and the starch granules exposed during the process. Hot water extract (HWE) of the resultant malt should yield a high of level of fermentable sugars from readily gelatinised starch granules that are depolymerised by malt amylases. Many characteristics or properties of the grain and endosperm drive these characteristics among them starch (amylose and amylopectin), protein (hordein composition), lipids content, fatty acid profile, hardness, particle and granule size. However, other bio-physical properties or characteristics of the grain can also explain or modulate malting properties such as starch pasting properties (e.g., viscosity), water uptake, cell wall content, and interaction of chemical constituents (e.g., amylose and lipids). This chapter will provide an overview and discussion of some of the biophysical characteristics of barley grain and endosperm that have been reported to have an influence on malting quality. The main focus of this chapter is on starch characteristics, chemical interactions with the main grain chemical components and water uptake.