Kernel hardness, an important quality trait of cereal grains, is known to influence pearling properties and malting quality of barley. To understand the endosperm micro-structural features of kernels and their relationship to kernel hardness, endosperms of three hard and three soft hulled spring barley lines based on single kernel characterization system hardness index were observed under light (LM) and scanning electron (SEM) microscopy. Under LM, endosperm cell wall of the three hard kernel lines was significantly thicker than that of the three soft kernel lines. Hard and soft lines showed differences in the degree of starch-protein association and continuity of protein matrix under the SEM. Hard kernel lines with a continuous protein matrix exhibited greater starch-protein adhesion than the soft kernel lines, suggesting that starch-protein binding may be one of the factors influencing barley kernel hardness. SEM of flour particles of soft kernel lines showed numerous well defined individual A and B-type starch granules, while, flour of hard kernel lines mostly showed small flour aggregates with few individual starch granules.
