Hordein and malting quality in northern barleys

The objective of this study was to evaluate the effect of D, C, and B hordein polypeptides on malting quality of 19 spring barley (Hordeum vulgare L.) cultivars. Results from the study indicated that B hordein polypeptide combinations had some effect on malting quality through regulating diastatic power. Comparison of the relative amounts of hordein extracted in the presence and absence of reducing agent was made to determine the effect of disulphide bonds on malting quality. In the absence of reducing agent in the extraction solvent, a high concentration of B hordein was correlated with an increase in extract yield. Conversely, in the presence of reducing agent, an increase in B hordein concentration increased the Kolbach Index. A higher D hordein to B hordein ratio, when the former contained a high concentration of disulphide bonds, decreased malting quality to a greater extent than when fewer disulphide bonds were present. When environmental conditions favoured high N uptake efficiency, a larger proportion of D hordein disulphide bonds was synthesized, leading to decreased malting quality. It is speculated that cultivars with lower grain N yield and a lower D:B ratio yield good quality malt.