The Effect of Cultivar Mixtures on Malting Quality in Winter Barley

Abstract

A range of winter barley cultivars was grown, either as pure stands or as components of mixtures, in a trial in 1995-96. For malting quality characters, mean values of mixtures did not differ from mean values of the appropriate monocultures, except for decreases in homogeneity, as determined by a fluorescence test of cell wall modification. When disease pressure was modified by fungicide, hot water extract was not significantly altered, although this may have been due to the restriction of malting to grain retained by a 2.5 mm sieve. One mixture, comprised of three related winter malting cultivars, gave higher hot water extracts than its components, as pure stands, with no adverse effects on homogeneity. This was not simply attributable to lower grain nitrogen content.

Barleys Grown as Cultivar Mixtures Compared with Blends Made Before and After Malting, for Effects on Malting Performance

“…For grain characters and for malt ␤-glucan and soluble nitrogen, analysis of variance was performed separately on varieties and mixtures, as previously described 15 .…”

“…Much of the previous work on barley mixtures (reviewed by Finckh et al 4 ) was concerned with reduction of disease and components were frequently chosen on the basis of diversity in resistance genes. Where quality characters were assessed, mixtures were generally considered to give values similar to the mean of the component cultivars 29 and inclusion of poorer quality varieties within a mixture led to unacceptable levels of malting quality 15 . Following German unification, however, the use of barley mixtures in malting was terminated, so, where barley mixtures are currently grown, it is generally as a source of animal feed.…”

“…The view expressed by Schildbach 18 , that cultivation of barley mixtures would only be viable commercially if a standard of quality and, particularly, homogeneity acceptable to maltsters and brewers was achieved, persisted for many years 23 . Recent research has indicated, however, that carefully chosen barley mixtures can perform extremely well in laboratory-scale malting 15,23 . In particular, heterogeneity of cell wall modification may not be significantly increased 15 .…”

“…Recent research has indicated, however, that carefully chosen barley mixtures can perform extremely well in laboratory-scale malting 15,23 . In particular, heterogeneity of cell wall modification may not be significantly increased 15 . Additionally, molecular methods for varietal identification are capable of detecting very low levels of mixing 6 , so should permit the composition of any mixture to be verified.…”

“…In addition the effect of environments, other than the field, has not been considered, although both the malting and mashing environments are likely to influence factors such as hot water extract and fermentability. Newton et al 15 suggested that the malting environment may have the lesser effect, as the integrity of individual grains is maintained, but that, during mashing, the balance of enzymes and substrates could differ in a mixture compared to a single variety. Swanston et al 19 thus offered a possible mechanism for the improved performance of certain mixtures compared to their component cultivars.…”