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Title: Comparisons of modern United States and Canadian malting barley cultivars with those from pre-Prohibition:IV. Malting quality assessments using standard and nonstandard measures

Author
item Henson, Cynthia
item DUKE, STANLEY - University Of Wisconsin
item Bockelman, Harold

Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2018
Publication Date: 11/1/2018
Citation: Henson, C.A., Duke, S.H., Bockelman, H.E. 2018. Comparisons of modern United States and Canadian malting barley cultivars with those from pre-Prohibition: IV. Malting quality assessments using standard and nonstandard measures. Journal of American Society of Brewing Chemists. 76(3):156-168. https://doi.org/10.1080/03610470.2018.1492818.
DOI: https://doi.org/10.1080/03610470.2018.1492818

Interpretive Summary: Local production of barley, malt and beer has increased in economic importance throughout the US during the past decade and continues to garner significant attention as locavore commodities. Frequently desired germplasm for production of these craft commodities are older varieties considered to be ‘heirloom’ varieties. The work presented here was conducted to identify which traits or combination of traits associated with malting quality and mashing performance could best define the differences between a population of pre-Prohibition malting barley varieties and a population of modern elite malting barley cultivars. The values of three traits (malt extract, osmolyte concentration and glucose concentration) together best separated the modern cultivars from the pre-Prohibition cultivars. These particular traits are significant to the malting industry as malt extract is considered the most important criteria in determining the value of malting barley as a commodity of commerce, osmolyte concentration has been demonstrated to be an excellent predictor of the amount of glucose and other fermentable sugars produced during mashing, and glucose is the most preferred fermentable sugar of many strains of brewer’s yeast. This work also identified two pre-Prohibition cultivars that had either the same or almost the same values of these three traits and additionally were comparable in values of the single most abundant fermentable sugar (maltose) produced during mashing. The impact is that two pre-Prohibition cultivars were identified that can satisfy the fermentation requirements of niche market brewers.

Technical Abstract: This study was conducted to identify which traits or combination of traits associated with malting quality and mashing performance could best define the differences between and within a population of pre-Prohibition malting barley varieties and a population of modern elite malting barley cultivars. To accomplish this, standard and nonstandard metrics of malt quality and of performance during Congress mashing were analyzed by simple linear correlations and multivariate statistics. Analyses of the two populations combined revealed that activities of a-amylase at each time point during mashing were positively and significantly correlated with the concentrations of glucose at that same time point, were not significantly correlated with maltose concentrations at any time point, and were only significantly correlated with maltotriose concentrations for the first 30 min of mashing. Activities of ß-amylase showed no significant correlations with concentrations of glucose, maltose or maltotriose at any time during mashing. Analysis of a-glucosidase activities showed no consistent trends in correlations with either glucose or maltotriose and no significant correlation with maltose at any time. Analysis of limit dextrinase activities showed significant and positive correlations with glucose and maltotriose concentrations prior to the mash temperature reaching the starch conversion stage. Although no individual amylolytic enzyme activity was significantly correlated with maltose concentration, diastatic power was positively and significantly correlated with maltose at five of six time points during mashing. Diastatic power was not significantly correlated with glucose or maltotriose concentrations at any time. Malt extract values and osmolyte concentrations were positively and significantly correlated with mash glucose concentrations at all times sampled, with maltose concentrations at the first four times sampled, and with maltotriose for the first five times. Principal component analysis (PCA) of the traits analyzed in the two populations combined showed the modern malting barleys were generally well separated from the pre-Prohibition barleys by three principal components that accounted for 81% of the variation among the 11 cultivars. The traits that collectively contributed the most to separation of the modern from the pre-Prohibition barleys were osmolyte concentrations, malt extract values and glucose concentration, which were higher in the modern cultivars, and a-glucosidase thermostability and concentrations of maltopentaose, maltohexaose and maltoheptaose, which were higher in the pre-Prohibition cultivars. PCA of the individual populations also separated Tradition from the other modern cultivars due to its lower levels of glucose, maltotriose and a-amylase activity and by its higher levels of maltose and % plump. PCA of the pre-Prohibition population separated Hanna from the other pre-Prohibition cultivars primarily by its higher levels of maltopentaose through maltoheptaose and its low levels of OC. Silver King was somewhat displaced from other pre-Prohibition cultivars due to its low levels of OC and to its very high levels of a-glucosidase thermostability.