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Title: Comparison of modern United States and Canadian malting barley cultivars with those from pre-prohibition: I. Malt extract and osmolyte concentration

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

Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2016
Publication Date: 4/21/2017
Citation: Duke, S.H., Henson, C.A., Bockelman, H.E. 2017. Comparison of modern United States and Canadian malting barley cultivars with those from pre-prohibition: I. Malt extract and osmolyte concentration. Journal of American Society of Brewing Chemists. 75(2):85-92.

Interpretive Summary: Sustained increased interests over the past decade in the use of locally grown crops in local production of small batch, craft malt beverages combined with increased interests in the use of ‘heirloom’ varieties resulted in a series of studies to compare a broad spectrum of malt quality traits of pre-Prohibition malting barley cultivars with those of modern malting barley cultivars. This report, the first in the series, compares gross physical traits of the barley kernels and percent kernel protein. Additionally, this report compared changes in malt extract, the traditional measure of malt quality, and the more recently developed measure of osmolyte concentration throughout the mashing procedure in these two different groups of malting barley. Mashing is the process of extracting malt to make the nutrient solution that supports fermentation by brewers’ yeasts. The results show that modern malting barley kernels are plumper, have a narrower range in protein content and a lower amount of kernel protein. These are all desirable changes over time that reflect the expressed preferences of maltsters and brewers and, therefore, have directed the nation’s malting barley breeding programs for decades. Interestingly, the malt extract values were significantly higher in the modern cultivar population than the heirloom population only for the first hour of the mashing process, but were the same at the end of the mashing process. In contrast, the osmolyte concentrations were significantly higher in the modern cultivar population than the heirloom population for the entire mashing process. The impact of this work is the identification of two heirloom varieties, Silver King and O.A.C. 21, with the potential to meet the processing needs and interests of craft maltsters and brewers and a database directly comparing heirloom and modern cultivars. The heirloom cultivar Silver King was significantly higher in malt extract than all other cultivars, including all modern cultivars, at the end of mashing and the heirloom cultivar O.A.C 21 had significantly higher osmolyte concentrations throughout mashing.

Technical Abstract: United States and Canadian pre-Prohibition and modern elite malting barley cultivars were evaluated for gross kernel characteristics (i.e. plumpness, thins, kernel protein) and development of malt extract (ME) and osmolyte concentration (OC) over the course of Congress mashing to determine malt quality improvement in these phenotypic traits since the end of Prohibition. Kernel plumpness was considerably higher in modern barley cultivars (96.1±1.1%) as compared to pre-Prohibition cultivars (84.1±9.4%). However, kernel weight was only slightly higher in modern cultivars (48.9±2.6 mg) as compared to pre-Prohibition (46.3±2.5 mg). This difference in kernel density suggests that pre-Prohibition kernels are prone to be steely and modern kernels are prone to be mealy. This led to the hypothesis that modern cultivars would develop ME and OC more rapidly than pre-Prohibition cultivars during mashing. There was considerable variation in pre-Prohibition cultivar development of wort ME and OC as compared to modern cultivars over the course of mashing. Modern cultivars developed both wort ME and OC considerably more rapidly early during mashing, suggesting that their malts were considerably more modified than pre-Prohibition cultivars, possibly due to mealy kernels. This supports the aforementioned hypothesis. Except for the last time point in mashing, modern cultivars had higher OC levels than pre-Prohibition cultivars throughout mashing. Also, except for the pre-Prohibition cultivar O.A.C 21, the significantly (P>0.0001) highest OC levels were in modern cultivars throughout mashing. Also, means of modern cultivar OC values at each time point were always significantly (P=0.0005 to 0.0029) higher than pre-Prohibition cultivars. This is in contrast to changes in ME for pre-Prohibition cultivars over the course of mashing where the pre-Prohibition cultivar Silver King was significantly (P>0.0001) higher than all other cultivars at the end of mashing and means of ME modern and pre-Prohibition cultivars were not significantly different at 75 and 115 min into mashing. These data indicate that measures of wort OC indicate the superior performance of modern cultivars in mashing better than measures of wort ME.