|DUKE, STANLEY - University Of Wisconsin|
Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 2/2/2018
Citation: Duke, S.H., Henson, C.A., Bockelman, H.E. 2018. Comparisons of modern United States and Canadian malting barley cultivars with those from pre-Prohibition: III. Wort sugar production during mashing. Journal of American Society of Brewing Chemists. 76(2):96–111. https://doi.org/10.1080/03610470.2017.1402582.
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 to compare the mash performance of some of the major varieties commonly grown during the early part of the 21st century with the performance of varieties released for malting in the US in the past 20 years. This study used a common mashing procedure, called a Congress mash, to determine if the heirloom malts produced adequate levels of fermentable sugars to support fermentation by brewers’ yeast. It was shown that the final mash products, the worts, made by heirloom barley varieties contained equivalent levels of maltose, the majority of the fermentable sugar produced during mashing and that sugar most rapidly taken up by yeast, and maltotriose as did worts produced by modern cultivars. The modern malts did produce worts with higher levels of glucose than did the heirloom malts. The amount of ‘glucose equivalents’ from fermentable sugars (i.e. the amount of glucose from glucose plus that from all the hydrolyzed fermentable sugars) were not significantly different between the heirloom and modern cultivars. The impact of this work is that several heirloom malting barley cultivars have been identified that can satisfy the requirements of modern craft brewers, thus providing opportunities for niche market production.
Technical Abstract: This study was conducted to compare wort sugar production during mashing of barley malts of pre-Prohibition varieties and modern elite cultivars. Four of the five modern cultivars utilized were significantly higher (P<0.0001) in glucose production than all six pre-Prohibition barley varieties at all six time points assayed during Congress mashing. Throughout mashing, the average values for glucose production were very significantly higher (P values ranging from 0.0002 at 75 min to 0.0021 at 45 min) for the combined means of modern malt cultivars as compared to those of six pre-Prohibition malts. In contrast, maltose production was quite variable amongst both pre-Prohibition barley and modern genotypes throughout mashing with modern and pre-Prohibition genotypes ranked significantly (P<0.0001) in both the highest and lowest tiers of maltose production. Both Manchuria (pre-Prohibition) and Tradition (modern) produced the significantly (P<0.0001) highest levels of maltose at all six time points during mashing. The averages of maltose production of combined modern versus pre-Prohibition malt genotypes were not significant throughout mashing and were statistically equal by the end of mashing. As with maltose production, maltotriose production during mashing was quite variable with pre-Prohibition and modern barley genotypes both ranking significantly (P<0.0001) in the highest and lowest tiers of maltotriose production throughout mashing. Harrington (modern cultivar) wort maltotriose levels were statistically higher (P<0.0001) than any other genotype at the end of mashing. Although the combined modern genotypes produced statistically higher levels of maltotriose at two time points during mashing, by the end of mashing the pre-Prohibition and modern genotypes had produced statistically the same levels of maltotriose (P=0.514). Levels of glucose equivalents from fermentable sugars (i.e. the amount of glucose from glucose plus hydrolyzed maltose and maltotriose) followed almost an identical pattern as that for maltose. Levels of the non-fermentable maltodextrins, maltotetraose through maltoheptaose, were variable with both pre-Prohibition and modern barley genotypes throughout mashing. Except for maltohexaose and maltoheptaose at 115 min, from 60 to 115 min of mashing, Hanna and Hannchen (pre-Prohibition) were significantly higher (P<0.0001) than all other genotypes for maltotetraose through maltoheptaose. There were no significant differences in genotypes for maltohexaose and maltoheptaose at 115 min due to undetectable levels of maltoheptaose in all genotypes and only two genotypes (Hanna and Hannchen) with detectable levels of maltohexaose. Due to the very large amount of variability amongst genotypes, there were no significant differences for the averages of the combined means of maltotetraose through maltoheptaose for pre-Prohibition and modern barley genotypes. Sucrose levels remained relatively constant throughout mashing amongst most pre-Prohibition and modern barley genotypes. At 5 min into mashing the average for the combined means of modern barley genotypes was significantly higher (P=0.0403) than for pre-Prohibition genotypes. Levels of fructose increased throughout mashing for all genotypes. The average fructose levels for the combined means of modern barley genotypes were significantly higher than those for pre-Prohibition genotypes at most time points in mashing.