Comparisons of Modern United States and Canadian Malting Barley Cultivars with Those from Pre-Prohibition: IV. Malting Quality Assessments Using Standard and Nonstandard Measures

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 six pre-Prohibition malting barley varieties and a population of five 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 α-amylase at each time sampled during mashing were positively and significantly correlated with the concentrations of glucose at that same time, were not significantly correlated with maltose concentrations at any time, and were only significantly correlated with maltotriose concentrations for the first 30 min of mashing. Activities of β-amylase were not significantly correlated with concentrations of glucose, maltose, or maltotriose at any time during mashing. Analysis of α-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 times sampled 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 that the modern malting barleys were generally well separated from the pre-Prohibition barleys by three principal components that accounted for 75% 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 α-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 α-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 osmolytes. Silver King was somewhat displaced from other pre-Prohibition cultivars due to its low levels of osmolytes and to its very high levels of α-glucosidase thermostability.

KEYWORDS:

• Amylolytic Enzymes
• diastatic power
• enzyme thermostability
• fermentable sugars
• glucose
• malt extract
• maltose
• osmolyte concentration
• wort sugars

Acknowledgments

We thank Joseph T. Dietrich, Charles B. Karpelenia, and Andrew J. Standish for their expert technical assistance. We thank Gongshe Hu and staff for the production of the seed used to generate the malts for this study and Christopher H. Martens and staff for generating the malts.

Disclosure

Mention of a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other suitable products.

Additional information

Funding

Financial support was provided by the U.S. Department of Agriculture’s Agricultural Research Service and the American Malting Barley Association, Inc.