Comparisons of Modern U.S. and Canadian Malting Barley Cultivars with Those from Pre-Prohibition: II. Amylolytic Enzyme Activities and Thermostabilities

ABSTRACT

Amylolytic enzyme activities and thermostabilities in North American pre-Prohibition and modern malting barley cultivars were compared throughout Congress mashing. The mean α-amylase activity was significantly higher in modern cultivars throughout mashing than in pre-Prohibition varieties, although the reverse was observed for mean thermostabilities, expressed as percent of initial activity. The mean limit dextrinase activity in modern cultivars was higher early in mashing than in pre-Prohibition varieties, but modern cultivar mean thermostability was less than in pre-Prohibition varieties at the end of mashing. There were no significant differences in population means for β-amylase or α-glucosidase activities during mashing although mean thermostabilities for both enzymes were greater in pre-Prohibition cultivars than in modern cultivars. A comparison of individual genotypes showed the four highest α-amylase activities were in modern cultivars, with Charles having the most thermostable (116%) and Tradition the least thermostable (21%). Among pre-Prohibition cultivars, Oderbrucker (132%) and Manchuria (127%) had the most thermostable α-amylases. Hanna and Manchuria had the highest β-amylase activities at 30 and 45 min of mashing. No cultivar had β-amylase activity beyond 45 min of mashing. At the end of mashing, Silver King, Hannchen and Oderbrucker had the highest α-glucosidase activities and thermostabilities (88, 52, and 53%, respectively). Among modern cultivars, highest α-glucosidase activities and thermostabilities were in Metcalfe (39%), Tradition (47%) and Charles (42%). The highest limit dextrinase activities, followed by their thermostabilities, at the end of mashing were in Manchuria (57%) and Hannchen (60%) followed by Tradition (44%), Metcalfe (26%) and Charles (37%).

KEYWORDS:

• α-amylase
• β-amylase
• α-glucosidase
• limit dextrinase
• thermostability

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.

Funding

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

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.