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United States Department of Agriculture

Agricultural Research Service

Title: The Thermal Stabilities of Barley Chymotrypsin Inhibitors

Authors
item Mikola, M - UNIVERSITY OF WISCONSIN
item Jones, Berne

Submitted to: Brewers Digest
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 1998
Publication Date: N/A

Technical Abstract: Chymotrypsin inhibitors (CI) are small proteins that are widely distributed among cereal seeds. Their probable physiological role is to protect the seed from pest and pathogen attacks. Ryan (Ann. Rev. Phytopathol. 28:425-449. 1990) has proposed using various proteinase inhibitors, such as the CIs, as plant protective agents. Two groups of barley CIs have been characterized, the CI-1 proteins which are inactivated at about 60C, and their CI-2 counterparts, which are relatively stable at 100C (Boisen, et al. Physiol. Plant. 52:167-176. 1981). Our goal was to examine the fate of the CIs during malting by separating and analyzing them. During malting, some new activities formed that were mainly localized in the rootlets. Most of the rootlet CIs were stable to boiling temperatures, whereas resting seed inhibitors having similar electrophoretic mobilities were not. Of the individual CI activities extracted from ungerminated barley, all were stable at 60C, but half were inactivated at 70C. Kilning to 85C did not inactivate the malt CIs. The good thermal stabilities of the inhibitors imply that some of them may survive the brewing process and persist in beer. Analysis of five Hordeum spontaneum accessions showed that they contained different combinations of CI proteins. The five spontaneums contained, in totality, seven CI forms.

Last Modified: 7/28/2014
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