The Relevance of Different Enzymes for the Hydrolysis of β-glucans in Malting and Mashing

Abstract

J. Inst. Brew. 114(3), 224-229, 2008 β-Glucosidase and to a lesser extent endo-β1-4-glucanase are present in significant quantity in raw barley. These enzymes, as well as endo-β1-3, 1-4-glucanase, endo-β1-3-glucanase and exo-β1-3-glucanase, increase in activity during steeping and germination. Exo-β1-3-glucanase stands apart through its very late development during germination and it may be a limiting enzyme in malts that have not received substantial modification. Three separate exo-glucanases were located in malt and each of them displayed a preference for β1-3 linkages. As the principle product of endo-β1-3, 1-4-glucanase is oligosaccharides with a β1-4 linkage at the non-reducing end (from which end exo enzymes approach the substrate), this is likely to be a second reason (alongside the late development of the enzyme) why such oligosaccharides survive in significant quantities into wort. A third contributing factor may be the sensitivity of the exoglucanases to ions such as potassium, sodium and magnesium.

Changes in saccharide, amino acid and S-methylmethionine content during malting of barley grown with different nitrogen and sulfur status

“…Even well‐modified malt still contains a small amount of β‐glucan, and further depolymerisation seems to proceed more slowly 25. A recent report suggested significant involvement of exo ‐1,3‐β‐ D ‐glucanase in the degradation of β‐glucan, which developed during late germination 26. Thus the importance of a longer germination period to lower the β‐glucan content of wort may be associated with the induction of this enzyme activity.…”

The Horace Brown Medal. Forever in focus: researches in malting and brewing sciences

“…Using a radial diffusion assay for endo‐β‐glucanase , we investigated this enzyme and inter alia discovered that it might be partially stabilised and made more resistant to heat by reduced glutathione . That the end products of β‐glucan degradation in malting and mashing are oligosaccharides rather than glucose was explained by the finding that the exo‐glucanases that are present and capable of yielding glucose do not do so because of a poor affinity (high K m ) for the products of the endo‐β‐glucanase action and, furthermore, these enzymes develop relatively late during germination .…”

125thAnniversary Review: Barley research in relation to Scotch whisky production: a journey to new frontiers

“…The main compounds present in barley that need to be hydrolysed are starch, protein and cell wall polysaccharides. As well as the standard starch and protein‐degrading enzymes, the malting process provides all of the necessary enzymes that are necessary to achieve malt modification .…”

“…Modern studies highlight the complexity of the links between barley cell wall arabinoxylans and β ‐glucans and other polymeric materials (such as proteins), and how these interactions impact on how the cell wall are degraded. Kanauchi and Bamforth emphasize the fundamental importance of malting in the development of the enzymes that will digest the endosperm cell walls and ensure the optimal solubilization and removal of β ‐glucans, in order to minimize potential problems with viscosity and wort separation.…”