Maltose effects on barley malt beta-amylase activity and thermostability at low isothermal mashing temperatures

Authors: Henson, Cynthia; Vinje, Marcus; DUKE, STANLEY - University Of Wisconsin

Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2020
Publication Date: 4/7/2020
Citation: Henson, C.A., Vinje, M.A., Duke, S.H. 2020. Maltose effects on barley malt beta-amylase activity and thermostability at low isothermal mashing temperatures. Journal of the American Society of Brewing Chemists. https://doi.org/10.1080/03610470.2020.1738811.
DOI: https://doi.org/10.1080/03610470.2020.1738811

Interpretive Summary: Successful and efficient mashing of malted barley is best achieved by optimizing the process temperature profile and ratio of malt to water to result in the maximal production of fermentable sugars with the desired flavor attributes sought by the brewer. As more and more is known about the performance of the starch degrading enzymes in different varieties of barley it has become apparent that there is a wide range in the performance of different beta-amylases, one of the main enzymes that produces fermentable sugars during mashing. The primary limitation to the performance of beta-amylase during mashing is that it’s activity is diminished or destroyed by high mashing temperatures. The work conducted here demonstrated that there is a type of beta-amylase in some malt varieties that is highly activated by maltose, the major fermentable sugar produced during mashing, below the temperature at which malt starch is fully gelatinized and there is another type that is less activated. This knowledge allows the brewer to choose malts with a beta-amylase that can be highly activated and can benefit from lower mashing-in temperatures if that is desired, or to select malts that do not gain as much from a lower mash-in temperature and start the mashing process at a higher temperature.

Technical Abstract: Maltose increases the activity and thermostability of barley beta-amylase at high mashing temperatures. Here we examined the effects of maltose on malt beta-amylase activity and thermostability at reduced mashing temperatures. Beta-amylase activity was relatively thermostable at both 52 and 58°C with or without added maltose. At 52°C, only 500 mM maltose significantly increased (P=0.0004 to P<0.0001) Harrington beta-amylase activity over mashes without maltose (controls) from 30 to 90 min of mashing. With Morex, at 52°C, 50 to 500 mM maltose significantly increased beta-amylase activity (P=0.0004 to P<0.0001) compared to controls at 60 and 120 min. At 58°C, Harrington beta-amylase activity was significantly increased (P=0.017) only at 120 min with additions of 200 to 500 mM maltose. In contrast, maltose additions to Morex mashes at 58°C significantly increased beta-amylase activities at 30 min (400 and 500 mM), at 60 and 90 min (50 to 500 mM), and at 120 min (100 to 500 mM). This suggests that genotypes with a Morex-like beta-amylase phenotype could benefit from low initial mashing temperatures. Incubations with 0 to 500 mM mannitol at 52 and 58°C were compared with incubations containing maltose and in general mannitol had fewer effects than maltose.