Author
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DUKE, STANLEY - University Of Wisconsin |
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Henson, Cynthia |
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Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/17/2016 Publication Date: 4/21/2016 Citation: Duke, S.H., Henson, C.A. 2016. Maltose effects on barley malt diastatic power enzyme activity and thermostability at high isothermal mashing temperature: II. Alpha-amylase. Journal of American Society of Brewing Chemists. 74:113-126. Interpretive Summary: Solvent engineering with the intent of directing the outcome of processes to favor specific reaction products is a well established tool used by many industries. In the context of brewing, solvent engineering might be driven by choice of malt(s) and additives used in mashing, the choice of mashing regime, choice of mash solvent concentration, choice of yeast and additives used in fermentation and fermentation conditions. This work was done to determine if regulating the concentration of a compatible solute that is also a preferred fermentable sugar might a useful solvent engineering option for brewers to consider for directing the alpha-amylase action in mashing to impact their process outcomes. The work conducted demonstrated that inclusion of compatible solutes or the selection of conditions that favor the production of specific compatible solutes will result in the malt enzymes producing even greater amounts of fermentable sugars. Technical Abstract: Maltose, the primary product of starch degradation during mashing, has the potential as a compatible solute to affect the activity of and increase the thermostability of barley malt alpha-amylase activity at high temperatures used in mashing and temperatures above those normally used in mashing. To determine if this occurs, malts of the two-row cultivar Harrington and the six-row cultivar Morex were ground to a fine powder and incubated with maltose concentrations of 0 to 500 mM at temperatures from 63 to 78°C. Incubations were sampled every 30 min for 120 min and alpha-amylase activities determined utilizing the Megazyme Ceralpha assay. Mannitol, a polyhydric alcohol, was used for comparison. Polyhydric alcohols are known to enhance enzyme thermostability. At 63°C both cultivars had relatively thermostable alpha-amylase without the addition of maltose or mannitol. However, Morex, and to a lesser extent Harrington, alpha-amylase activity was significantly enhanced by high levels of either thermoprotectant. At 73 and 78°C increasing concentrations of maltose conferred considerable and highly significant (LSD analysis, P<0.0001) thermal protection of alpha-amylase in both cultivars. For example, at 30 min of 73°C incubation, 400 and 500 mM maltose, respectively, resulted in higher alpha-amylase activity in Harrington of 227 and 252% and in Morex 349 and 314% of the 0 mM maltose activity. At of the 60 min incubation 73°C incubation, 400 and 500 mM maltose, respectively, alpha-amylase of Harrington was 290 and 431% and Morex was 489 and 501%, of 0 mM maltose activity. High mannitol incubations at higher temperatures at 73 rendered lesser alpha-amylase thermal protection than maltose; however, it was also considerable and highly significant (P<0.0001) for both cultivars (e.g. 30 min incubation at 73°C, with 400 and 500 mM maltose, respectively, alpha-amylase of Harrington was 163 and 174% and Morex was 188 and 260% of activity at 0 mM maltose). These data suggest that the production of maltose, especially in high gravity mashes, should significantly increase the thermostability of barley malt alpha-amylase. |
