Author
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Henson, Cynthia |
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DUKE, STANLEY - University Of Wisconsin |
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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: Henson, C.A., Duke, S.H. 2016. Maltose effects on barley malt diastatic power enzyme activity and thermostability at high isothermal mashing temperature: I. ß-Amylase. Journal of American Society of Brewing Chemists. 74(2):100-112. 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 increasing the beta-amylase activity in mashing to impact their process outcomes. The impact of the work conducted is it’s demonstrated that inclusion of compatible solutes or the selection of conditions that favor the production of specific compatible solutes results in beta-amylase, a critical contributor to the top two commercial measures of malt quality, producing even greater amounts of fermentable sugars from the same amount of raw material. Technical Abstract: The hypothesis that maltose would increase the thermostability of barley malt beta-amylase activity during isothermal mashing was tested at 68, 73 and 78°C and compared to isothermal mashing at 63°C. Finely ground malts of the two-row cultivar Harrington and the six-row cultivar Morex were incubated in maltose concentrations of 0 to 500 mM at temperatures from 63 to 78°C. Incubations with additions of mannitol from 0 to 500 mM at the same temperatures were used to compare with incubations containing maltose. Incubations were sampled every 30 min for 120 min and beta-amylase activities were determined. Extracts of Harrington had higher beta-amylase activities than did extracts of Morex at 63, 68 and 73°C. Activities of both cultivars were significantly reduced, variable and similar at 78°C. Extracts of both cultivars had highest activities in the absence of exogenous sugars at 63°C and both exhibited maximal responses to sugar additions with 500 mM maltose (889% increase for Morex and 541% for Harrington) compared to 0 mM controls at 63°C. Activities in extracts of both cultivars were significantly influenced by maltose additions starting at 50 to100 mM and as early as 30 min at 63°C and these effects were pronounced at and above 200 mM maltose. Extracts of both cultivars exhibited maximum % survival (85 to 93% for Morex and 90 to 91% for Harrington) at 120 min compared to 0 min when incubations were with 400 and 500 mM maltose at 63°C. A comparison of thermostability of beta-amylases between the cultivars, calculated as the % activity detected at the most favorable condition (0 min at 63°C) that remained at the most unfavorable condition (120 min at 78°C), showed that beta-amylase in Harrington extracts was more thermostable than that in Morex extracts, 10.1% and 5.9% respectively. Activities of beta-amylase in both Harrington and Morex extracts show some increases in activity and thermostability when mannitol was included in incubations which were again most pronounced at 63°C with 500 mM mannitol. However, these effects were not as great or as consistent as seen with maltose additions to the incubations. |
