Ask Mr. Wizard

Troubleshooting The “Reverse Step-Mash”


Michael Armstrong — Newcastle, Australia asks,

“These two enzymes, though they work in concert, behave differently in response to changes in mash thickness and mash temperature. This is because of the difference in their stability at high temperatures. Alpha-amylase has an optimal range from 149 to 158 °F (65 to 70 °C). The optimal range for beta-amylase is 126 to 144 °F (52 to 62 °C).”

I perform Brew-in-A-Bag, and am researching mash thickness, then I came across this information in BYO which got me thinking about the temperatures of mashing. If we need the alpha-amylase for the primary process of breaking down the starch molecule chain, then beta-amylase to clip off maltose. Reading the optimum temperatures for these enzymes, then why wouldn’t mash temperature profiles have a stand at “149 to 158 °F (65 to 70 °C),” then back the temperature off to “126 to 144 °F (52 to 62 °C)” to optimize conversion?

The old alpha and beta amylase temperature conundrum! It does indeed seem that the temperature optima for these two enzymes is reversed for the purpose of mashing. Beta amylase produces maltose by
Response by Ashton Lewis.