To get the starch to convert to sugars for fermenting requires the action of alpha and beta amylase. Alpha amylase breaks down the starches to long chain sugars, beta amylase breaks the long chain sugars to short chain, fermentable sugars. You need to mash in the range where both of them work. If I interpret this graph correctly, about 143F would be the minimum to get both working and the alpha amylase activity would be minimal so you would need more time for it to work.
You can't do that, because at the higher temperatures it's not just a matter of beta amylase being less active; it actually begins to denature (which renders it permanently inactive). This apparently takes more time than most brewers would be led to believe - it's always implied that beta "dies" instantly at 158 - but in a long mash, it would certainly happen.
Hey @RM-MN, I've read your short mash time posts many times and it has always interested me. I've wondered, though: even though the conversion of starches to sugars may occur quickly, isn't it still necessary to allow beta amylase some more time to shorten the dextrins into maltose?
Similarly, I thought beta worked fairly slowly at lower mash temps, so I would think that really short mashing would be practical only at higher temps, which limits its usefulness.
Just wondering if you've made any observations about this in your brewing...? Thanks!
@dmtaylor. Interesting theory...how do you think that would affect a step mash, or possibly a "ramp" mash? IDK if that's a real term, but describes what I mean by mashing in low (say ~140⁰ then slowly raising the mash temp to mashout at ~ 165-8⁰ over the period of 40-60 minutes? Would that not also give the Beta & Alpha-Amylase the best chance for conversion?
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