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Gamma amylase rest

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mattclough

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Has anyone ever experimented with a gamma amylase rest during a mash? I understand that the optimal conditions for gamma amylase are a pH of about 3 and a temp of about 113F (45C). I'm curious about gamma amylase because my understanding is that gamma amylase can cleave off both 1,4 and 1,6 glycosidic bonds which seems to mean that it leaves less unfermentable sugars than alpha amylase and also works more efficiently than beta amylase. Sounds like a golden enzyme to me. The only way I can think to use naturally occuring gamma amylase though is to take the pH of the mash super low during the first step, then add some higher pH water in progressive steps to raise the pH for other enzymes to work. Has anyone tried this?
 

edds5p0

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If there is G-amylase in barley, I would suspect that the rest to optimize its activity would make a very dry beer. From what I can tell, this is the enzyme most responsible for hydrolyzing the starches in rice for sake making. A pH of 3 may do more harm than good as you may denature some other enzymes in your mash. The temperature would also favor proteases, meaning you would be left with little in the way of head retention and body. All that being said, if you decide to try it I would love to hear about the results. As a chemist, I appreciate those who experiment. To adjust pH, I would probably use a mineral acid like phosphoric as it shouldn't impact flavor too much and would require minimal addition. Then, you could add potassium or sodium phosphate to bring it up.
 
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any particular reason you'd be investigating this? It sounds like it will give you good attenuation, but unless you are looking for super attenuation in lager settings (light american lager?) Can't see why a 148-149 rest wouldn't do just fine.

Sounds like a fine idea, just wondering why it would be necessary.
 

Seedly

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I would focus on limit dextrinase, which can break 1-6 bonds. Its optimum temp is similar to beta amylase at 140-145°F and ph of 5.1, both of which will not harm your mash. Just remember that the limit dextrins left over by the alpha and beta amylase contribute a large part of the body of the beer. Its going to be extremely light in body.

Besides which, i dont think there is much gamma amylase in barley anyway.
 

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