Mash temperature and time

[rpt]

The mash temperature affects the fermentability of the sugars produced - alpha amylase works better at a higher mash temperature and produces more complex, less fermentable sugars. Beta amylase works at a lower mash temperature and produces simpler, more fermentable sugars. If I have a perfectly insulated mash tun (or some form of heating) I can set a temperature for the full 90 minutes mash time, but in practice I lose 2 degrees over that period. If I do an overnight mash I lose 12C so in that case even if I start at a high enough temperature to favour the alpha amylase at some point the temperature will drop down to the beta amylase temperature and will make simple sugars. So how do I get a nice malty wort? Is it just the starting mash temperature that matters or do I have to ensure that the mash is short enough to never get down to the beta amylase temperature?

 

[graysalchemy]

With any mash it is usually over in a couple of hrs so it doesn't matter if you temp drops significantly after that at the alpha amylase will have done its job before the better has a chance. :thumb:

 

[rpt]

If the mash starts at a high temperature then the alpha amylase will convert starch into complex sugars. As the temperature drops and the beta amylase starts to work, won't it convert the complex sugars into simple sugars?

 

[graysalchemy]

No it is an amylase enzyme which converts starch into sugar not complex sugars into simple ones.

 

[rpt]

Amylase breaks glucose bonds. So why would it break the bond in a starch but not in a sugar?

 

[asd]

I've thought about this too - my understanding is that at the lower temps, the B- amylase will cleave the disaccharides made by the A- Amylase at the higher mashing temps.

However, having done overnight mashes, it doesn't seem to matter too much!

Simon.

 

[graysalchemy]

I mash overnight and haven't noticed a problem with it. The only problem I have is the increased efficiency. :whistle: :whistle:

 

[jonnymorris]

I mash overnight and haven't noticed a problem with it. The only problem I have is the increased efficiency. :whistle: :whistle:

Same here. As I understand it the sugars are converted in the first hour or less so the temp drop overnight won't make a difference.

 

[orlando]

Have a read of this, explains quite a bit about manipulating mash temperatures and the results. However, it is worth taking note of issues like mash pH and grist/water ratio.

 

[rpt]

I think this might explain it:

Alpha works best at 154-162°F, while beta is denatured (the molecule falls apart) at that temperature, working best between 131-150°F.

So I think the beta will break down the complex sugars that the alpha has made, but much of the beta will have been destroyed at the higher temperature. So starting at a high temperature will have the desired effect.

Has anyone here done two identical (or very similar) recipes but mashed overnight at a different temperature and got noticeably different results?