I read in some sources that mash conditions can influence the production of dextrins, that are not fermentable, have no taste (is that correct?) and add body to the beer. But somewhere else I read that mash conditions can contribute to sweetness (for example with decoction mash), what kind of compounds are produced during mash that will give some malty flavor or sweetness in finished beer?

  • Could you provide some links to where you read these? Commented Mar 25, 2013 at 16:18
  • byo.com/mashing/item/…, The Complete Joy of Homebrewing - C. Papazian plus some others I do not remeber
    – Paolo
    Commented Mar 25, 2013 at 16:23

3 Answers 3


The mash temperature specifically doesn't really make for a sweeter beer. While adjusting mash temperature allows the brewer to control the balance of simple (fermentable) sugars and dextrins (unfermentable), increasing either doesn't produce a sweeter beer:

  • increasing simple sugars doesn't make the beer sweeter - primarily any sweetness from these sugars is lost when they are fermented.
  • increasing dextrins doesn't increase sweetness considerably, because dextrins are not all that sweet. Dextrins have around 5-10% the sweetness of table sugar.

You may be thinking of melanoidins. These are a class of Maillard reaction compounds - of which there are many, with flavors like bready, malty. Some say richer, sweeter, but not like candy. They are produced with heat in addition to amino acids, proteins and carbohydrates. The high temperature of a decoction mash increases the rate of production of melanoidins. You can also emulate the effect with (Weyermann) Melanoidin Malt, aka Aromatic Malt from other malters.


Note: I am not a chemist. My homebrewing understanding is along the lines of:

Mashing at a higher temperature will promote the alpha-amylase enzyme to breakdown the sugars, while mashing at a lower temperature will promote the beta-amylase enzyme to breakdown the sugars.

The alpha-amylase will produce dextrins which will contribute to sweetness and body.

The beta-amylase will produce fermentable sugars, hence more alcohol.

  • This is interesting and a great practical description of why the temperature balance is so important!
    – xxx
    Commented Mar 26, 2013 at 1:36

Sweetness is pretty much dependent on recipe, not mashing. Using crystal malts or reducing hops will emphasize sweetness. Manipulating mash temps will mainly affect body and mouthfeel.

  • 1
    Also, a low attenuation/high flocculation yeast will help with residual sweetness. Commented Mar 25, 2013 at 18:34
  • Also as is done in popularmechanics.com/home/how-to-plans/… you can pull off some of the mash and caramelize it which will make it unfermentable and add residual sweetness. Also I think adding lactose would add residual sweetness because it isn't fermented by yeast. Commented Mar 28, 2013 at 20:20
  • If by puling off the mash and caramelize it you mean decoction, there are mixed feelings about it. There are a lot of people who feel that doesn't make a difference. My own experimentation seems to confirm that. You can take some of the wort and boil it down to caramelize it to add sweetness, but obviously that's not done in the mash.
    – Denny Conn
    Commented Mar 29, 2013 at 17:52
  • The linked recipe describes a process where some of the first runnings are boiled until reduced to a syrup. Probably won't reach the required temperature to caramalize the sugars, so I doubt this will affect the fermentability of the wort. Commented Mar 30, 2013 at 15:26
  • My experience is that if you boil it down enough, you can achieve caramelization temps. But I haven't found that to be really different than not boiling it quite that far. And as noted, it isn't happening in the mash.
    – Denny Conn
    Commented Mar 30, 2013 at 20:20

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