Mash time based on starch conversion

[pingeyeg]

I'm just curious about something I've been researching. I've watched a few videos where they say, once the Iodine appears clear, the starch conversion is complete, which could be anywhere from 20 to 50 minutes. However, I read a Kolsch recipe where they said to Mash for 90 minutes. If the starch conversion can be that quick, why the need to Mash for the full 90 minutes? Does that extra time make the style that much better or does it really matter?

 

[TexasDroughtBrewery]

Honestly...ive never mashed for longer than 60 mins and never had a problem. I couldn't give a reason why you would mash for 90..maybe someone else can...Id like to hear it too.

With the exception of decoction mashing.

 

[BobBailey]

Kolsch is usually mashed at 150F or lower. Conversion takes longer at lower temperatures. That's just the nature of enzymatic action.

 

[Chanoc]

For what I understand, it is not just conversion, but for obtaining more fermentables and lowering body..

 

[doug293cz]

For what I understand, it is not just conversion, but for obtaining more fermentables and lowering body..

Yes. To expand on this, iodine will indicate absence of starch while you can still have lots of unfermentable sugars in the wort. Extending the mash time will allow the amylase to chop more of those unfermentables into fermentables. So, for dryer, lighter bodied beers, longer mash times may be appropriate.

Also, if you conduct your iodine test just on wort (no grain grits) the wort may be free of starch, but the grits can still contain starch. Starch gets converted very quickly once it is in solution. Unconverted starch in the grits will lower your conversion efficiency. A better test for conversion completion is measuring the SG of the wort in the mash, as described here.

Brew on

 

[pingeyeg]

Wow, that link you posted is highly complex. Made my eyes cross

Makes sense as to what you guys have said. Sense the water temperature will be lower than usual, the conversion will take longer. That being said, even though the starches have converted, doesn't mean everything else is good to go. I'll stick with my typical 60 minute mash time or longer pending the temperature.

Thanks!

 

[doug293cz]

Wow, that link you posted is highly complex. Made my eyes cross

Makes sense as to what you guys have said. Sense the water temperature will be lower than usual, the conversion will take longer. That being said, even though the starches have converted, doesn't mean everything else is good to go. I'll stick with my typical 60 minute mash time or longer pending the temperature.

Thanks!

Yeah, there is some heavy duty stuff in Kai's writings. You don't need to understand everything to make use of the SG method for determining conversion completeness, however. You just need to know that the maximum SG is determined by the water to grain weight ratio. (It actually depends to some extent on the extract potential of the particular base grains, but in practice they are mostly pretty close to each other.) So, if you know how many qt/lb (or liters/kg) you have in your mash, the table will tell you approximately what your SG will be after conversion is 100% complete. To estimate your percent conversion just use the following simple formula:

Percent Conversion = 100% * (Measured Mash SG - 1) / (Table SG - 1)​

Percent conversion is the same as conversion efficiency.

Brew on