Recipe calls for mashout at 158°F?

[JstnMoyer]

I brewed a RIS last weekend (BIAB, brew #13) based on this Old Rasputin clone recipe. I followed a lot of the process it calls for including a 60 minute mash at 152°F and a mash out at 158°F/70°C. I have been really interested in reading about the science of malting & mashing so I've done a lot of reading this week. 158F doesn't seem to make sense for mash out temp and I'm seeing 167-170F is proper.

Was this likely a typo? To me, it seems like I will have some extra unfermentable sugar. Anyone else mashout at this temp and what might I expect?

 

[McKnuckle]

Could have meant to say 168, although the Celsius conversion follows the typo. Nevertheless, ~170ºF is the norm for a mashout, so you did not technically perform one, and the recipe's directions are misleading.

Following the recipe, 152º for 60 min. and 158º for 10 min., I would not expect much more activity, certainly not enough to notice. Alpha amylase works fairly quickly, and the first long rest likely got all the starch converted. If anything, the rise to and hold at the higher temp would have finished it off if any conversion was remaining. It also would have put an end to beta amylase activity, but again, with only 10 minutes, it's only a minor curtailment than if it had stayed at 152 for that time.

In short, absolutely no big deal - just trying to explain what I'd assume occurred.

 

[JstnMoyer]

Ok - that's what I was thinking and hoping. I'm still learning the benefit of a mashout in general. I just do it because it's what you do. Mashing out in the 170° range puts a stop to enzymatic activity but after a 60 minute sac rest, what enzymatic activity would there still be? Those beta amylase still doing much?

 

[RM-MN]

The beta amylase in the grain will not have been doing anything, presuming you did not already have full conversion. The starches have to be gelatinized before the enzymes get to work and you may still have ungelatinized starch in the grain particles. Heating the mash to 158 will denature the beta enzyme but not immediately and while some of it is still active, the higher temps will speed up the alpha amylase so the beta can work on the ends of the starch molecules getting you higher conversion.

 

[BrewnWKopperKat]

Was this likely a typo?

Agreed, it's likely a typo.

AHA recipes will occasionally "call out" out a unique process step or use of ingredients (sometimes in the related magazine article). I didn't see a "call out" in a quick search / skim of the digital copy of that issue of the magazine.

 

[McKnuckle]

A bit more to the point about what might be happening after a one hour rest at 152°... there is still beta activity happening. Many pro breweries mash for 90-120 minutes in order to produce more fermentable sugars, even if the mash started higher. And always if the mash is conducted on the low side.

Even though conversion from starch may be complete at a given point, some of the converted sugars are still of the long chain variety. Beta amylase works slowly, so these extended mash rests are useful if the brewer is trying to maximize fermentables.