Falling Mash Temp and Enzyme Conversion

Hi Everyone,

I'll try to keep this short and to the point.

I mash in a 10 gallon Igloo cooler. Temperature in the cooler drops at a rate of approx 1-1.5 degrees an hour depending on mash volume. I have found that mashing between 90-120 minutes will typically guarantee hitting my target OG.

Preface and question:

It is my understanding that most conversion happens within the first 20-30 minutes of a mash. A lower mash temp will equal a lower FG, higher mash temp will equal a higher FG, due to the sugars in the grains being broken down into chemical chains of different lengths. Yeast breaks down certain sugar chains to alcohol better than others.

With all of that lets say that one day I want to leave the house for 3-4 hours while mashing. My target mash temp is 155. My temp after returning home prior to mashout is about 152.5 due to heat loss from the cooler (a 2.5 degree difference from my target).

Since I started the mash at 155 degrees and after about 30 minutes the temp would still be very close to that, are the sugars that have already been converted at that temp still capable of more conversion at lower temps past the 30 minute point? In other words, does it matter what my initial temp was for the first 30 minutes if after 4 hours the temp has dropped considerably? After sugars are converted at a higher temp, will they continue to be converted as the temp drops? Should I expect my FG to be on the target of a 155 degree mash or a 152.5 degree mash? If I need to leave for a considerable amount of time while mashing should I compensate for heat loss with a higher strike temp?

Hopefully I worded this correctly.

Thanks!
 

However you make beer is up to you, if you have to go out while mashing then so be it, but  your brew may reflect that in consistency.

If you want consistent and repeatable results, I find that it is best to keep the temperature at one set point for saccarification; unless doing a multiple step mash. (I do a decoction step mash for hefe weissbier that uses two sacc temp steps(plus boiling the decoction) but the temp is controlled exactly for each step.)  Otherwise you will end up with a unknown mixture of the two temps, each one creating different length sugar molecule strands,  and although your beer comes out good, you will never be able to repeat it exactly should you want to. Body, mouth feel  and ABV may differ somewhat.

If repeatability isn't an issue for you, go for it. For me,  I want to create great beer but with accurately followed steps and recorded data so that next year I can duplicate it exactly.Years ago I  made many great beers that I didn't follow steps too closely.  I have tried to make them again but can't, ending up with something a bit different; although still quite good, due to inaccurate step temperatures. For a great read, google "The science of step mashing"

If you aspire to become a craft brewer you must strive to be as consistent as you can be. Your best house ale can't taste different every time you brew. You need to be able to reproduce the exact same brew everytime you make it or your brew will lose followers  very fast. CHEERS!

rimondi12 said:

are the sugars that have already been converted at that temp still capable of more conversion at lower temps past the 30 minute point?

Click to expand...

Mash enzymes have finite time spans. Beta Amylase has a half life of 20 to 30 minutes. Alpha Amylase is  hours.  This doesn't mean they stop in that time, just weaken by half for each doubling of that time. OTOH, enzymes stop when they can't access substrate to convert.

What can take over are other mechanical and biological issues, that can break down the mash. Part of this is planned, because that's how starches are extracted. But you may see artifacts that tell you more proteins and glucans are released.

Biologically, it's possible for some flora to break down wort and becomes increasingly more likely with time. For a few hours, I wouldn't sweat it, though. I've had mashes stalled for 6 to 12 hours without any issues that would cause a batch dump. I've had one stall for 24+ hours that had to be dumped.

Thank you for the responses! So to summarize:

Varying temperature in longer mashes (so long as it is only a small variance) will not have a significant impact on the quality of a good beer, but it will affect the beers consistency from batch to batch.

and

Enzymes will continue to convert over longer mashes, however after about 30min to an hour their conversion rates drop significantly. Keeping them in contact with substrate is more important than mash time and slight temperature variances over that time.

Does that sound right?

I actually put this to the test over the weekend due to time constraints:
-Mashed in Sunday evening
-Sparged Monday morning

Marathon Monday... day drinking!!

-Boiled Monday evening

I was surprised to see that my pre boil gravity hit the nail on the head.  Volume was pretty dead on as well.  Tasted fine. 

I anticipated a bump in efficiency and a bit more grain absorption, but didn't see either.

This was a nice brew schedule because I didn't need a solid 6 hour block of time to get 'er done.  This will not be the last time I break up my brew session.