A couple weeks ago I made an Irish Red. I was supposed to mash at 153 degrees, but I forgot to preheat my mash tun (sitting in my cold garage), and I got busy and didn’t check the temperature while it mashed. After an hour, I opened it and the mash was sitting at 141 degrees. At that point, I didn’t bother to see if it had converted, I just brewed it anyway.
Can anyone predict how it might turn out? I assume it will be very thin bodied, at least, but I wonder if it will even taste remotely alright.
When you mash at a lower temperature the conversion process takes longer and may not complete in the 60 min that most of us give the mash. The result is lower efficiency and possibly unconverted starches that can give the beer a starch haze. If your mash temps are substantially lower (140 and lower) starch doesn’t gelatenize and the conversion process takes much longer since the enzymes have to chew away on the outside of the ungelatenized starch granules. At this point you would have substantially lower efficiency.
Another effect is that enzymes like b-amylase and limit dextrinase survine much longer and are thus able to produce more fermentable sugars. The resulting wort will be more fermentable and the finished beer can end up thin and lacking body.
A couple of online sources I’ve read say that barley starch gelatanizes between 147 and 153 F (64-67 C), but it can vary up to 10°C depending on factors like crush, modification, water to grist ratio, etc. Ungelatanized starch has the consequences that Kai states above. Based on my anecdotal experience of taking mash gravity readings on the last half dozen batches, just about any beer mashed in at or below 152 has not completed conversion in 60 minutes. This is always remedied by raising up above 155 for a very short amount of time, maybe 5 min. I theorize that ungelatinized starch is the main culprit, not sluggish enzyme activity, but either problem has the same solution.
My name is Jeff and I am a low masher…it has been almost a week since my last low temp mash
My normal mash temp is 150F, and I routinely go as low as 146F. I always mash for at least 90 minutes when below 150*, but have never seen an unconverted mash, based on the iodine test. I wonder if this has something to do with the brand/type of grain being used?
Hey Jeff, I just did an overnight mash two nights ago. Mashed at 152F and left it overnight, when I got up it was still just over 100 F. I boiled the wort that morning and left it to cool overnight as well… didn’t use a chiller. This morning when I got up it had a skim of ice on the top. :o :D I had to warm it up to pitch yeast, and I have to say the wort is one of the best tasting worts I’ve made yet. Now I’ll just have to see how it finishes I guess. I’m kinda chomping to try an open ferment too but I’m not that daring with my shed yet.
An iodine test will absolutely check for conversion of starches into sugars. What it won’t tell you is if the starches have been completely extracted from the grains, which may not happen at very low mash temperatures.
The IPA I just made came in almost 10 points lower than I expected and I did mash lower than I wanted, but I also had a high pH in the mash too. I’ve also noticed that when I mash low, I’ve had haze, permanent haze not just chill haze as far as I can tell. So Kai’s reply explained a few things, for me anyway… and it didn’t have a lot of chemistry lingo in it to confuse the hell out of me. :D
To present a different opinion, I recommend doing the iodine test. Especially when trying something new. If you do it on chalk, which is the method recommend, it is very easy to read. Here are some pics: Starch Test - German brewing and more
I’ll have to rewrite this article to take out the method of using a white dish. Denny is correct that those test are difficult to read because of the husks and malt grits that may test positive.
Agreed Kai. An iodine test is proof positive that starches were converted to sugar.
A refractometer can also confirm the presence of sugar in solution as well as precisely measure the %Brix. I believe it’s all about time and temperature. When one follows the recipe protocol there’s no need to test for conversion. It’s time and temperature. All one needs is a calibrated thermometer and a timer. For example, If I mash at 150F for 60 minutes I will get conversion… it’s that simple.
However, when the prescribed mash temp was not met it’s a matter of either increasing the temp or increasing the mash time. As long as the mash temp was > 141F
I had a number of mashes where time, temp and pH were ok but I needed to
take action on a positive iodine test. Granted, these weren’t 2-row mashes but mashes with
lots of dark Munich malt.
Overnight is a long time. I’m assuming conversion happened within the first 60-90 min. Is there benefit to prolonging a mash if conversion is completed?
If there is no harm in an extra long mash then why bother mashing out at 168. why not mash out at 150 or whatever your mash temp was?
Mashing out denatures the enzymes and therefore locks in the ratio of fermentable/unfermentable sugars. If you take a long time to sparge (as in fly sparging) or let the mash sit a long time (as in an overnight mash), then polysaccharides will continue to break down as long as it’s within the effective temperature range. The result being a very attenuative wort.
