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Mash tun temp - when should I start to worry

Doing my second mini-mash in a 10 gal rubbermaid cooler. Temp was 152 when I closed the lid, and has fallen to 145 in 15 minutes. At what point should I start adding boiling water to bring the temp up?

Water to grist ration if 1.5 quarts per pound grain.

Don’t worry, but increase the temp to 168F NOW with additions of boiling water. It sounds as though you found out the hard way that 10 gallon round coolers lose 8f if not pre-warmed. In the future just account for at least a 8f loss. The 145f will make a more fermentable wort, SO the 168f will stop all/ most conversion. The 145f makes a drier tasting wort in the end (IE: more fermentable is all), but not thin hopefully dont worry about the mash being done, by the time you raise it now you will have mashed for over 30 minutes at least. I wish to know more of your procedure when you find time as its kind of rare to do a mini mash in such a large container. Your probably just using it until you go full blown AG I’m guessing. But the reality is you might as well just start doing AG if you have a boil kettle and burner, chiller that can handle it.

Anyway what amount of water and grain do you have now and what is the current temp, I can tell you what infusion you will need of boiling water if you dont have a calculator for it.

Conversion goes pretty slow and is relatively inefficient at 145°F. If the mash has been at 145°F for 30’, I would raise the temperature to 158-162°F, not 168°F. This will allow conversion to complete and additional conversion will have lower fermentability and come out, on average, similar to what you might have expected at 152°F. 168°F would come close to stopping conversion by denaturing the enzymes, and 30’ in would be too early at 145°F.

If most conversion is actually done in 15-30minutes Sloth. Why have him do any rest at 158-162? he is far past the useability of this rest if he sat 30-60 minutes under 150? So to direct a halt of conversion is the most prudent choice wouldn’t you agree? Why continue to mash for 2 hours whats your theroy here? I would think you extend out the fermentibility even further.

I also say the “30 is to early” comment is misstated at best as he will also continue to convert thoughout sparge if not halted creating a super thin mouthfeel if not halted. It seems that the trend lately is to mash for 100 minutes. Entirely unnecessary I see full conversion within 15-30 minutes. And I dont see why homebrewers expect that they need to mash 90-100 minutes when its well established within commercial circles that conversion can/ will complete within 10 minutes if optimal. Now with a suboptimal PH etc… Maybe 30-40.

I thought a simple and sweet approach was best with a brand new brewer but it seems we need to go into tit-for-tat aspects that he should not be worrying about quite yet.
Here is a good set of quotes from pro brewers that shall serve to feed into my feeling around this matter and it is best that we start a new thread if needed as this OPs question did not need to goto into a conversation about step mashing. IE: 144 for 10-15 then 158 for 10-15 then move onto mashout in needed.
“60 minutes is a very long conversion rest. The goal of the conversion rest is to suficiently break down the starch to get your desired wort carbohydrate profile, and to move along as soon as possible. There are deleterious effects of long conversion rests”
“think about extracting lipids and polyphenols from malted barley husk. Long term stability and flavor (astringency) issues”

I’m sure we’re well past being of any further use to the OP, but the discussion may prove useful to brewer’s trying to understand the mashing process so that they can make their own decisions about mash temperatures.[quote=“ITsPossible”]If most conversion is actually done in 15-30minutes Sloth. Why have him do any rest at 158-162?[/quote]
My experience is that, among homebrewers, conversion is complete in 15-30 minutes only in exceptional cases. Even after 1 hour, if the wort never reaches the high 150’s, there is often 10-20% of the starch left unconverted unless the grist is very finely ground. This is one of the reasons that so many brewers see mash efficiencies in the 65-75% range when the predicted efficiency would be closer to 85-90%.

The wort may test negative by iodine, but if you check the conversion efficiency by the wort gravity, you’ll find that there is often plenty of starch left in the grist to convert, particularly at 145°F, where starch gelatinization is poor. However, this mash didn’t start at 145°F, though, so there is probably a lot more conversion than one would see in a typical mash that has remained at 145°F.

If he raised the mash to the 158-162°F range, conversion would continue, but the additional wort produced should be of a lower fermentability. I was concerned that the OP was risking getting a low OG by terminating the mash early with a mashout at 30 minutes, but seeing that he was doing a mini-mash, a low OG could be made up for with DME and a more fermentable wort is probably desirable to make up for the lower fermentablity of the extract.

Just after posting I boiled some water and added 1.5 quarts to the mash tun, which raised the temp to 154 according to the thermometer I was using to monitor temp. I should have confirmed the temp with a second thermometer before adding the boiled water, because I found out later the temp readings were off by ~10 degrees–or more depending on where I tested in the grain bed. So if anything, I was mashing too warm for much of the hour and will end up with a sweeter, less fermentable wort as I understand it. Good thing I have the DME/LME as a safety net. I’m extra eager to see what the FG will be. I ended up 9 points under my target OG according to Beersmith, but that’s OK because I was aiming above the upper limit for the style anyway.

I pre-heated the cooler before adding the strike water. I suspect the sharp temp drop was not real, but I have no way of proving it. I found that the probe was not actually in the grain bed. It was in the 1" of water above the grain bed. My theory is that this water is somewhat of a barrier between the grain bed and the dead space, and is therefore more susceptible to temp loss than the grain bed itself. This is probably more true in my mini-mash set up, because of the huge amount of dead space.

Yeah, I plan to go all-grain soon and am using the larger cooler to practice the procedure with lower risk to the final product. I guess I could just keep some DME on hand in case I have problems with an AG batch.

Conversion is not done that quickly at lower temps.

Commercial breweries may take an hour to mash in and an hour to sparge, all at mash temps, in addition to the rest. Comparing commercial practices to homebrew practices is not always a good comparison. For example, if you batch sparge, the sparge is going to take more like 15 min. than an hour. As to why longer mashes, it’s to control the fermentability of the beer. I have seen definite difference in beers mashed for 60 min. and those mashed for 90. If it doesn’t make a difference to you,cool. But for some of us, it does.

15 minutes to batch sparge? Interesting. I’ve never found a thorough description of batch sparging procedures, so I’ve just assumed I should refill the cooler with the same amount of water and let it rest for the same amount of time I would if I were using a sparge arm (I think I’ve read somewhere that the sparge should take the same amount of time as your mash) and then drain slowly.

Can you explain the rationale behind the 15 minute batch sparge? Is it that you’ve already done all necessary conversion during the 60-90 minute mash and you only need to rinse the grains to extract any sugars clinging to the grain, so there is no real benefit to a longer rest during batch sparge?

[quote=“kcbeersnob”]15 minutes to batch sparge? Interesting. I’ve never found a thorough description of batch sparging procedures, so I’ve just assumed I should refill the cooler with the same amount of water and let it rest for the same amount of time I would if I were using a sparge arm (I think I’ve read somewhere that the sparge should take the same amount of time as your mash) and then drain slowly.

Can you explain the rationale behind the 15 minute batch sparge? Is it that you’ve already done all necessary conversion during the 60-90 minute mash and you only need to rinse the grains to extract any sugars clinging to the grain, so there is no real benefit to a longer rest during batch sparge?[/quote]

In fly sparging, you rinse the grain. In batch sparging, you get the sugar into solution and drain it out, so it’s much faster. In addition, since you’re not continually diluting the buffering power of the grain, pH of the sparge is almost never an issue in batch sparging. For a 7.5 gal. boil volume, I vorlauf, drain the mash, stir in the sparge water, vorlauf again and run off the sparge all in 15 min. For details, take a look at dennybrew.com . I get an average 85% efficiency. I’ve done this for 411 batches and it works so well I have no desire to do anything else.

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