Big beer efficiency and fermentation question

Brewing Processes
1

Having problems hitting efficiency and SG targets consistently with big beers. AG brew 5 gal batches with 8 gal pot, 10 gal MT and batch sparge. Know efficiency will drop with big beers. Wondering if as a general rule increasing the mash from 60 to 90 min and increasing the sparge from 30 to 45 min will increase efficiency without adding off flavors. Know SG can be increased with DME but would like to try longer mash / sparge times first.

Typically ferment in primary for 14 days and in secondary for 7 days, both at 68 F. Just started making a yeast starter. Thinking of increasing primary to 21 days, especially for big beers but wondering if the longer primary time is needed with a yeast starter.

2

There’s no way to say without knowing what your typical conversion efficiency would be for a 60 min mash.

With normal pitching rates, a good rule of thumb is ~2°P (eight points) of attenuation per day. So even a really big beer should reach FG in about 10 days. I’d still leave it on the yeast for at least a few days though, depending on how it tastes at that point.

3

Extending the mash time won’t help at all.  The thing you really need to consider for big beers is whether to sparge more, and thusly boil more.  For a big beer I will often boil for 2 to 2.5 hours, and sparge enough to account for the longer boil time.  Then you can still get your efficiency in the 70s or maybe even 80s.

As for fermentation time, don’t rush it.  The yeast will tell you when they are done.  As a general rule, I’d give it a good 3 to 4 weeks before even thinking about secondary or bottling/kegging, and even then, check your gravity every few days to see if it is still changing.  Warming the beer up near the final gravity is also a great idea.  Even for lagers, you can safely take the beer up into the upper 60s at the end of the fermentation without ill effect to help the yeast finish up their job.

4

So many things affect efficiency it is hard to say. A 60 minute sach rest is plenty. Increasing sparge time may help. Also look at your grain crush, mash pH, and filter. Step mashing may help. Water to grain ratio makes a difference too.

5

You don’t say whether you fly sparge or or batch sparge, but if you batch sparge a longer sparge won’t make any difference.

6

He batch sparges, which is why I was confused on how a longer time spent sparging would increase efficiency.

At any rate, the main factors for increasing my efficiency (even on 1.070+ beers) was a tighter crush (thanks Denny!) and a thinner mash. I mash nearly everything at 2 qts/lb if my 10 gallon mash tun can hold it.

7

Another strategy you might want to consider is to simply alter your efficiency targets for your big beers rather than chasing a bunch of possible tweaks/fixes.  As long as you’re consistent, even it is lower, you’ll be able to calculate and hit your volume/gravity targets just fine.

8

With either method, it would increase efficiency if conversion isn’t complete at the end of the mash rest.

9

I find conversion is done in 15-20 minutes, and certainly within an hour.  Mash time is not a factor in my experience.  YMMV?

10

True. I was making a quick assumption that conversion was complete after 60 minutes.

11

Stirred mash, maybe? I generally find that I’m at 85-95% when I start vorlauf (45 min), and 95-100% after (60 min).

12

My thinking is mashing for 60 min allows for conversion. Mashing longer should increase conversion, assuming conversion is not done in 60 min. Same for batch sparging (draining MT, add sparge water and let sit 30 min) Increasing sparge time to 45 min should increase efficiency. I sense that is incorrect but don’t know why. JUST SAW THAT CONVERSION IS DONE IN 20 MIN. WHY DO MOST RECIPES CALL FOR 60 MIN MASH, 90 MIN FOR BIG BEERS? I STIR MASH AND SPARGE SEVERAL TIMES, RECIRCULATING WITH 2 - 4 QUARTS BEFORE DRAINING.

Am limited to 9 gal total water. Currently put 5 in mash and 4 in sparge. Equipment and boil off loses gives 5.5 gal to ferment and 5 gal to bottle. Maybe it would be better to max out the water in the mash and use the rest for sparge, keeping total at 9 gal. May have to add DME to hit SG.

Just got grain mill and have only used it once, crushing at .039. Can tighten the crush but to what? Any suggestions? Efficiency was about 60%.

Another web site posting recommends leaving imperial stout and barley wines, which is what I make, in the primary for about a month. It also recommended to bottle condition for 3-4 months. Any thoughts?

Have never measured pH. What is a good but inexpensive way to measure it? What are good pH numbers?

Am thinking the advice to focus on CONSISTENT efficiencies, even if they are lower, then calculate and hit your volume/gravity targets just fine means to get as much efficiency from your system as possible, and do it consistently, then adjust volume / SG with water / DME as needed, correct? That works and given equipment limits may have to do that.

13

I rarely find that conversion is complete after 30 min. It also depends on how you measure it. an iodine test may be negative at that time but the mash gravity test may show that not all the starches have been converted yet.

ImperialStout, oftentimes it’s the lower efficiencies  that are fluctuating from batch to batch. There is a similar thread going on in parallel. http://www.homebrewersassociation.org/forum/index.php?topic=14505.0

Kai

14

I find that for a given volume recipe (e.g., 5 gallons), assuming all other variables remain the same (e.g., crush, pH, mash temperature, etc.), brewhouse efficiency is inversely proportional to the intended original gravity or weight of grain used.  You will not get consistent efficiency unless/until you aim to brew a consistent gravity beer.

My experiments have also proven to me, on my system, that if I mash for 20 minutes or 40 minutes or 60 minutes, it makes zero difference in efficiency.  Mash time is a limitation that you might need to figure out for your own system to see what you can get away with.  I think the reasons for the 60-minute rule of thumb is that 1) it will work on all systems, as well as 2) general American laziness and preference for nice round numbers, e.g., you can specify “mash for about 1 hour” versus “mash for at least 0.67 hours”.

Furthermore, the reason we don’t just mash for 15-20 minutes, even if conversion is “good enough” at that point, is that the sugars that have been generated through enzymatic action at that point are still fairly complex ones and need more breaking down to improve fermentability.  For example, it does no good to get 90% efficiency after just 15 minutes mash time if your OG=1.060 beer can only ferment down to FG=1.030 because many of the sugars are too much for the yeast to handle.  So, while you may have a good sweet wort after just a few minutes, it’s not something you’ll enjoy drinking at the end of fermentation.  So we mash for 60 minutes (or me, I mash for 40) so that we can get down to that FG=1.015 that we want for an easier drinking brew.

I do hope Kai corrects me where I’m scientifically off base.  All I can do is share what I’ve learned through experimentation and experience, in the hopes that it will help someone out there to be a more critical thinker such as we are.

By the way, a good pH number at mash temperature is about 5.2 to 5.5, with 5.3 being the “ideal”.  This can be measured with a fancy chemical gauge, or you can use the cheap pH paper.  Adjustments can be made with the different brewing salts or with acidulated malt, etc.  For most water and most styles, your pH will naturally fall pretty close to this range on its own without added stuff.  But if your water isn’t great then it might do strange things to your efficiency.  Most of us don’t worry too much and are actually fine in not worrying.  But it is worth finding out what your typical pH is anyway, if nothing else just to rule it out as a possibility.

You can tighten your crush as much as you want, the limiting factor being the dreaded stuck sparge.  I brewed for years using my friggin blender to “crush” the malt, and made many award-winners that way.  The stuff you might read about tannin extraction is largely blown out of proportion and is primarily an issue for fly spargers who sparge too much, not batch spargers and certainly not for batch spargers of big beers where the pH and gravity are very unlikely to reach the limits to where tannins get pulled out.

How’s that for a data dump!

15

No, you are not off base. I never said that its impossible. The point I’m trying to make, and that is not directed at you Dave, is that many brewers jump to the conclusion that they can mash much shorter than 60 min just b/c some malt analysis tests can get the malt to convert in 15 min.

Maybe my crush is not tight enough, but very often I see that I gain another 5 points in conversion efficiency if I mash longer than 60 min. In most cases I’m counting on that. The time the mash is resting doesn’t bother me much since I can do other things during that time.

Kai

16

Thanks, Kai.  I see what you are saying.  You, and many brewers, may desire a gain of 5% efficiency.  Perhaps what I don’t realize is that for me, efficiency doesn’t matter at all since I already see brewhouse efficiencies in the mid-80s or even 90s for my small batches mashed for 40 minutes, to where there is truly not much left to be gained by mashing any longer.  Plus, for me, with a wife and 3 small kids to attend to, I like my brew day to be as short as humanly possible.  I can knock out a small batch in 3.5 to 4 hours, versus the 5 or 6 hours it might take to do 5 or 6 gallons.  So it does seem the answers are different for each brewer, depending on their batch size and system.  Interesting.  I guess I never really thought about this.

17

Definitely varies, Dave, as we’ve discussed before.  It’s totally subjective, but I find lighter body and increased fermentability from longer mashes.

18

If I’m not getting close enough to my expected efficiency I’ll have to boil off more and I want to avoid that.

[quote]Plus, for me, with a wife and 3 small kids to attend to, I like my brew day to be as short as humanly possible.  I can knock out a small batch in 3.5 to 4 hours, versus the 5 or 6 hours it might take to do 5 or 6 gallons.

[/quote]

I hear you just to well on that one. In my case longer mash rests can give me more time to help around the house. I have made a few beers in the past where I timed mash rests and boiling with preparing and eating dinner and putting the kids to bed, respectively. In that case long mashes do help.

Kai

19

I think the 9 gallon water limit is the key because you are bumping into the maximum gravity that you can get from your first runnings.  I have rarely seen my first runnings exceed a gravity of 1.080.  Even with huge grain bills, the gravity drops off from that starting number and if you have 9 gallons in your kettle at 1.060, that will boil down to 5.5 gallons at 1.098.  There is still a lot of sugar available in the mash, it is just getting thrown away.

One way to increase your water limit would be to bring 3 gallons up to a boil during the mash and put it in a corny keg.  It would then cool down to sparging temp by the time you need it and you could use a cobra tap and CO2 to push it into the mash tun.

Since your boil kettle is maxed out, you could collect those runnings in a bucket.  Those runnings could be added to the kettle slowly during the boil.  Using this method, if you can collect 12 gallons at an average of 1.055, that will boil down to 5.5 gallons at 1.120.  I think you’ll find that an extended boil works really well with big beers.

20

why do you say you are limited to 9 gallons total water? you say you have an 8 gallon pot with a 10 gallon HLT. That right there says you could have 18 gallons of water ready for mashing/spargeing.

try mashing at 2 qt/lb then spargeing with as much additional water as you can fit in your kettle after. with a big 20lb+ grain bill you are going to lose close to 3 gallons of water to the grain so…

20 lb grain @ 2 qt/lb = 10 gallons mash water with ~7.5 coming back out. put 2 gallons of those first runnings in a big kitchen pot on the kitchen stove and boil till yer scared as they say. reduce it down to say 2 qt or 1 qt even, syrup.

then sparge to the limit of you boil kettle maybe another 2 gallons. you would have to baby sit the boil for a while until it evaporated a couple qt but…

Now, with the remaining hot sparge water, sparge again into a third pot or bucket, just a gallon or two, and put that into mason jars pressure canned for starters later!