Potential reasons for undershooting gravity
Potential reasons for undershooting gravity
Hi!
I noticed that I don't get anywhere close to the gravity Brewfather estimates for a given recipe. Latest example is a SMASH IPA with a good 5 kg of pilsner malt that, which on my BrewZilla Gen 4 should have landed me somewhere around 1.054 pre boil. Everything went according to the recipe: 71 °C strike water, 64 °C mash for one hour (even a tad longer than that due to being interrupted by having kids), nice recirculation all along, no visible dough nests. What I got though was a pre boil gravity of 1.037 (forgot to test for starch being still present with iodine though).
This is only my fourth brew on the system, the first I forgot to measure and two were rather experimental, but I am still noticing a pattern here in that my efficiency is rather consistently sub par. I now wonder where to find room for improvement. For me, there's no need to squeeze every last bit of sugar out of my grains, yet at a mash efficiency of only 54% where in theory I might even get 80% does not only strike me as unnecessary wasteful, this way I don't know if I could even make anything bigger than an IPA at all without stretching the limits of my system.
My grain milling is one of the things that I suspect might contribute. So much so that I already wish I hadn't bought a three roller mill but one that I can adjust with simple advice from the internet, it seems everything in this field is geared towards two roller mills.
Also I started thinking about pH. Until now I never tampered with it, does it really have the potential to make such a huge difference?
All other suggestions are welcome as well. Cheers!
Low brewhouse efficiency can be a bear to troubleshoot. Usually they're procedural problems. Tweaking the chemistry gets you a few points but if you're off 10% or more off your target efficiency, it's usually something else.
One of the things that can hit your efficiency numbers is a stuck sparge, or channeling in the mash tun. Sparge water finds the path of least resistance to the spigot, so if the grain bed is uneven, the sparge water will bypass the denser inclusions and leave sugar on the table, sort of like a stream cutting a channel in the mud.
Your grind might be contributing to that situation if it's too fine, and you have too much flour in the mix. You need to stir it really well after strike, and then let it settle. If you can adjust anything on your mill to reduce flour that will certainly help. Otherwise adding rice hulls to the mash help to even out the consistency of the grain bed.
One trick I used to use would be to give everything one last stir at the end of the mash, and then pull a couple liters of wort to gently pour back on top. Is repeat the process into the wort ran clear. This would help to even the grain bed and then help it settle.
Other contributing factors could be how fast you sparge. Too fast and you're not going to capture all the sugars. Slower is generally better, since it gives the fresh water time to dissolve any extra sugars left in the grain. It also helps to reduce channeling.
My typical efficiency was 75%, maybe 80% on a very good day, but I tried to remind myself that chasing efficiency only got you frustrated.
Hope any of this helps!
I absolutely agree that going for perfection is a recipe for unhappiness. It’s only that I’d like to remotely get into the ball park of a recipe. At the moment, I’m so far off that I wouldn’t even dare to try Belgian beers, strong stouts/porters or anything like that, just because I wouldn’t know how to fit enough grain in my mash tun should I try to correct for the low efficiency.
That said: As I also like coffee, I’m aware of how challenging works. I believe I stirred seriously, but you never know. Other than that my recirculation was not continuous, instead I set the pump to 60% - which turns it off 40% of the time, allowing for some backwards flow to happen. This is often enough to free the pump if it’s blocked, so I hoped it would help agitate the grain bed in a way that prevents channels from forming. Again, you never know.
If anybody reading this who also uses an AIO-system like BrewZilla, Grainfather and such and might care to share photos of their grain crush, that might also help me.
Did you sparge the grain when you were done mashing?
Oh yes, I totally forgot to mention that: 19 litres of strike water, 10 litres of sparge water, warm/hot-ish.
My FIL often has efficiency issues with his AiO system and a friend of mine had similar issues to the point where he built himself a cooler mash tun to use with his. I don't know what the issue is, but you can pretty easily solve it by purchasing an extra pound of base malt for a few bucks. At the homebrew scale this isn't breaking the bank (like it would be a commercial brewery making 100s of bbls).
Why are you heating your strike water to 71C? is it enough when adding room temp grain to cool down to your target mash (I wonder if you're not accidentally destroying some enzymes)? What about the age of the grain? Enzymatic activity drops the longer grain is stored. Maybe you got a very old batch?
Using and AIO system, it should have the ability to control temp during the mash. I use one myself and a general all rounder mash program would be this: add the grain at around 45-54 C, then let it ramp up to 63. Hold for about an hour, ramp to 72, hold 10-30 minutes and then mash out at 78. Sparge at 78. I'd rather start too cold than too hot. Plus, there's some other enzymes in there that work at low temps but get denatured at 63+ (like proteases and beta-glucanases).
71 °C is the temperature that will drop down to 67 when adding the room temperature grains, yes. The grains are also fresh, I bought them only a couple of months ago and stored them in air tight buckets with click- or screw on-lids ever since.
I know about the purpose of a step mash and my last two brew days involved them, yet without benefit. What I picked though up is that given today's grains, starting the mash as low as 50 might even be detrimental to the head retention as the proteases might eat away more protein than required. But on this, I'm only reciting theory learned elsewhere and can't speak from experience.
I just read comments here for the last few days. But what I would try is start lower, the 78°C temperature denaturates alpha and beta amylase, you are well under that temperature but guy from brewing institute here suggested to me few years ago that 64°C is optimal for malts nowadays (in home setups).
Other than that as suggested in other comments check flow and your malt crushing.
Iodine test may point you in right direction, it may occur in sparge - negative starch test, or before that - positive starch test before sparge.