Low Efficiency & High Attenuation

[Gavagai]

Since going all-grain, I've been consistently seeing very low efficiency (sub 70% with a single batch sparge), and very high attenuation (85%+ AA in all malt worts with a 60 minute 150-153F saccarification rest). I've tried crushing finer and finer, even going below a 0.020" mill gap.

I'm thinking that my issue may be with mash pH. I've been using ColorpHast strips to measure pH, aiming for a reading of 5.0 - 5.2 at mash temp, but it's pretty hard to read the strips accurately. According to Greg Noonan, alpha amylase has an optimum pH of 5.7, while beta amylase has an optimum pH of 4.7. Could a low mash pH be favoring beta amylase over alpha amylase, resulting in poor starch conversion and a low-dextrin wort?

 

[pvtschultz]

Before you get too wound up with mash pH, I would make sure that your measuring equipment is accurate. My beers always tasted dry and overly bitter when compared to Mash temp and FG. Ended up finding out that my hydrometer reads four points high and my thermometer read several degrees low. My personal opinion is that some people worry too much about pH and not enough about proper water chemistry early on. Use good water and accurate instruments first, I like using the Easy Water spreadsheet to calculate additions, and then get more concerned once you have those first bases covered. Just my $0.02.

 

[Gavagai]

My hydrometer reads two points high, which I account for. I use Kaiser's water calculator, though I have some concerns about seasonal variation in my water supply. My water is very low mineral and hence very responsive to pH regulators. I generally add just enough gypsum and CaCl for calcium requirements, which puts me in the right pH range for pale to amber beers. For darker beers, I use CaCl and calcium hydroxide. I have had not had as much trouble with overattenuation in my dark beers, but they also have a lot more specialty malts in them.

I want to buy a pH meter, but am discouraged by how short their lifespan seems to be. Is this the only logical next step?

 

[SpeedYellow]

Are you seeing this low efficiency with a variety of base malts, including malts that previously gave you high efficiency? I find some malt always put me in the low 60s, while others in the mid 70s.

Are you seeing this high attenuation with a variety of yeasts? Obviously attenuation is mainly a yeast issue. And are you outside of the expected range? As you may know, big beers often under attenuate too.

I agree that it's probably not be a pH issue. Plus, if you're getting 5.0-5.2 on colorphast, you're fine. My strips read 0.4-0.5 low on average (I compare to my pH meter every batch, just by curiosity). I've committed much much worse pH sins and still gotten 74% efficiency.

 

[duboman]

I agree it's probably not pH.

Low efficiency of mash/lauter or brewhouse? there's a difference and many variables involved. Details:

Attenuation always being high leads me to believe you are mashing lower than you think. glad to hear your hydrometer is calibrated and you are making the adjustment but just as important is calibrating your thermometer to ensure you are mashing at the temperature you think you are. Consistently high attenuation leads me to believe this is the issue. A few degrees lower can greatly increase the ferment-ability of the wort and increase attenuation of the yeast, regardless of the strain.

BTW, consistency is more important than higher efficiency. If you are always getting, say, 65-70% then just adjust your recipes to match your efficiency instead of chasing higher numbers.

 

[Andrikos]

"Thermometer accuracy" is the first thing that popped into my mind because it explains both your problems in one fell swoop.

Verify/calibrate it with ice water and boiling water and your problems will likely go away.