Really poor efficiency: why?

I use the BIAB method. Typically I get around 65% efficiency. Yesterday, though, I brewed a batch and measured about 45%; got an OG of 1.050 when I was expecting 1.060. I'll lay out the recipe below. So, here's my question: my mash temp was a bit warmer than I wanted; it was about 154 degrees, for 90 minutes. Could that have contributed? The only other thing I can think of is that I took the gravity reading after aeration; usually I take it before.

So, here's the recipe:

Maris Otter: 10 lbs
Victory malt: 1 lb
Crystal 60: 1 lb
Northdown 7.2%: 90 min
UK Challenger 8.3%: 45 min
UK Challenger 8.3%: 10 min

Strike water was 7.3 gallons at 168. Mash was 90 minutes at 152 (actually around 154). No active sparge.

Boil was 90 minutes. I expected 5.25 gallon in the fermenter. I got 3.8. No idea why.

Thoughts?

Temp will not affect efficiency as long as it is in the proper range, which yours was. Could be your mash pH. Could be the crush on the grains. Anything possibly different with either of those?

double check the thermometer. Sparging is good for efficiency, it goes without saying.

Northcalais40 said:

double check the thermometer. Sparging is good for efficiency, it goes without saying.

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I assume the OP's process was his normal process, so the amount of sparging (or lack thereof) doesn't explain his drop in efficiency. Also, his OG was lower than expected. If he didn't sparge, his OG should be higher than expected.

Correct; my process was as per my usual. My grains were crushed by the same local store from which I always get them. Ph, however, I must say I don't know about. That's not a measurement I usually take.

mcduhamel said:

Correct; my process was as per my usual. My grains were crushed by the same local store from which I always get them. Ph, however, I must say I don't know about. That's not a measurement I usually take.

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The store's crusher may have a wider gap this time than previous due to wear or someone adjusting it for their system. The quality of the crush is the biggest factor in the efficiency of the mash. If you do a reasonable amount of brewing you should think about getting your own grain mill, be it a roller mill or a Corona style grinder. That way you have more control on the crush and the attendant efficiency.

I think there's a problem with your water volumes. I also BIAB and with 12 lbs of grain you should have only lost about a gallon of water to absorption. If you started with 7.3 gallons for strike water you should have ended with roughly 6.3 gallons before boil. With a loss of 1.5 gallons at boil you should have ended with about 4.8 after boil. If you got a 1.050 your efficiency is about 55%. Check your volumes, if you were light with your strike water or your crush was too big your efficiency will suffer.

I double crush my grains, mash in at 153 and I get 77% pretty consistently.

mcduhamel said:

Correct; my process was as per my usual. My grains were crushed by the same local store from which I always get them. Ph, however, I must say I don't know about. That's not a measurement I usually take.

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For pH:
Did you use the same water? Have you made this recipe before? If you have hard water, you might not have dropped the mash pH down enough. Too high a pH will result in poor enzyme activity, which could impact your efficiency.

The question basically comes down to whether the low efficiency is coming from low extraction or low conversion. An iodine test would help figure it out (in the future). If you have poor conversion due to improper mash pH, your wort will have a lot of starch in solution and you will get a positive iodine test. If the problem is poor extraction (because of a poor crush), the iodine test will be negative, indicating all the starch has been converted into sugars.

Again, I would suggest double checking the accuracy of your thermometer.

Northcalais40 said:

Again, I would suggest double checking the accuracy of your thermometer.

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My thermometer or my hydrometer?

If your efficiency was low and you ended up with less volume maybe for whatever reason you didn't get all the sweet liquid out of the grains when you pulled them out. Maybe it cooled down too much and started to gelatinize before you were able to squeeze the liquid out or couldn't get it out for some other reason.

Just a thought. I've only done BIAB once so I'm no expert.

I have to say that water volume was likely your problem. If you ended up with 1.45 gallons less than what was anticipated, then you left behing a bunch of sugar that would have been dissolved by the extra water. And you obviously didn't boil off more water than usual, or your OG would have been high, not low. Next time be more careful with your water measurements, measure your runoff before you boil, and if you are short on your boil volume, sparge until you get there.

BBL_Brewer said:

I have to say that water volume was likely your problem. If you ended up with 1.45 gallons less than what was anticipated, then you left behing a bunch of sugar that would have been dissolved by the extra water. And you obviously didn't boil off more water than usual, or your OG would have been high, not low. Next time be more careful with your water measurements, measure your runoff before you boil, and if you are short on your boil volume, sparge until you get there.

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Thanks. Makes sense, although generally I don't sparge with my BIAB method.