Why is My Efficiency Low?

[belmontbrew]

I just wrapped up my first partial mash with actual process measurements! The bad news is that it looks like my mash efficiency is 58%.

Here is my grain bill:
1 lb Golden Promise (est. 32 ppg)
0.5 lb Crystal 15 (est. 35 ppg)
0.5 lb Wheat (est. 38 ppg)
Total: 2 lb at 34.25 ppg

I mashed in 3 quarts of water, then sparged for a total of 2.625 gallons total volume.

Max gravity = 34.25 * 2 / 2.625 = 1.026
Brix reading = 3.8º, converted to 1.015

Efficiency = 15 / 26 = 58%.

I heated the mash water to 167ºF, dough in and hit a mash temp of 155ºF. My mash was a mini brew-in-bag, with all the grains in a nylon mesh bag. The grains were pretty loose, and I stirred them around 3 times during a 45 minute mash. At the end, the temperature had dropped to 152ºF. I think transferred the grain bag into my boil kettle, where 2.5 gallons of water had just hit 170ºF. I swished it around for a bit, let it drain, and tasted the spent grains. Not sweet. I also roughly measured my water absorption at 0.5 pints per pound.

The water was regular tap, no Burtonizing or other fancy stuff. No protein rest, etc.

So... Anyone know what I can try next time to get my efficiency a little higher? I'd be happy with 70%.

Thanks!

 

[Pommy]

I think the problem may be the diastatic power, from memory golden promise is only around 70 and unmalted wheat and crystal have no diastatic power. Normally you would want at least 50-60 averaged over the total grain bill to allow for propper conversion to take place. I am guessing that the golden promise converted and got some of the crystal and wheat to convert but not enough. The solution would be to use more base grain to up the enzyme levels to convert the starches of the other grains. Of course I could be completely wrong so I'd wait for someone to back me up before taking my word for it.

 

[ajf]

From the 38 ppg for the wheat, I'm guessing that was wheat malt.
If it wasn't malted, then I doubt the golden promise would have enough diastatic power to convert it.
If it was malted, it wouldn't be a diastatic power problem as the crystal is already converted.
32 ppg seems a bit low for golden promise. I would expect about 37 ppg.
You say you transferred the grain bag to the kettle? I thought the whole point of BIAB was that you mashed in the kettle. If you did mash in another vessel, what did you do with the wort that was in that other vessel? It should be added to the kettle.
I'd also think you need to stir really well, rather than just swishing around a bit.
I'm puzzled by your water absorption of 0.5 pints per lb. If you had 20 pints in the kettle, used an additional 6 pints sparge water, and ended up with 21 pints total volume, then you would have lost 5 pints to absorption which is 2.5 pints / lb (which seems a lot to me).
Hope this helps.

-a.

 

[belmontbrew]

The water absorption was based on 3 quarts into my mash tun, and 2.5 quarts out of my mash tun and into my kettle. I used a separate small pot for mash so I'd have better heat retention. After the mash was done, I moved the grain bag to batch sparge in the kettle with 2 gallons. Then I poured the wort from the small mash tun into the kettle for 2.625 gallons total.

 

[belmontbrew]

Oh, and the wheat is wheat malt, so it was supposed to convert itself.

 

[ajf]

OK, that all makes sense except for the absorption of 0.5 pints per lb. I get ~ 1 pint per lb, but you may get a bit better than that with BIAB if you drain the bag.
The only think I can think of that could improve efficiency is not stirring enough when doing the "sparge".

-a.

 

[belmontbrew]

I was thinking about the sparge. One thing I haven't been able to find is a rough breakdown of gravity contribution for the mash and sparge. For example, would I get 50% of the solids from the mash, and the rest from the sparge? I had assumed it was more like 70/30, and that sparging was just to get from Good to Great efficiency.