Need help diagnosing efficiency on a wheat beer

Question

Yesterday I did my 12th brew. My third in my current equipment setup. All-Grain BIAB where my efficiency has been consistently over %70. My previous brew, an IPA I hit all my numbers. I changed no variables for this beer except of course the recipe. I striked at 158F, mashed for 90 minutes at 153F (stirred many times). My one gallon recipe:

• 1.5lb White Wheat Malt

• 0.5lb Pilsen

  60 min boil on .2oz Tettnang.

Post mash, I lost .125 gallons of water as expected (left with 2 gallons in pot). Hit a pre-boil gravity of 1.022. Was expecting 1.027. I guess that doesn't seem huge, but come end of boil I had .1 gallons of trub and 1 gallon of wort, which measured in at 1.035. Any ideas as to what would have led to numbers like this? And what steps should I take in the future to ensure better numbers? I ask about the white wheat in particular because it is the only ingredient I have not used in a mash before (link to malt)

Answer 1

Best guess I can venture is that the wheat was milled too coarsely to allow for good solubilization and conversion of the starch with your equipment set. In my experience, wheat malt tends to be less friable than barley malt (as in: the endosperm, where all the starch is, doesn't break down to sufficiently small particles quite as easily). With BIAB, where you don't have to worry about lautering, you can mill quite fine to get better extract efficiency, and a less-than-ideal grind coupled with the already-low efficiencies you tend to see with BIAB may have led to your low extract.

Another, less likely option could be insufficient starch conversion. Though most wheat malts have very good diastatic power (meaning they have enough endogenous enzymes to convert their own starch to fermentable sugars when mashed), I have heard of wheat malts having lower diastatic power. Unfortunately I can't figure from the link provided whose wheat malt it is you're using, so that's really a shot in the dark. But if it did happen to be a poor self-converter, the wheat malt in such a high proportion could have caused this.