Why is my mash efficiency so much higher with a decoction mash?

[shanecb]

When I brew a beer with a large percentage of wheat malt (hefeweizens most often), I usually only get about a 60% mash efficiency with a single infusion mash. However, when I do a double decoction mash schedule my efficiency jumps way up to 91-93%. What exactly is the mechanism that gives me such a big jump in efficiency? When I do a decoction I actually hold at saccharification shorter than I do for a single infusion (35min or so versus 60min).

Could it just be the fact that the wheat is soaking for so much longer during a decoction, pulling out more starch? If so would an extended single infusion mash increase my efficiency some?

 

[wobdee]

From what I've read I think higher efficiencies are obtained in a decoction because boiling the mash breaks down a little more starch than a standard mash. The longer overall mash times probably help as well.

 

[shanecb]

I didn't consider the boiling, but that very well could be what is happening.