I’m definitively in the decoction mashing camp. It is more laborious but it’s also more intuitive to me. For wheat beers this is pretty much a requirement, although people more talented than me have had great results with infusions.
The problem with most texts describing this schedule, is that the examples are for malts which are not well modified and are thus not really applicable for todays modern malts which are highly modified and very suitable for infusion mashing but lesser to the traditional decoction schedules.
One interesting benefit from decoction mashing is that it gives the limit dextrinases the opportunity in further breaking down the products made by the α-amylase during the first decoction. Effectively, it is better for the α-amylase to break down the starches before the β-amylase, but in infusion mashing it’s the other way round and thus the resulting fermentable sugars are less.
To achieve the high attenuation of a reference beer like Augustiner Edelstoff (OG 12.7° P, FG 2.3° P), this seems like the only way to achieve this level of attenuation with the given grain bill (Augustiner does way more to make this product what it is. It’s a very funky method which involves separating the grind into hulls, kernels and flower, treating each differently during the mash – but that’s a different story…)
In his text-book, Ludwig Narziß describes a double decoction schedule which doughs in at 35C in order to encourage the solubility of the enzymes and therefore enhance the conversion into the important sugars.
What follows after a 20 minute break is a very unusual decoction in that the main decoction now contains 60% of the mash instead of the usual 30%. Because of this size, no shortcuts are taken and a very short protein rest at 50C is taken into consideration. Then the maltose and dextrination occurs until the iodine test is negative, ie it’s fully converted (you may need to adjust the times for the rest at 72C accordingly). Now the decoction undergoes a rather long boil to really extract most of the remaining starches and part of it is returned to the thin mash in the other vessel in order to raise the temperature for a short protein rest at 50C whereas the rest of the mash continues to boil.
Once the entire decoction is returned, the resulting temperature is around 63C and the β-amylase now has a chance to further break down the products made by the α-amylase. This has a noticeable impact on the final attenuation of the beer and will result in much more fermentable sugars than conventional methods.
Give it a go, but beware that the sheer size of the first decoction requires it to be returned very slowly to the main mash in order to avoid unnecessarily scorching the enzymes. Stir a lot, carefully, avoiding to oxygenate the wort (it will make it darker). Bigger breweries pump slowly and have the agitator running in the target vessel at low RPMs. In my case this process takes about 10 minutes. Bigger breweries take about 20-25 minutes to pump back the decoction.