German Brewing

Do you use a decoction to mash out?

I used to think yes, but with reading the claims about new starches being released during the decoction, I wonder if it is really a good idea. Do you want new starches at the point you kill all the enzymes? Are they instantly converted at those temps and its really no big deal?

What has been your experience?

It's always a thin decoction to mash out. That said, I prefer to direct heat to mash out but YMMV

Mashout doesn't kill the alpha amylase, that's American homebrewing dogma. 75-78c is the normal mashout temperature, and also the temperature maintained during the sparge to allow the alpha to convert any leftover starch that is rinsed free through sparging. I don't think alpha denatures until 80+.

Iodine tests are pretty much mandatory with decoctions.

The extra starches are the desired effect and yield a much higher efficiency. Even a tick mash to the 77 step converts (quite fast actually). The iodine test will show you.

For the squeamish sceptics a "Malzauszug" is recommended. Basically you save a portion of the mash before the first decoction was pulled. It's very enzyme rich. If you cannot get the last stage to convert then this is added.

For the usual Hochkurz, double or triple decoctions I found it never necessary. They always converted (measure it to be safe).

On a triple decoction the last portion may just as well be lauter or normal because at this stage it's unlikely to extract another significant amount of starches. One doesn't need to let it settle first and it's easier to pump.

Iodine solution at 0.02N is generally used. It's widely available via eBay for eg