How to best deactivate yeast?

How to best deactivate yeast?

I’ve been using an overfermented sponge for dead yeast. While making some French like loaves, I noted a flavor I did not care for. I tried the same technique, but instead of using flour, using malt extract in water and brewed much like beer, using instant yeast instead of a strain of brewers yeast. This has been interesting, with some mixed results so far, one batch of which had a lot of dead yeast, and it worked very well. However, like homebrewing, it involved a lot of sanitation steps, boiling of the wort, etc, and was from a labor standpoint, more work than the less good tasting flour-based overfermented sponge.

All I’m interested in is dead yeast to help relax dough. So far as I know, dead yeast is known as “deactivated yeast” in baker’s terms.  This is a product that is available to pizza shops, but so far as I know, is not available to consumers at retail level. A search this morning led to an SFBI pdf  which suggests nutritional yeast.  Does nutritional yeast flavor the baked bread in the same way as pizza shops “deactivated yeast”?  

Alternatively, is there some fast and easy way to deactivate baker’s yeast?

An idea that occurred to me just this morning would be to use any form of dry baker’s yeast, I’d use instant yeast.  Dissolve it first in 4 times its weight of water for 10 minutes or so, then microwave it, or mix it with additional boiling water, the objective being to bring it above the temperature that would kill the yeast to break its cell walls.  Has anyone tried this?

This could also be practiced on a batch of malt extract grown bread yeast to insure the yeast that was killed was the freshest available.

Source: Fresh Loaf