The Gründliche und Nütze Beschreibung is a lengthy text and I will probably not be able to post a section of it anywhere near daily, but in the process of looking through it I leafed through the Oeconomia again and found this reference to beer yeast:
Of the foam or yeast (Schaum, Hefen oder Gest) of the beer and of brandy
(marginalia: Beer, how it is known to be good by its foam (Gescht))
A little must also be said of these things here, that many are accustomed to judge beers by their foam. If a beer keeps its foam long, it is taken for a good beer. But beers have two kinds of foam (Gescht oder Schaum).
(marginalia: Beer has two kinds of foam (Gescht oder Schaum))
One derives from an internal cause when the beer is first brewed and foams and ferments strongly, and this is, as it were, the flower of the beer. It is thin, uneven, solid, and floats on the top of the beer, and when the beer has finished fermenting, it becomes thick and gradually sinks to the bottom.
The other kind derives from an external cause, that is from shaking or pouring, and it goes away and eventually disappears. Barley beers have copious, but thin foam, wheaten ones have less, thicker, whitish, and it barely covers the surface of the beer in the pitcher.
The yeast or barm (Hefen oder Bermen) are a thick, earthy and heavy matter that sinks down in the beer and settles at the bottom of the cask, and it is warm and dry by nature, and bloating, as we see from the beers that cause belching (auffstossend machen) and the doughs that it causes to rise and blows up (gehend machen und auffblasen).
From these, a good husbandman customarily makes a good brandy or aqua vitae (Brandtenwein oder Aquam vitae) for his household so he needs not seek out or buy it elsewhere.
(marginalia: Yeast, what use it is)
The yeast that is left over after this when the brandy has been drawn off are good to maintain his livestock and especially the pigs that thrive on it mightily well, grow and fatten, which is why some people derive their income and maintenance specifically from brandy and pigs.
This is an interesting text for several reasons: Firstly, because it states clearly that beer yeast was used as a leavening in the context of private households. Second, because it gives us an idea of what beers were expected to look like. Such visual cues are uncommon, and they can help us understand what to aim for in reconstructing foodstuffs. Third, it gives us an insight into the frugal resource management expected of even wealthy households. Beer would be brewed in the home, the barm distilled to produce liquor, and the residue fed to pigs. Very little would go to waste here.
Johann Coler’s Oeconomia ruralis et domestica was a popular book on the topic of managing a wealthy household. It is based largely on previous writings by Coler and first appeared between 1596 and 1601. Repeatedly reprinted for decades, it became one of the most influential early works of Hausväterliteratur. I am working from a 1645 edition.