When bread making was still a routine part of daily life, one of the housewife's chores would be to tend to the needs of the yeast. In the 18th century and before, there was no difference between brewer's yeast and baker's yeast. In some countries, brewers had the price of the yeast set by the government, so they could not overcharge customer for this household staple.
Along with making bread, many households also made their own beer and cider. Bottle-fermented beer was another regular source of yeast for the house. The yeast sediment that settles to the bottom of the beer bottle, where it could be poured off and fed flour and water to create a baker's starter. Now, before the advent of refrigeration, the yeast starter was subject to spoilage during the heat of summer. Something I found interesting is that older recipes would suggest adding hops to prevent the yeast starter from spoiling. Just like with beer, the alpha acids in hops would prevent pathogens from taking up residence in the yeast starter.
I was curious how well this would work, so I poured off some of my sourdough starer into a mason jar with a few cones of dried cascade hops. I left this on the counter during a 10 day stretch of days in the high 80's to low 90's. As we don't have air conditioning at home, the yeast was 75-83 F. Aside from having to swat away a lot of fruit flies, the jar seemed fine. When it was time to bake, I picked out the largest hop cones, but knew there were some stray leaves floating about in the bread starter.
So, like everything, the good God is in the detail. I'll make this loaf again, but I'd like to try it using some old yellow hops I've been saving for a Flemish red ale.