This went straight from medieval guilds to the 1920s, but actual bread mass production started in the Victorian era, and people did have a big negative reaction to that. They adulterated bread in ways that poisoned consumers during that period, which was a tad unpopular.
That drove consumers to some curious brands: https://en.wikipedia.org/wiki/Aerated_Bread_Company
> They adulterated bread in ways that poisoned consumers during that period, which was a tad unpopular.
Consumers paying attention to how products impact them. No kiddin’.
Specifically, copper sulfate was added to flour to slow the rate of fermentation. Highly toxic.