Fushimi at 8am smells like rice and yeast. The breweries start work at 6am, and by 8 the air carries the fermentation smell across the entire canal district. It is not a subtle smell. It is industrial and specific.
The smell comes from the koji rooms — the rice is steamed, mixed with mold spores, and left to ferment in cedar-lined chambers. The cedar is part of the flavor. Newer breweries use stainless steel. The older ones still use wood, and you can tell the difference in the air.
By 10am the smell starts to fade as the morning batch is moved to the next stage. The best time to walk Fushimi is 7:30am to 9:00am. After that you are just walking past buildings.
The fifth-generation brewery on the south canal still opens their windows during fermentation. They say the air quality affects the taste. There is no scientific evidence for this. They do it anyway.