I can answers in terms of beer brewing. Early on beer would have been spontaneously fermented, that is wild yeast and bacteria native to the environment would ferment the beer. This style of beer still exists, traditionally in the lambics of Brussels which are laid out in a koelschip (big flat pan) so that the local culture would inoculate the wort (unfermented beer) and start fermentation. This style of mixed-culture fermentation is currently undergoing a revival as a reaction to single-culture brews and as a way of capturing terroir in a beverage that is typically made with non-local or imported ingredients (for example, when I brew even an American beer, I use malt from Wisconsin, yeast from California, and hops from Oregon).
So later on (pre-industrial brewing) there is talk of barm, which is the frothy foam on top of a fermenting beer, now known as krausen. This barm could be collected and used to start another beer. Some brewers would also simply use the dregs from the bottom of a fermentor which is known now as the yeast cake. Many brewers also had sticks that unbeknownst to them, still had a culture on it. This stick would be used to stir the wort and thus would inoculate the beer with that yeast strain. This still survives today in Norwegian farmhouse brewing and is called kviek
Before Pasteur but during the industrial period, the quality of beer went up. Before the malt kiln, most beer was slightly smoky and sour. Beers that were fresh were called running ale and beers that were older and stale (meaning sour) were called stock ale. A lot of times these beers were blended to the taste of the drinker. Brewers knew that the barm and the dregs at the bottom of the fermentor were what caused the fermentation. They didn't know it was a single-cell fungus but they were smart and brewers learned that being cleaner and paying attention to details resulted in better-tasting and less-sour beer. Until Pasteur, all beer would be sour if left to age long enough. But with him the old styles of brewing went out of favor and only today are we seeing a revival in traditional brewing.
Good books on the subject:
Good blogs
Actually we have a philologist at my university who wrote about fermentation especially in classical and medieval European literature compared to the rest of the world.
See, most cultures spit in their brew. Why? Because of the enzymes in spit starts the fermentation process, and with added yeast to fully complete the brew. His thesis was that there was a spitting culture in Europe, although there are no direct reference to it happening.
He used the nordic texts to deduce that Odin's spit in a vat of grain helped a woman win a brewing challenge(very paraphrased here, but you get the jist). By that, and other contemporary sources, he concluded that there might have been a spitting culture in at least Northern Europe. As for the yeast, we have sources in Norway dating back to the high middle-age (correct me on this, can't remember exact century) where yeast was added on purpose.
And if you think spitting is something odd, it really isn't. If you look at native American cultures, especially in middle to southern America, you can find lots and lots of tribes using the spitting method to make beer or an equivalent of beer. This is a social event where motsly women gather around and gossip. This is commonly found in Asia, the Middle-East, Africa and the Americas.
Edit: when I say beer, I just use my understanding of the colloqiual term for alcoholic drink. Ale is a specific type of "beer", as you can't call the proto-ales for true ales.