This observation provided evidence for ending the distinction between ‘artificial’ fermentation in wine and ‘true’ fermentation in yeast products.[1] The previous incorrect distinction had stemmed in part from the fact that yeast had to be added to beer wort in order to provoke desired alcoholic fermentation, while the fermenting catalysts for wine occurred naturally on grapevines; the fermentation of wine had been viewed as 'artificial' since it did not require additional catalyst, but the natural catalyst had been present on the grapevine itself.[8] These observations provided Pasteur with a working hypothesis for future experiments.[3][4]