It was not recognized that many of the diseases of fermented liquids are occasioned by foreign yeasts; moreover, this process, as was shown later by Hansen, favours the development of foreign yeasts at the expense of the good yeast.
In the United Kingdom the employment of brewery yeasts selected from a single cell has not come into general use; it may probably be accounted for in a great measure by conservatism and the wrong application of Hansen's theories.
Pure Cultivation of Yeasts.-The methods which were first adopted by Hansen for obtaining pure cultures of yeast were similar in principle to one devised by J.
By this method several races of Saccharomycetes and brewery yeasts were isolated and described.
Cerevisiae, is never found wild, but the wine yeasts occur abundantly in the soil of vineyards, and so are always present on the fruit, ready to ferment the expressed juice.
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