THE MICROBIOLOGY OF ALCOHOL PRODUCTS 523 



The materials used are soluble gelatinous or albuminous substances which are 

 capable of being coagulated and precipitated by some ingredient of the wine. The 

 best of the commonly used substances are isinglass (ichthyocol) 2 or 3 g. per hecto- 

 liter, for white wines; the white of fresh eggs, i or 2 per hectoliter for red; and 

 gelatin, 10 or 12 g. per hectoliter for either. 



The proper quantity of the finings is dissolved in a little water diluted with wine 

 and stirred into the cask. The tannins and acids of the wine cause a gradual coagula- 

 tion in minute particles throughout the liquid. These particles gradually coalesce, 

 forming larger particles which include aU the other floating solid matter of the wine 

 as in a net. These larger particles contracted by the alcohol then settle to the 

 bottom, leaving the wine perfectly bright. 



The coagulum consists of a combination of the gelatinous matter and the tannin. 

 Some of the latter, therefore, is removed from the wine. With astringent red wines, 

 this may be an improvement. If there is no excess of tannin present, enough must 

 be added to combine with the finings used. With white wines which contain little 

 or no tannin, this addition is always necessary. 



The amount to use varies with the quality of the finings and of the tannin and 

 with the composition and temperature of the wine. 



To precipitate commercial gelatin of good quality about an equal quantity of 

 good tannin is necessary; isinglass properly prepared requires only from one-half to 

 one-third this amount. Eggs require only minute quantities. 



Specially prepared casein pf milk is used for fining white wine. Its chief merit is 

 that the acids of the wine alone cause its complete precipitation and no addition of 

 tannin is needed, though a little is sometimes helpful. Many other albuminous 

 substances such as milk, blood and various proprietary preparations are also used, 

 but they are all inferior to the three mentioned and many of them introduce foreign 

 matters such as milk sugar and bacteria which are a source of danger to the wine. 



Wines containing many disease-producing bacteria may be injured by the intro- 

 duction of finings. The evolution of gases due to the bacterial action may prevent 

 the settling and the protein matters introduced will favor the multiplication of the 

 disease-producing organisms. By the use of s to 10 g. of sulphurous acid per 

 hectoliter added to the wine immediately before the addition of the gelatin, the 

 bacteria may be temporarily paralyzed and the finings will then settle and remove 

 the bacteria with the other floating particles. 



The bright wine should be racked from the finings very soon after the sediment 

 has settled, especially when disease-producing bacteria are numerous. This will 

 be in from ten to twenty days. If the wine is not clear in three weeks it should be 

 filtered. 



Filtering is inferior to fining in producing a perfectly bright wine. It is more 

 rapid, however, and is useful in clearing common wine and wines refractory to fining. 



Filters of innumerable forms are used. They are of two main types. For rough 

 clearing of very cloudy wines some form of bag filter is usually employed in which the 

 wine passes through a cloth tissue. The passage at first is rapid and the filtration 

 imperfect. As the solid matter accumulates on the filtering surface, the filtration im- 

 proves but the passage of the wine is retarded. The first wine is passed a second time 



