320 FOOD AND FOOD ADULTERANTS. 



PREPARATION OF WINE. 



The growing of grapes for wine and the proper treatment of the j nice 

 for its conversion into wine have formed the subject of numerous trea- 

 tises, that branch of technology having received a great deal of attention 

 and study in countries where it is carried on. Only a short sketch of 

 the leading features of the process can be given here, necessary to a 

 proper understanding of the product itself. 



Wine is properly the pure fermented juice of grapes ; its composition 

 is very variable, and the differences in the varieties of grapes used admit 

 of almost endless modifications of the product obtained from them. 

 Moreover, many other conditions affect more or less the composition of 

 wine, as the nature of the soil, the climate, the method of cultivation 

 pursued, the weather during the particular season when the grapes were 

 ripened, &c. Thus the same variety of grapes when grown under dif- 

 ferent conditions of soil, climate, &c., produces different wines, and 

 even in the same country the same variety of grape produces wines 

 varying considerably in different seasons. 



The most important constituent in the grape is its sugar, from which 

 the alcohol is formed, so as a general rule the grapes are allowed to be- 

 come fully ripened before they are removed from the vine. The first 

 step is the production of the must. To this end the grapes are first 

 bruised and crushed, either by the aid of machinery or by the more 

 primitive but very effective method of trampling them by the feet of 

 men. In some cases, and for very fine wine, the woody sterns are re- 

 moved from the crushed grapes (derapage) . In other cases, especially in 

 white wines, they are left, their contents of tannin making them a de- 

 sirable addition to the grapes. To obtain the juice the grapes are sub- 

 jected to pressure. The amount obtained varies with tbe means 

 employed, the kind of grape, &c., but may be stated at about CO to 70 

 per cent, of the weight of the grapes. For red wines the juice is allowed 

 to stand in contact with the skins a variable length of time until it has 

 acquired from them the desired depth of color, and in this case the fer- 

 mentation commences before the juice is expressed. All musts contain 

 pretty much the same proximate principles, their differences being due 

 solely to the relative proportions of the different constituents. Briefly 

 stated, these constituents are as follows : 



1. Saccharine matter (chiefly dextrose), which may constitute as high 

 as 25 to 30 per cent, of the must. 



2. Albuminoid matter. 



3. Gummy matter, pectin, &c. 



4. Extractive matter, illy-defined substances, comprising the color- 

 ing matters, if any, the flavoring matters, &c. 



5. Organic acids and their salts, comprising malic acid (especially in 

 bad seasons), a slight trace of tamiic acid derived either from the stems 

 or skins, and tartrates of potassium and calcium. 



C. Mineral matters: Phosphoric, sulphuric, hydrochloric, and silicic 

 acids combined with potassium, sodium, iron, and magnesium. 



