MANUFACTURE OF WINE 341 



Beer defects may be caused by any of a number of factors. Haze 

 may be due to unstable protein, tannin-protein complexes, resins, or 

 undesirable organisms such as wild yeasts or Sarcinae. 



The Manufacture of Wine. Wine by official definition is the prod- 

 uct of alcoholic fermentation of the juice of sound, ripe grapes. 

 However, alcoholic beverages produced from other fruits, such as 

 berries and citrus fruits, have also been called "wines." 



Wines can be differentiated into the red or white wines. The 

 former are those containing the coloring matter from the skin of 

 red grapes and the latter are those made from white grapes or the 

 juices of other grapes. Wines are also differentiated into the dry or 

 sweet wines. The former are those in which fermentation has been 

 allowed to go to completion so the sugar has been largely depleted; 

 the latter are those in which fermentation has been stopped so there 

 is considerable, relatively speaking, residual sugar. Space does not 

 permit a detailed discussion of the classifications or manufacture 

 of the various types of wines (grape). Only a brief outline will be 

 given here of the general procedures followed in the manufacture 

 of wine. 



A fine wine is obtained only when grapes of good quality are used 

 and sound manufacturing practices are followed. The characteristic 

 bouquet and aroma of a given wine are often dependent on the grapes 

 of a certain locality. Grapes may vary in their quality from year 

 to year, even in the same locality ; hence the interest of the connois- 

 seur of wines in the year of the vintage. Accordingly, old wines are 

 not necessarily better than more recent wines. 



Selected grapes are crushed without stemming (Cruess advises leav- 

 ing stems on the grapes) and then treated with potassium metabi- 

 sulphite, sodium bisulphite, or sulphur dioxide. In the old days, 

 sulphur was burned in the vats to furnish the sulphur dioxide. This 

 pre-fermentation treatment of the grapes destroys or inhibits unde- 

 sirable wild yeasts, bacteria, and molds but allows the wine yeast 

 to develop. 



Several hours after this treatment, the starter is added, selected 

 strains of Saccharomyces cerevisiae var. ellipsoideus being used. The 

 starter, which is about 2 to 5 per cent of the volume of crushed grapes 

 to be inoculated, is prepared. "Must" (unfermented juice) which 

 has been sterilized is often used as the culture medium of the original 

 culture. Successively larger volumes are inoculated until the starter 

 is prepared. 



Generally, the crushed grapes furnish adequate nutrients for the 

 development of yeast. According to Joslyn and Cruess ^^ the opti- 



