WINE, CIDER AND VINEGAR 



181 



Albominoid and nitrogenoas 



matters 



Sugar, gum, etc 



Mineral substances . . . 

 Water 



In 100 parts, 

 grape juice 



1.7 



18.05 



1.7 



75 to 80 



The food value of the grape is greater than that 

 of any other fruit in popular consumption. This 

 superior nutrient quality is due to a larger content 

 of sugar, gluten, mineral salts and fruit acids, 

 together with a lesser quantity of water, than so 

 great a content of nutrients generally affords, 

 especially in the fruits. Grape-sugar (of the grape) 

 is the chief nutritive constituent. The particular 

 advantage which grape-sugar possesess over all 

 other types of sugar is the ease of its assimilation. 

 Grape-sugar, unlike other sugars, is naturally in 

 the state to which all other carbohydrates must 

 be reduced by preliminary digestion before they are 

 ready to be absorbed by the- system. This physical 

 property rests on the fact that its constituent 

 elements are in looser chemical combination, and 

 therefore the greater part of the sugar passes into 

 the circulation unchanged. The grape is unusually 

 rich in albuminoids. It also contains a very fair 

 percentage of vegetable fats. 



Literature. 



Wm. T. Brannt, A Practical Treatise on the 

 Manufacture of Vinegar, etc., Part II (Manufacture 

 of Cider, Fruit Wines, etc.) ; A. Hausner, The Manu- 

 facture of Preserved Foods and Sweetened Meats ; 

 Bioletti and del Piaz, Preservation of Unfermented 

 Grape Juice, Bulletin No. 130, California Experi- 

 ment Station ; Bioletti, A New Method of Making 

 Dry Red Wine, Bulletin No. 177, and The Manufac- 

 ture of Dry Wines in Hot Countries, Bulletin No. 

 167, Calif. Exp. Sta.; Husmann, Home Manufacture 

 and Use of Unfermented Grape Juice, Farmers' 

 Bulletin No. 175, United States Dept. Agric. 



WINE, CIDER AND VINEGAR 



By Samuel C. Prescott 



These beverages are prepared from the sugar- 

 containing juices of fruits by means of the alco- 

 holic fermentation produced by microorganisms 

 known as yeasts. The fermented juice of grapes is 

 known as "wine," while that produced from apples 

 is "cider." Technically, they are very similar. 

 Fermented pear juice is known as pear cider or 

 "perry." The juices of certain fruits or vegetable 

 bodies other than grapes may result in the forma- 

 tion of special kinds of so-called "wines," as "elder- 

 blow wine," "rhubarb wine," and the like. These 

 are produced, however, only on a very small do- 

 mestic scale, and have no importance commercially. 



The alcoholic fermentation. 



The alcoholic fermentation, which is the basic 

 process on which the preparation of cider and 



wine depends, is a chemical change induced in 

 sugar solutions by the activity of a group of 

 microorganisms technically known as the Sacchar- 

 omycetes, and commonly spoken of as "yeasts." 

 Of these there are a large number of species, but 

 the ones of industrial importance, so far as their 

 utilization is concerned, fall, in general, into two 

 more or less distinct types. One of these, the 

 Saecharomyces cerevisice type, includes the yeasts 

 employed technically in brewing, fermentation 

 preceding distillation, as in the manufacture of 

 spirits and of whisky, and in the preparation' of 

 compressed yeasts or other yeasts for bakery or 

 domestic purposes. The second type, the Saechar- 

 omyces ellipsoideus, is used in the fermentation of 

 wine and cider, champagne, and in the fermenta- 

 tion for distillation of brandy. All these organ- 

 isms are widespread in nature, the Saecharomyces 

 ellipsoideus being found especially on the surfaces 

 of ripe fruits and in the soil of orchards and vine- 

 yards. 



The chemical change induced by these organisms 

 consists in the breaking up of sugar into alcohol 

 and carbon dioxid, the latter, a gaseous product, 

 escaping for the most part, unless special effort is 

 made to confine it or absorb it in the fermented 

 liquid itself. Chemically, the change may be 

 expressed by the equation 



CeHioOs = 2C2H5OH + 2CO2 



Grape-sugar Alcohol Carbon dioxid 



This equation, while expressing the change theo- 

 retically, is not absolutely exact, as small quanti- 

 ties of other products, generally called the by- 

 products, are also formed. These include glycerin, 

 succinic acid and traces of other acids and ethers. 



Since the fruit juices in general contain con- 

 siderable amounts of sugar, these are especially 

 susceptible to the alcoholic fermentation, and 

 require only that the organisms resident on the 

 surfaces of the fruits be brought in contact with 

 the juice in order that the change may take place. 

 This is generally accomplished by crushing or 

 grinding the fruits, and in this way the yeasts, 

 together with other organisms which may also be 

 present on the fruits, come into intimate contact 

 with the sugary juice. 



If the desired organisms are predominant, the 

 fermentation is likely to. proceed normally and give 

 a good product. If, on the other hand, organisms 

 of less desirable types gain the ascendency, the 

 fermentation may result in a wine or cider which 

 is bitter, turbid, or in other ways abnormal and 

 unsatisfactory. This may be prevented in a great 

 measure by introducing into the freshly expressed 

 juice a pure culture of a desirable yeast, and 

 thereby artificially making certain that the proper 

 type of organism is in a suitable excess. The fer- 

 mentation may thus be controlled in a way analo- 

 gous to the control of brewing operations by the 

 use of a pure culture of yeast. 



The course of the fermentation is somewhat as 

 follows: After the crushing of the fruit, pressure 

 is applied and a juice, more or less colored, accord- 

 ing to the kind of fruit, is obtained. In wine- 



