"If a white or light colored juice is desired, the crushed grapes are first pressed, the juice which comes from the press being heated to about 165° F., skimmed, run through a pasteurizer at a temperature of between 175° and 200° F. into well-sterilized containers, and then placed in storage.
"If a colored juice is desired, the crushed grapes are heated immediately, usually in aluminum kettles having double bottoms, which prevent the steam from coming in contact with the contents. These kettles usually contain revolving cylinders, the arms of which keep the crushed grapes thoroughly stirred while they are being heated to about 140° F. The simultaneous heating and stirring help to extract the coloring matter from the skins, tear the cells of the berries, increase the quantity of juice obtained per ton of fruit, and give to the must many ingredients of red wine, with the substitution of grape sugar for alcohol of the wine.
"The aluminum kettles are filled and emptied in rotation, thereby making continuous manipulation possible. The presses should be situated below the kettles, so that the hot juice can be drained directly into them. The expressed juice is then reheated to about 165° F., skimmed, and run through the pasteurizer in the same manner in which the white juice is handled. The juice passes from the pasteurizer while still hot (about 160° F.) into the container, which should be sealed immediately. The lower the temperature (above the freezing point) at which these containers are then stored, the less is the danger of fermentation and the more rapidly the juice will clear and deposit its sediment.
"The ordinary receptacles in which the juice is stored are 5-gallon demijohns, 20-gallon carboys, or clean, new barrels or puncheons, well washed and drained. All containers should be thoroughly sterilized before they are filled, and the covers, corks, bungs, cloths, etc., used in sealing them should be scrupulously clean and carefully sterilized. If barrels or puncheons are used as containers, they are placed on skids and firmly wedged to prevent movement. As the juice cools, air laden with fermentation germs is apt to be drawn into the barrels by the decrease in the volume of the liquid. In order to prevent this, tight air-filtering plugs of sterilized cotton are sometimes used instead of the ordinary bungs of solid wood.
"The type of pasteurizer differs in almost every establishment. As the industry is of comparatively recent development commercially, there are few models on the market and each manufacturer has constructed the model best suited to his particular ideas or requirements. There are two general types, however, (1) open, double-bottomed kettles in which the juice is heated to the required temperature and then drawn off, and (2) continuous pasteurizers in which the juice is heated to the required temperature as it passes through the water bath.
"The presses also show great variation in different establishments, either hydraulic, screw or lever power being used, and there is a marked difference between the types of pomace containers. Sometimes the crushed grapes are heaped on burlap cloths the sides of which are folded in, and these burlaps are placed one on top of the other in the press; sometimes press baskets take the place of these burlaps.
"The manufacturers in California and those in the grape-growing regions of the Rocky Mountains seem to have adopted entirely different methods of handling the juice after it is first pasteurized and stored. Most of the eastern juices are red and are obtained from the Labrusca varieties, generally the Concord. When the juice comes from the presses, some manufacturers strain it to remove the coarse particles and then pour it directly into well-sterilized bottles; others siphon it off the sediment in the containers in which it is stored after the first pasteurization and pour it into pasteurized bottles. In either case, the bottles are securely corked and then repasteurized. The California juices, however, both red and white, are made exclusively from Vinifera varieties. They are allowed to settle in the original containers and are siphoned out of these and carefully filtered to make them clear and bright.
"The clearing of the juice is sometimes facilitated by fining or adding a small quantity of a substance which coagulates and when settling carries down with it the solid matters causing cloudiness in the liquid. Such finings may be applied at the time of the first pasteurization or just before the final filtration and bottling. In the latter case the juice is drawn off the settlings in containers, the finings are added, and the juice again pasteurized into other receptacles. When it clears, it is either bottled directly or first passed through a filter, drawn into carefully sterilized bottles, securely corked, and then repasteurized. Care must be taken that the final sterilization is not at a higher temperature than the previous one; otherwise, solid matter may be precipitated and the must clouded again.
"A simple and efficient form of sterilizer consists of a wooden trough provided with a wooden grating which is raised 2 inches from the bottom and on which rest the filled bottles in wire baskets. The trough contains enough water to submerge the bottles and is kept at a temperature of 185° F. by means of a steam coil beneath the grating. It requires about 15 minutes for the must at the bottom of the bottles to reach that temperature; for packages of other sizes it is necessary to make a test with a thermometer in order to determine how long it takes for the entire contents to reach 185°.
"To prevent the corks from being expelled during sterilization, they are either tied down with a strong twine or with some contrivance such as the cork holder. In order that mold germs may not enter the must through the corks, especially if a poor quality of cork is used, the necks of the corked bottles are dipped in heated paraffin before putting on the caps, or the corks are sealed down with sealing wax. It is also well to keep the bottles on their rider to prevent the corks drying out."