The making of fruit juices is an outgrowth of the preserving industry. Preserving, as commonly known, is a process of saturating a fruit pulp during cooking, or a partial drying process, so thoroughly with common (cane) sugar that by the action of the sugar alone decay is prevented and the fruit held in palatable condition for months, even years. The art of canning is based on another principle, that of destroying by excessive heat the ferment-producing organisms, in which process sugar is often used to secure a palatable product, its preser vative effects being a secondary con sideration. The fruit juices sold for soda-fountain and flavoring purposes are thickened and preserved, in large measure, by the liberal use of cane-sugar, and are more in the nature of syrups than of fruit juices.
As might be inferred from the above, the first attempts to manufacture fruit juice products util ized a considerable quantity of sugar ; so, today, many manufacturers are using sugar in larger or smaller quantities, and the home maker of grape juice usually finds it convenient and an insurance against "spoiling," which is but fermentation, also to use sugar in considerable quantity. Sugar does not destroy the basic flavor of the juice, and with some varieties of grapes, or even with the best grapes in cold wet seasons, when the sugar content of the juice is low, its use is essential to produce a palatable product ; but with perfect sterilization this is entirely unnecessary, and its use has an effect on the medicinal value of the juice, and covers up and obliterates the more delicate flavors and aroma which are preserved by the more scien tific and careful methods of manufacture without sugar.
The manufacture of grape juice, and also both apple juice and orange juice, as sold for beverages, is based on the principle of sterilization and per fect cleanliness, not preservation by sugar or other wise. Grape juice, as marketed today, is an undi luted, unadulterated and unpreserved product. It is the pure juice of the grape, sterilized as it comes from the fruit, put up in sterile bottles, handled only in sterilized machinery, and sold to the consumer, still contained in sealed and sterilized smaller bottles. The ordinary housewife can dupli cate this process in her own kitchen with very little trouble by the observance of the one rule, namely, perfect sterilization of everything that comes in contact with the juice, and the applica tion of such a degree of heat to the fruit and the juice as will keep it perfectly sterilized at all stages of the process. The commer cial product is allowed to stand in its first containing vessels, after being drawn from the presses, for at least three months to settle, and is then drawn away from the sediment, which formerly was thrown away but is now a valuable by-product. In the kitchen this settling must be provided for, if best results are to be secured. A second sterilization is necessary when the juice is changed from the settling vessel to the smaller bottles.
Details of the processes.
Fruit juices, other than grape and apple juice, are made by cooking fresh fruit, pressing it and adding sugar to the juice, and cooking or evaporating it down to a consistency of thick cream, in which con dition preservation is not difficult. This product is used for flavoring in the manu facture of confectionary and baked goods, and as the flavoring part of the commonly sold soda-fountain beverages. Apple juice is made by pressing apples as for cider but using a better grade of apples, and following by an immediate sterilization and bottling of the prod uct. The sterilization prevents fermentation and the product is a pure apple juice. Orange juice is put up in the same way.
The manufacture of grape juice begins with the picking of fully ripe grapes, of good quality. In vineyards that are free from rot, " run of vine yard " grapes are used, but they are allowed to remain on the vines and mature some weeks after picking for commercial purposes has begun in other vineyards. The grapes are taken to the fac tories in picking crates, holding forty to sixty pounds each, and taken by an elevator to an upper story and passed through a stemmer. The stems contain a large proportion of tannin, and if kept with the grapes will affect the flavor of the juice. After being stemmed, the grapes are placed in aluminum steam-heated kettles (Fig. 263), large enough to hold fifteen hundred to two thousand pounds each, and gently heated, not boiled. Care is taken at this point, as in every application of heat to the grape and its products, not to allow too high temperature. If the temperature at any time reaches the boiling point, a "burned taste" is caused. The color comes from the pigment cells of the skin, and can be varied by the amount of heat and pressure used. At the first heating, not more than 100° Fahr. is used. The seeds do not lose their vitality in this heating process. The minimum heat used in most factories in this stage is 80' Fahr., although what is known as the "light juice' is made in some factories by pressing before any heat is applied, thus leaving the pigment cells in the skin undisturbed. The heated mass of juice, pulp, seeds and skins is then placed in power presses, usually hydraulic, where it is subjected to great pressure. (Figs. 263, 264.) The juice again goes to the heating kettles, where it is heated to at least 180° Fahr., this being the lowest point of sterilization. Heating above this point spoils flavor, and it is the aim of the manufacturer to maintain a steady temperature at this point until the stor age in the five-gallon carboys is completed and the juice sealed in these receptacles. (Figs. 265, 266.) Here it stands three months before being put into the smaller bottles for the wholesale and retail trade.