CONDENSED or EVAPORATED MILK. The invention of the process of ing milk is generally attributed to Gail Borden in 1856, but some authorities assert that it was invented in Switzerland. In view of the enormous present dimensions of the industry, it is interesting to note that the Patent Office Examiners were with diffi culty induced to grant a patent because they insisted that milk could not be evapo rated in a vacuum.
It was the exigencies of the Civil War which first secured national recognition for condensed milk and advertised its merits throughout the world. It soon after be came a commodity of universal use on ocean steamers and in mines, forests and con struction camps, reaching ultimately every nook and corner of the universe.
There are to-day more than two hundred factories in the United States, all using the vacuum process. The industry consumes yearly more than 600,000,000 pounds of fluid milk and the product totals to between five and six million cases of forty-eight cans each.
The fundamental requirement of all first-class condensed milk is absolutely pure milk produced under the most hygienic conditions. As typical of the pains taken to ensure this, one may take the contract between a first-class factory and the farmer. It is full of all manner of stringent conditions. The factory binds itself to take an average of so many pounds of milk per day for each month of the year, at so much per hundred pounds—the price being higher during the winter than during the other months. The farmer, on his part, agrees that his cows shall be fed upon particular food, that they shall not eat turnips, brewery or distillery grain, or any other food that will impart a disagreeable flavor to the milk or reduce its richness ; to hold the milk room at a cer tain temperature, and with a certain amount of ventilation ; that the cows shall be kept clean and groomed ; that the cans shall be washed and placed in the sun when they are not in use, and that they shall be turned down, bottom upwards, on a rack at least three feet from the ground ; that he will report any sickness in his animals, employes or fam ily, etc. In short, every possible precaution, including traveling inspectors, to see that all requirements are fulfilled, is taken to secure proper care and cleanliness. It is in these respects that milk used for making condensed milk is generally superior to the ordinary store milk.
To fully appreciate the principle employed in the manufacture of condensed milk, one must remember that the composition of milk includes from 84% to 90% water (see article on MILK). Any desired part of this water can be extracted without taking anything from its food value, for the latter is found in the fats, milk-sugar, casein, etc., all of which remain in the condensed or evaporated product.
In the manufacture of Sweetened Condensed Milk, the liquid milk is strained, cleansed in centrifugal separators, heated to the proper temperature to expel the gases of the milk and destroy the germs, again strained, mixed with a certain quantity of standard granulated sugar and run into vacuum pans where it is "condensed" by evaporation— boiling in a vacuum at a very low temperature—of part of its water contents. It is then ready for canning.
The vacuum pan employed is an egg-shaped copper vessel heated by interior steam coils and an outside steam-jacket around the lower portion. In one side of the dome is a small window, through which a light illuminates the interior, and opposite is an eye glass through which the condition of the contents may be observed. The pan is also pro vided with a vacuum gauge, test sticks, etc.
Good sweetened condensed milk will keep for years, but all kinds will gradually thicken in time—poor brands naturally becoming thick and hard far sooner than well made full-cream products. The cases should not be stored near boilers, steam pipes or any extreme heat. At home, as a can seldom outlasts the day, it is not likely to spoil, but the best place for it is in the refrigerator, so covered as to prevent it from absorb ing the flavors of meats, etc.
The Unsweetened Condensed Milk, largely used for city consumption and delivered in bottles, is made by the same method as the Sweetened except that the sugar is omitted. It is not intended for long keeping.
Evaporated Milk is the trade designation for milk, without sugar addition, evapo rated in vacuum pans to the consistence of cream, then run over cooling pipes and into cans and immediately sealed, followed by the same "cooking" for sterilization pur poses as any other canned goods. The result is an unsweetened product which will keep good almost indefinitely. After coming from the sterilizer, the cans are agitated in a shaking machine which breaks up the fat globules and are then stored in warm rooms until "cured" to the right degree.
Though the same principle is employed in all condensed and evaporated milks, there is plenty of room for discrimination in purchasing different varieties. The best grades should be creamy-white, smooth, free from a "cooked" taste, of just the right consistence, etc. Furthermore, there is a wide range in food values, for the latter naturally depend on the amount of water extracted.
Evaporated milk of good quality is, when diluted with two-thirds of its bulk of pure fresh water, almost if not quite the equal of fresh milk.
U. S. "Standard" Condensed or Evaporated Milk must contain not less than 7% of milk fat and not less than 28% of milk solids, including milk fat.