Besides the milk and cream, several other manufactured milk products are used in ice-cream. What has been said previously about the milk and cream applies also to the milk for these products. The quality, especially the flavor, is very important.
There is a difference between condensed and evaporated milk, but because of their similarity, both in composition and manufacture, they will be considered together. Condensed milk usually has sugar added to preserve it, although some ice-cream-makers use it without added sugar, when it is known as plain in contrast to sweetened condensed milk. The evaporated milk is usually sterilized in sealed cans to preserve it, no sugar being added. More condensed milk is employed in making ice-cream than evaporated milk. The condensed is usually shipped to the ice-cream manufacturer in bulk, either in milk-cans or barrels.
—The water is removed from the milk by heating under reduced pressure. The heating is usually done in a copper pan. (Fig. 5.) This is accomplished by means of a steam jacket on the bottom and usually one or two steam coils in the pan. Before drawing the milk into the pan, it is heated in an open copper vessel, by turning direct steam into the milk. This container is called the hot well or fore warmer. The temperature varies according to whether plain or sweetened condensed is being made. The sweetened is heated higher to dissolve the sugar. The object of heating under reduced pressure is to reduce the boiling point. At ordinary pressure milk would boil at the same temperature or a little above that of water. At this temperature the milk could not be condensed without imparting a pronounced cooked flavor and caramelizing a part of the sugar.
Fig. 5.—View of modern condensory showing hot wells, vacuum pan, vacuum pump and cooling tanks.
The vacuum in the pan is produced by means of a vacuum pump. A vacuum equal to a column of mercury about 25 inches is usually maintained. The condenser is located at the top of the pan and is directly connected with it. As the milk boils, the vapor passes from the pan into the condenser. In the latter the vapor comes in contact with a spray of cold water which causes it to condense. The pump carries off the condensing water and the condensed vapor. When the desired density is reached, the milk is drawn from the pan and cooled. The proper concentration of the milk is determined by a special graduated scale known as the Baumé. A more recent method is an electric resistance. If sweetened condensed is being made, the sugar is added to the milk, the mixture of sugar and milk are heated to dissolve the sugar before drawing them into the pan.
Sometimes the milk is superheated; this consists of turning live steam into the milk just at the time that the desired concentration is reached. It gives the condensed milk more of a “livery” appearance, which is probably due to the precipitation of the albumen.
The length of time required for condensing the milk to the desired consistency varies with the amount of milk in the pan, amount of heating surface, size and capacity of vacuum pump, and amount and temperature of water in the condenser.
—The following standards are given by the United States Department of Agriculture:[9]
[9] Office of the Secretary, U. S. Dept. Agr., Food Inspection, Decision 170, 1917.
“Sweetened condensed milk, sweetened evaporated milk, sweetened concentrated milk, is the product resulting from the evaporation of a considerable portion of the water from the whole, fresh, clean, lacteal secretion obtained by the complete milking of one or more healthy cows, properly fed and kept, excluding that obtained within fifteen days before and ten days after calving, to which sugar (sucrose) has been added. It contains, all tolerances being allowed for, not less than twenty-eight per cent (28.0 per cent) of total milk solids, and not less than eight per cent (8.0 per cent) of milk fat.
“Condensed skimmed milk, evaporated skimmed milk, concentrated skimmed milk, is the product resulting from the evaporation of a considerable portion of the water from skimmed milk, and contains, all tolerances being allowed for, not less than twenty per cent (20.0 per cent) of milk solids.
“Sweetened condensed skimmed milk, sweetened evaporated skimmed milk, sweetened concentrated skimmed milk, is the product resulting from the evaporation of a considerable portion of the water from skimmed milk to which sugar (sucrose) has been added. It contains, all tolerances being allowed for, not less than twenty-eight per cent (28.0 per cent) of milk solids.”
Condensed or evaporated milk should be purchased only on its composition, both fat and solids not fat. For method of testing, see Chapter XIV.
—“First. The plant should be located in a community which is not only thoroughly adapted in every way to a high standard of extensive dairy farming, but is already far advanced in such development. The herds of cows should be large, healthy, well cared for, and of a breed or breeds that produce a grade of milk reasonably adapted for condensing purposes and the production of a standard product.
[10] These conditions are taken from the U. S. Dept. Agr., Weekly News Letter, Vol. II, No. 45.
“Second. In establishing a plant for condensing milk by the vacuum process it is of primary importance that the location provide an abundant, steady supply of pure, cold water, independent of the supply required for boiler use. The quantity of water required to condense a given quantity of milk will, of course, vary with the operating conditions, such, for example, as the temperature of the condensing water and the temperature (or the pressure) of the vapor to be condensed. A general idea of the importance of water supply can be obtained from the authoritative estimate that about 3 gallons of water are required for the condensing of one pound of fresh milk (about one pint). Difficulty in obtaining an adequate supply of good, pure, cold water is a cause of serious embarrassment to some of the commercial condensories now established, and the lack of it has been the cause of many failures.
“Third. An abundant supply of milk is an absolute necessity. The exact quantity required daily will, of course, vary with the size of the plant. Several reliable authorities have estimated that for the profitable production of condensed milk on a commercial scale the supply of raw milk to the factory should not fall below 15,000 pounds a day. This estimate is exclusive of the daily supply of milk normally required for other purposes by the community. Furthermore, if the finished product is to be of marketable quality, the milk received at the condensory must be of exceptionally high grade; that is, clean and pure. While first-class milk is essential for the manufacture of a first-class dairy product of any kind, it is absolutely necessary if a condensed milk factory is to be a success. If a few cans of low-grade milk are not detected at the receiving platform of a condensory, the slight defects in the raw milk are multiplied in the process of condensing it, and the result is practically certain to be the complete loss of the whole batch, which may represent a financial loss of several hundred dollars. This statement may be illustrated concretely: It is claimed by authorities that raw milk containing as much as 0.2 per cent acid (calculated as lactic acid) is not fit for condensing purposes. This does not necessarily mean that it would taste sour, but if accepted and condensed in the ratio of 2.25 to 1 (it may be more but is seldom less), the acidity, increasing in the same ratio, would reach 0.45 per cent, which would be practically certain to cause a sour taste in the finished product. Every housewife knows that sour milk will coagulate or curdle on heating, and that the higher the temperature the more rapid is the curdling process and the finer the curd. This makes it unfit for cooking purposes. In the commercial production of evaporated milk, the product must be sterilized in the cans at a very high temperature in order to insure a good keeping quality. It is obvious, therefore, that if milk is delivered to the factory with a slight excess of acidity, it would probably be impossible to sterilize the product obtained from it without producing a hard curd, which would make the product absolutely unsalable, and thus a total loss to the manufacturer. Furthermore, excessive acidity, which is principally caused by improper care and handling of the milk, is not the only condition that may render milk unfit for condensing. Other undesirable qualities of the milk may also be induced by poor health and improper care of the cows, by the kind and the condition of their feed, and by many other details of imperfect management of the dairy farms.
“The services of experts thoroughly qualified by training and long experience in this particular line will be required to detect and guard against these unfavorable conditions.
“Fourth. Adequate facilities for marketing constitute another essential to the commercial success of a condensed milk plant. Commercial success, of course, implies a profitable market for the product—a market which is readily and directly accessible to the plant without adding excessively to the cost of manufacture, either in the form of high freight rates or long hauls from the condensory to a railroad. As already indicated, the successful manufacture of condensed milk on a commercial scale requires a large output of the finished product—a very much larger output than is likely to be consumed in the local market; therefore, in selecting a location, favorable transportation facilities to a good market or markets are a consideration of vital importance to ultimate success.
“Fifth. In establishing and operating a condensory, the necessity of adequate capital is another important question. The cost of buildings and equipment will, of course, vary with the purchase of superior or inferior materials and workmanship, as well as size of the plant, and, in some measure, the kind of condensed milk to be produced. In any case, however, the buildings should be thoroughly substantial, more so than is commonly considered necessary for a creamery or a cheese factory. The major part of the equipment is a very highly specialized, more or less complicated, and very expensive type. The proper operation of the equipment, especially the vacuum pan, and the sterilizer when the product is sterilized in cans, calls for a high degree of skill and large experience, if serious losses are to be avoided and a standardized legal product is to be produced. The cost of buildings, equipment, and operation of a plant for the manufacture of evaporated milk (unsweetened condensed milk for household use) will illustrate the capital required for the manufacture of any other form of condensed milk. Some reliable authorities have conservatively estimated that adequate buildings and equipment for a minimum production on a commercial scale would cost in the neighborhood of $25,000, exclusive of working capital. The markets for condensed milk at best are very unstable. Frequently, the manufactured product must be held several months before it is marketed. In the meantime, the plant must be kept in operation, for which a very considerable surplus capital must be provided. The same authorities estimate this item at $10,000. It therefore appears that in establishing and operating a milk condensory, capital to the amount of at least $35,000 must be provided. That this estimate is conservative is indicated by the fact that manufacturers of condensed milk have stated that a capital of $50,000 is usually necessary to operate a condensed milk factory.
“Sixth. Commercial success in any manufacturing enterprise usually requires much more than merely placing the product upon the market. A demand for the product must be firmly established and a regular trade developed before success is assured. To attain such a result the new product must meet the keen competition of similar products already well established. There are many well-established brands of condensed milk now on the market. There may be room for many more, but new brands, regardless of their quality, must expect to overcome strong competition before a firm foothold is gained. This usually requires extensive advertising and a competent, vigorous sales force, which entails a heavy expense. Good salesmanship and advertising must be continued. The necessity of a thoroughly organized selling organization should, therefore, not be overlooked.”
—From the above conditions essential for a condensory, it is evident that an ice-cream plant would not be justified in trying to operate one, unless also they maintained a large milk and cream receiving plant in the country. It is the usual practice for the ice-cream manufacturer to purchase the supply of condensed milk. However, some plants have a condensory in connection with their country plant, which is operated successfully. When the supply of condensed milk is purchased, the basis of payment should be the composition. For the methods of testing condensed milk, see Chapter XIV.
In certain localities, especially the South where it is hard to secure milk and cream, milk powder and butter are often emulsified or homogenized to make cream. Milk powder is also employed in the same way to meet sudden demands for cream. Milk powder is often used in ice-cream to increase the milk solids not fat and thereby give a firmer body and a smoother texture. The composition varies in fat from skim to whole milk.
—The following standards are given by the United States Department of Agriculture:[11]
[11] Office of the Secretary, U. S. Dept. Agr., Food Inspection Decision 170, 1917.
“Dried milk is the product resulting from the removal of water from milk, and contains, all tolerances being allowed for, not less than twenty-six per cent (26.0 per cent) of milk fat, and not more than five per cent (5.0 per cent) of moisture.
“Dried skimmed milk is the product resulting from the removal of water from skimmed milk and contains, all tolerances being allowed for, not more than five per cent (5.0 per cent) of moisture.”
—Two patented processes of making powdered milk are in general use in this country at the present time, the Merrell-Soule and the Ekenberg.
[12]—“The desired process must, it was evident, be one which would not affect the active principles or the nutritive qualities of milk, nor change its chemical reactions in any way. The product when reaching the consumer must be, in every essential quality, fresh milk.
[12] This article is taken from the publication, “Merrell-Soule Powdered Milk for the Dairy, Creamery and Ice Cream Plant,” Merrell-Soule Co., Syracuse, N. Y., 1918.
“The methods known as condensation and evaporation, also the earlier milk powder processes, were efforts to achieve the desired result. But in none of them was the goal completely attained, as it is to-day in Merrell-Soule Powdered Milk—the product of a perfected process.
“Liquid Milk is seven-eighths water. Merrell-Soule Powdered Milk contains approximately 2 per cent of moisture. Transportation cost is thus reduced to a very small percentage of the expense of shipping liquid milk. The fact that powdered milk may be shipped by freight, while liquid milk must go by express or baggage, means an additional saving.
“The expense of shipping powdered milk is also, of course, much lower than the transportation cost of the condensed product.
“The Merrell-Soule process reduces the bacteria count to a remarkably low figure, and it is a demonstrated fact that the bacteria which are to be found in the fresh-made powder tend to die off, rather than propagate, during storage.
“Merrell-Soule Powdered Milk is quickly and easily dissolved in water, and the ‘reconstituted’ liquid milk thus obtained is pure, fresh milk, with the delicate odor and unmistakable flavor of fresh milk, and with every chemical reaction and nutritive property of fresh milk retained unchanged.”
—“The history of powdered milk dates back to the middle of the last century, when an inventor named Grimwade patented, in England, the first commercially usable process.
“He added carbonate of soda to fresh milk, evaporated it in open-jacketed pans, with constant agitation, until a dough-like substance resulted; added cane sugar, pressed the mixture between rollers into ribbons, dried it still further, then pulverized it.
“This process, cumbersome and unsatisfactory as it must have been, was in practice for some years. Other processes followed at intervals for half a century, but the real commercial development of the industry dates back only about twenty years.
“It was in 1899 that a machine for the drying of milk by what has since become known as the ‘double roll’ process was invented by W. B. Gere, since deceased, then secretary of the Merrell-Soule Co., and I. S. Merrell, first vice president of the company. But the ‘dry milk’ which resulted from this process was not satisfactory, and for that reason was not put on the market by the Merrell-Soule Company.
“Several other processes were then tried out, but none proved satisfactory until Lewis C. Merrell, brother of I. S. Merrell, hit upon the spraying of milk into a regulated current of heated air. This gave the quality that had been desired, and the next thing was to determine the commercial value of the process.
“In January, 1905, a building owned by the Merrell-Soule Company at Fayetteville, N. Y., was equipped, and powdered milk was produced, in a small way, by this spray process. Enough was marketed, and with sufficiently gratifying results, to warrant the company in going ahead with the enterprise.
“Meantime, patents had been applied for, and the patent office had referred the Merrell-Soule Company to a United States patent granted in 1901 to Robert Stauf, of Posen, Germany, which seemed to cover the process. F. C. Soule, president of the Merrell-Soule Company, thereupon went to Germany and bought not only the United States patent held by Stauf, but also thirteen foreign patents owned by Stauf and his associates.
“The wisdom of the purchase of all the patents held by the Stauf interests has since been amply demonstrated. In 1915, patent litigation which had been in the courts for three years was decided by the Court of Appeals in favor of the Merrell-Soule Company, the decision being based on this company’s possession not only of its own patents, but also of the basic patents governing the spray process of powdered milk manufacture.
“Following the success of the experiment at Fayetteville, the construction of the first Merrell-Soule Powdered Milk factory, at Arcade, N. Y., was begun in 1906. Before this factory was completed, it had been discovered that a better product could be obtained by condensing the milk in a vacuum pan before spraying. This resulted in new patents covering what was known as the Merrell-Gere process, embodying the original Stauf method and the improvement mentioned.
“Since then many other improvements have been made at the Merrell-Soule plants, many other patents taken out. The first powdered milk factory, at Arcade, was followed by a second, at Little Valley, N. Y., in 1909. Since then factories have been established at Frewsburg, N. Y., Union City, Pa., Waterford, Pa., Farmersville Station, N. Y., Warsaw, N. Y., Gainesville, N. Y., Attica, N. Y., and Omaha, Neb.
“Consumption of milk has increased from 18,000 quarts per day, in 1906, at Arcade, to 300,000 quarts per day, at the present time, in the ten factories. The output of powdered milk has grown from 2,500 pounds per day, twelve years ago, to a present capacity of 50,000 pounds per day.
“These products include Powdered Skimmed Milk, Butterfat Powders, of varying butterfat content, ‘Cream Powders,’ which contain up to 72 per cent. butterfat, and Powdered Buttermilk.”
—“The ice-cream manufacturer demands a milk or cream product which is clean, which will not sour quickly, which is not a breeder of bacteria, and which gives him the largest percentage of milk solids in proportion both to its bulk and its cost. All these essentials he finds in Merrell-Soule powdered milk. Its powdered form insures the greatest possible purity and cleanness, as is attested by many authorities. There need be no loss through souring, no sticky, half-empty cans standing around, gathering flies and breeding bacteria, when Merrell-Soule powdered milk is used. The ice-cream man makes up just what he needs for the day’s business. He can make up a big supply of cream, for a sweltering day’s run, or a small amount for a cool day. A sudden drop in temperature will not leave him with a lot of cream on hand that must either be used or spoiled. It has been proved that Merrell-Soule powdered milk shows a far smaller bacteria count than any other form of milk, and it offers no breeding place for microbes.
“Merrell-Soule powdered milk can be put to many uses in the ice-cream factory:—
“1. In the production of milk or cream from powdered skimmed milk, butter and water.
“2. The production of skimmed milk from powder and water.
“3. The standardization of the milk solids in the ice-cream batch.
“4. Furnishing the necessary skimmed milk solids.
“5. Blending butter and the powdered skimmed milk with liquid whole milk of any fat content, for the complete total milk solids of the batch.
“Other uses could be mentioned, but these will give the ice-cream maker an idea of the importance of Merrell-Soule powdered skimmed milk in his business.
“Many of the large ice-cream makers are beginning to realize the losses which they incur every year through using condensed milk to raise the per cent of milk solids in their ice-cream.
“By the use of powdered skimmed milk they have an easy and accurate means of holding the solids to any desired percentage.
“Merrell-Soule powdered skimmed milk does not take the place of gelatines, ice-cream powders and the like, which prevent the ice crystals in ice-cream, but it does provide the solids, not fats, which give ‘body and texture’ to the ice-cream and makes it smooth, velvety and palatable.
“Almost every ice-cream maker has his own formula for his mix, which gives the best satisfaction to the trade he serves, and for this reason we will not print any ice-cream formulas. We will be glad, however, to furnish formulas which have given good results, to any ice-cream maker who applies to us.
“In our own experimenting, and in practical work in some of the large ice-cream factories, we have found the powdered skimmed milk to be a wonderful help to ice-cream makers in a great many ways.”
—“The Ekenberg process was invented by Dr. Martin Ekenberg of Stockholm, Sweden. Dr. Ekenberg had experimented with milk drying for some years, and his father, who was an eminent chemist, also, had devoted considerable time to this problem.
[13] This description was given by L. P. Bennett, president of the Ekenberg Co., Cortland, N. Y.
“The Ekenberg process is the result of these investigations, and the machine which Dr. Ekenberg invented, he called the Ekenberg Exsiccator. This consists of a single drum with conical shaped ends, revolving in a vacuum chamber. The milk is introduced into the chamber through various pipes and is sprayed into the conical or bowl shaped ends of the revolving drum,—the drum being heated by steam at a low temperature. The vacuum maintained in the chamber, is from 25 to 27 inches, and as a result, the temperature in the chamber is low, not exceeding 100° F.
“The milk upon being introduced into the bowl shaped ends is evaporated to a considerable degree and then passes off into the suction pipe of a pump, from which the milk is again introduced into the vacuum chamber, this time upon the periphery of the drum, to which it adheres, and is then removed by a series of scrapers or knives. It will be seen that the milk is only upon the drum during about two-thirds of one revolution. The dried product falls into another chamber which is separated from the main vacuum chamber by a series of air locks, so that it may be removed at will from the exsiccator, without stopping the continuous working of the machine.
“When the dried product is removed, its condition is that of light fluffy flakes. It is then allowed to stand in a chamber heated to about 90° F. for about one hour, during which time, the lactose crystallizes. From this chamber it is removed, and then milled in the same manner as wheat is milled in the manufacture of wheat flour.”
—“Ekenflor is the trade name given to the many grades of powdered milk made from skimmed milk, partly skimmed milk, or whole milk. In using Ekenberg Powdered Milk for ice-cream it is not necessary to change the present formulas, but only to adapt then to the use of milk in dry form.
“The raw milk from which Ekenflor is made is drawn from inspected dairies and is manufactured in clean sanitary factories and is therefore of the finest quality.
“Ekenflor does not sour or draw flies, and its use by the ice-cream maker can not fail to reduce the chance of unsanitary conditions in his factory and his losses from spoiled milk.
“There is always ‘a feast or a famine’ in the raw-milk market, and as our powdered skimmed milk keeps almost indefinitely without cold storage, it is always ready for immediate use, no matter how sudden or great the demand may be. Its use makes the ice-cream manufacturer independent of his local supply of milk or cream or condensed milk and of the local prices.”
—For the making of emulsified or homogenized cream, butter is ordinarily employed to supply the milk-fat. Unsalted butter that is clean flavored and made from clean cream is to be desired. If the butter is produced from inferior cream or has any undesirable flavor, the cream made from it will have the same undesirable flavor.
It is the usual practice to store the butter during the period of low prices, which is commonly the summer, and then to use it when prices are high, usually the winter. The question of the kind of butter and method of storage is a very vital one. It is generally considered that sweet cream butter holds better in storage. The temperature of storage should be as near 0° F. as possible.
The successful storing of butter, requires an intimate knowledge both of market conditions and the desired quality of butter for storage. The daily prices and movements of butter, in and out of storage, and the daily receipts in the different markets and the sales, may be obtained from the daily and weekly reports made by the Bureau of Markets, United States Department of Agriculture. In New York City, the market reports are also made in the “Price Current,” published by the Urner Barry Company. Before storing butter, these reports should be studied carefully, to make sure that the market conditions will warrant storage. The quality of the butter can be determined by the market grades or by the actual examining by an expert butter judge. Usually when the ice-cream manufacturer purchases butter for storage, the quality will be determined by the market grade, as personal examination is seldom possible.