Other pieces of equipment which have added to the completeness of the ice-cream factory are the Mojonnier milk tester, introduced to the trade in 1915; the Mojonnier ice-cream overrun tester, introduced in 1917; the 80-quart ice-cream freezer, introduced by the Creamery Package Manufacturing Co. in 1917; the Mojonnier icecream packaging machine, which appeared in 1920; and the Sealright ice-cream filling machine, 1920.

TRADE PAPERS AND BOOKS.

The Ice Cream Trade Journal made its appearance in 1905 and was followed by the Ice Cream Review in 1916. In addition to these, several journals such as the International Confectioner and some of the dairy journals have devoted space to the manufacture of ice cream. The ice-cream publications have kept up to a high standard, and by presenting high ideals as well as technical knowledge, have done their share in bringing about rapid progress in the ice-cream industry.

In 1883 an interesting book entitled "Ice Cream and Cakes" was copyrighted by Chas. Scribner's Sons, New York. The author evidently feared criticism, as he signed himself "An American." It is true that he was not in possession of the scientific facts which are available to-day, yet he was well informed and a great deal ahead of the ice-cream manufacturers of his time. Later books were published by manufacturers. These are Ice Cream and Candy Maker's Factory Guide, by the Horizontal Freezer Co., of Chicago; Heller's Guide for Ice Cream Makers, by B. Heller & Co., Chicago; and Bottler's and Ice Cream Maker's Handy Guide, by WarnerJenkinson Co.

The first college textbook giving instruction in the manufacture of ice cream was "Dairy Technology," by Prof. C. Larson and Wm. White, published by John Wiley & Sons in 1913. This was followed by a textbook dealing exclusively with the manufacture of ice cream and ices by Prof. J. H. Frandsen and E. A. Markham; it was published by the Orange Judd Co. in 1915. The latest book on the subject is entitled "The Book of Ice Cream," by Prof. W. W. Fisk, and was published by the MacMillan Company in 1919.

THE STATE AGRICULTURAL COLLEGES.

Instruction in ice-cream making was offered as early as 1892 at the Pennsylvania State College. The Iowa State College was the next one to offer such instruction, but not until 1901. After that the other State colleges followed in rapid succession, until ice-cream manufacture is to-day offered in 30 State colleges which give fairly thorough and scientific instruction to from 600 to 700 students annually. In addition, many of our colleges are offering short courses in ice-cream making, from one to two weeks in duration; and most of them are also giving some ice-cream instruction in the general and more elementary courses offered to all agricultural students. It is evident that this work has been of some importance to the industry,

as improvement in the technique can be made only by men of thorough technical training.

TABLE 3.-College instruction offered in the manufacture of ice cream.

Nineteen agricultural experiment stations and the Dairy Division in Washington, D. C., report that they are carrying on experimental or research work on problems related to the ice-cream industry. These stations are as follows: California, Connecticut, Idaho, Illinois, Indiana, Iowa, Kansas, Maryland, Minnesota, Mississsippi, Missouri, New York, Pennsylvania, Texas, Utah, Vermont, Virginia, Washington, and Wisconsin.

It is natural that experiment-station bulletins published on problems related to the ice-cream industry are as yet not very numerous; it can be said, however, that we have made a good start and such publications will doubtless become much more numerous in the future.

The Government and experiment-station bulletins published up to date are:

Dairy Division, United States Department of Agriculture.

Department Bulletin 303. A bacterial study of retail ice cream, 1915. Department Bulletin 563. The determination of bacteria in ice cream. 1917. Department Bulletin 1123. Proportioning the ingredients for ice cream and other frozen products by the balance method. 1922.

Department Bulletin 1161. Effect of composition on the palatability of ice cream. 1923.

Reprint from Journal of Agricultural Research, Vol. XXI, No. 10. Sandy crystals in ice cream; their separation and identification. 1921.

Vermont Agricultural Experiment Station.

Bulletin 155. Principles and practice of ice cream making. 1910.

Wisconsin Agricultural Experiment Station.

Bulletin 241. An ice cream overrun test. 1914.

Bulletin 262. Ice cream making. 1916.

Illinois Agricultural Experiment Station.

Circular 219. Conserving sugar in ice cream manufacture. 1918.

Circular 256. Does carbon dioxide in carbonated milk and milk products destroy bacteria?

1922.

Nebraska Agricultural Experiment Station.

Bulletin 168. Sugar saving substitutes in ice cream. 1918.

Connecticut Agricultural Experiment Station.

Bulletin 83. The bacterial content of ice cream. 1915.

New York Agricultural Experiment Station.

Memoir 18. A study of bacteria in ice cream during storage. 1919.

Virginia Agricultural Experiment Station.

Technical Bulletin 7. Smoothness and keeping qualities of ice cream as affected by solids. 1915.

Bulletin 211. Effect of binders upon the melting and hardness of ice cream. 1916.

Iowa Agricultural Experiment Station.

Bulletin 123. Classification of ice cream and related frozen products. 1911. Bulletin 118. Lacto. 1911.

Bulletin 140. Lacto, a frozen dairy product. 1913.
Bulletin 174. Bacteria in ice cream.

1917.

Bulletin 180. Factors which influence the yield and consistency of ice cream. 1918.

Bulletin 186. A bacterial study of the method of Pasteurizing and homogenizing the ice-cream mix. 1919.

The Journal of Dairy Science, a publication of the American Dairy Science Association, first appeared in 1917. This journal has published several articles relating to the ice-cream industry; the data presented in these are usually the result of work carried on in some of the experiment stations.

Scope of work considered by the experiment stations.-The first bulletin published on ice-cream making, Bulletin No. 155, Vermont Station, was naturally very general. It gave a complete discussion of the general methods of ice-cream making and was based on valuable experimental data. This bulletin was so complete that it was even used as a textbook in some of the colleges. The first experimenters naturally sought to establish some of the fundamentals. They invariably presented a score card for ice cream and a classifi

cation.

77612-24- -31

Several score cards have been suggested for ice cream, but none of these were approved by the American Dairy Science Association, and in 1920 that organization appointed a committee to prepare an official score card. The following score card was recommended by that committee and was adopted as the official score card, October 11, 1921:

It is recommended in Bulletin No. 155, Vermont, that ice cream. may be classified as, first, plain ice cream, frequently known as Philadelphia, and second, French, or Neapolitan, ice cream, which differs from the first in that it contains eggs. Iowa Bulletin 123 contains the following classification:

I. Plain ice creams.
II. Nut ice creams.
III. Fruit ice creams.
IV. Bisque ice creams.
V. Parfaits.

VI. Mousses.

VII. Puddings.

VIII. Aufaits.

IX. Lactos.
X. Ices.

1. Sherbets.

2. Milk sherbets.
3. Frappés.

4. Punches.

5. Soufflés.

Prof. W. W. Fisk, in his textbook entitled "The Book of Ice Cream," combines the two, and has proposed a very sensible classification. An official classification should be adopted by the American Dairy Science Association.

MANUFACTURING METHODS.

Certain facts concerning the manufacture of ice cream have been reasonably well established. It has been determined without doubt that there is a rather definite relationship between the composition and the palatability of ice cream. The conclusions reached in the experiments carried out by the Dairy Division are in harmony with results obtained by a commercial concern conducting experiments along similar lines. It should therefore be understood that it is not possible to make a really palatable ice cream without making it from cream. Ice cream has been standardized reasonably well and contains usually from 20 to 22 per cent milk solids. The sugar is somewhat more variable, ranging from 12 to 16 per cent in different brands of ice cream.

Body and texture defects of ice cream have been studied and to some extent solved. It has been definitely proven that sandiness in ice cream is due to the crystallization of lactose from a supersaturated solution. It has been found that there is a somewhat definite relationship between the temperature at which the ice cream. is drawn from the freezer and the texture and yield of the resulting product. The time required for freezing bears a similar relationship to the texture and yield.

By increasing the viscosity of the mix, especially by the addition of binders and by homogenization, the air can be worked into the

ice cream in a finer state of division. Therefore the mix becomes more finely divided and the ice crystals in the finished product are decreased in size correspondingly. The body of the ice cream also becomes firmer and stronger as the pressure within the air cell increases with the decrease in the size of the cell.

In unpublished work done at the Iowa State Experiment Station it has been found that the greatest factor responsible for the increase in viscosity by homogenization is the clumping together of the fat globules. As the pressure of the homogenization is increased the fat clumps increase in size and there is a somewhat corresponding increase in viscosity. It has been found that if an ice-cream mix homogenized at a higher pressure is stirred or agitated the clumps. of fat globules are reduced in size, and this is accompanied by a corresponding decrease in viscosity.

The data that have been secured on the bacteriology of ice cream show that this product frequently contains excessive numbers of bacteria, but by using suitable raw materials and careful methods the counts can be kept low and will remain low during proper storage. The investigational work at present being done deals mainly with the question of the sanitary quality of the product. Bacterial standards are in force in a few cities and will undoubtedly be much more common in the near future. With the establishment of such standards the factors influencing the bacterial count become highly important; chief among these are, the quality of the raw materials used, the pasteurization of the cream or mix, the storage of the cream or mix, methods of cleaning equipment, and the holding of ice cream. The bacteriology of ice cream is comparatively simple and involves keeping out microorganisms as much as possible and the destruction or prevention of growth of those that do gain

entrance.

The ice-cream field offers great opportunities for future research, but the person choosing that field should be well trained, especially in physical chemistry. The field for the bacteriologist and dairy chemist is somewhat limited; most of the future problems will be physical and there should be a wonderful opportunity for the man possessing the necessary qualifications to develop that phase of our dairy research.

SUMMARY.

It is the general belief that ice cream was first made in Italy. It was possibly introduced into France about 1550. The earliest printed record of ice cream in England is found in the Experienced English Housekeeper, published in 1769. The first advertisement of ice cream in the United States appeared in a New York paper, the Post Boy, June 8, 1786. The first wholesale ice-cream business was started by Jacob Fussell in Baltimore in 1851.

The ice-cream business increased in the United States from 80,000,000 gallons in 1909 to 263,529,000 gallons in 1922. The factors responsible for this remarkable progress may be summarized as follows: (1) The progressive and aggressive attitude of the icecream manufacturers. (2) The rapid development and improvement of machinery and equipment. (3) Trade papers and books.