ice cream well packed so that it will not be necessary to return unsold ice cream. The ice cream when returned to the factory is usually very soft or even in a melted condition. In this melted ice cream the bacteria grow rapidly. If the cream used in its manufacture has been pasteurized, the fermentations taking place in the melted ice cream are not likely to be of an acid nature, because of the destruction of the lactic acid bacteria in the pasteurizing process. The bacteria present in the old ice cream are more apt to be of the type that feed upon proteids. It has been pointed out that the cleavage products of proteids are sometimes poisonous. Hence, the proteolytic fermentations taking place in the old ice cream may be of a dangerous nature, particularly if the ice cream contains a poor grade of gelatin. Unclean utensils introduce into the ice cream large numbers of bacteria of the most undesirable sort. Every precaution should be taken to have all utensils properly cleansed and sterilized. Shipping cans having deep crevices along the seams or roughened places, due to improper tinning on the inside, are very difficult to keep clean. Such cans should be retinned and the seams flushed with solder. The cans will then be easy to clean. Hot and cold water for washing and rinsing must be available at all times. Sterilizing may be done with hot water but a steam jet is more satisfactory. With the proper facilities for cleaning and sterilizing utensils, the number of bacteria in ice cream, coming from the utensils, should be very small. CHAPTER III THE CARE OF MILK AND CREAM AT THE FACTORY The proper handling of milk and cream as soon as it reaches the factory is of utmost importance in the ice cream business. Each can of inferior cream received, or allowed to spoil after reaching the factory, means a cut in the profits of the business. In order to prevent losses of this sort and to insure the keeping qualities of the cream as well as the purity of the ice cream made from it, some provision must be made for receiving, sampling, and grading the raw material as it comes to the factory. The sampling and grading must be followed by thorough pasteurization and cooling to insure the best results. Receiving. As each shipment of milk or cream reaches the factory it should be weighed, sampled, and graded. Each patron's shipment should be weighed separately and tested for butter fat by the Babcock method, so that payment may be made on the butter fat basis. Payment on this basis is more businesslike than the old method of buying cream at so much per gallon. It also prevents losses to the factory and at the same time does exact justice to each patron, provided the sampling and testing are properly done. Sampling. Each can of milk or cream should be thoroughly stirred before the sample is taken. The sample may be taken with a long-handled sample dipper, with a milk thief, or a McKay sampler, if a composite sample is to be taken. For milk tests a composite sample may be taken, and the test made two or three times a week. A composite sample is a sample made up of small amounts of milk taken from a number of shipments. Such a sample should represent the average quality and proportionate amount of the whole. This system of sampling is quite satisfactory for milk. For cream, it is much more difficult to get even a fairly accurate composite sample, because the viscosity of the cream makes it difficult to measure out an exact amount. A slight variation in the amount taken from one shipment may introduce quite an error on account of the high percentage of butter fat in cream. For this reason each patron's cream shipment should be tested separately. A B C Fig. Testing. The method of testing cream for fat involves no great variation from the method followed in testing milk. The only precautions that need be mentioned here are the weighing of the samples, manner of reading the test, and the temperature at which the test is read. It is necessary to weigh into the test bottle the exact amount of cream necessary for testing, because a pipette will not deliver an exact amount. In the first place, the fat content of cream is variable, and the specific gravity of the cream varies with the fat content. More or less air is also incorporated with the cream in passing through the separator and cannot escape on account of the viscosity of the cream. On account of this viscosity more cream adheres to the inside of the pipette also. For these reasons a fair test cannot be made without weighing the exact amount of cream. For this purpose quite a sensitive balance must be used. All the other operations of the test are the same, except in the reading of the fat column. The proper points from which to read cream tests are illustrated in Fig. 13. It will be noticed that the milk tests are read from the extreme bottom of the fat column to the extreme top, whereas the cream test is read from the bottom of the fat column to the bottom of the meniscus. The reason for this difference is that in a whole milk sample there are some fat globules too small to be separated by centrifugal force; therefore, the fat which is not separated is compensated for by giving the fat column a more liberal reading. In reading either milk or cream tests care must be exercised to have the tests at the correct temperature. The temperature at which these tests should be read is 140° F. Since the fat column will contract or expand |