In this case a mixture composed of 20/35 cream and 15/35 skim milk will test 20 per cent. = Another method of standardizing that is quite simple and accurate and involves but little figuring is as follows: Multiply the amount of cream by the difference between its test and the required test, and divide the product by the difference between the required test and the test of the milk to be added. Example: Standardize 120 pounds of 30 per cent. cream to 20 per cent., using 4.2 per cent. milk. 30 20 10, which is the difference between the test of the cream and the required test. 20 4.2 15.8, which is the difference between the required test and the test of the milk to be added. Using these figures we have 120 X 10÷ 15.8 or 120 x 10 =75.95. Therefore, 75.95 pounds of 4.2 per cent. milk are required to reduce the test of 120 pounds of 30 per cent. cream to 20 per cent. The accuracy of this method is shown by the following figures: X 15.8 Therefore 195.95 lbs. 20% cream contain 39.19 lbs. fat. Either of these methods will be found valuable as aids in regulating the quality of the ice cream produced. Standardizing the ice cream mixture. It is also very important that the ice cream maker should know how to calculate the per cent. of butter fat a given mixture will contain. In addition to that it is necessary to know the amount of butter fat in the mixture in order to find the cost of a gallon of ice cream. In making these calculations it must be remembered that the sugar, flavoring, gelatin and other in gredients reduce the test just the same as skim milk would. The following example will make this clear. 20 lbs. 17% cream 4 lbs. sugar 2 oz. gelatin 244 lbs. of mixture The 20 pounds of 17 per cent. cream contain 3.4 pounds of butter fat, which represents the total fat content of the ice cream mixture. To determine the per cent. of fat in the mixture, divide the pounds of butter fat by the total weight of the mixture and point off two places for per cent. = In the following mixture the cream is not the only source of fat, but the method of procedure is the same. 12 lbs. 24% cream 4 lbs. condensed milk testing 8% fat 4 lbs. whole milk testing 4% fat 4 lbs. sugar 2 oz. flavor 24 lbs. 2 oz. of mixture 12 lbs. 24% cream contain 2.88 lbs. fat 4 lbs. 8% condensed milk contain .32 lbs. fat 4 lbs. 4% milk contain .16 lbs. fat 3.36 lbs. fat in the mixture 3.3624.125 = 13.93% of fat in the mixture. To find how rich cream must be used to give a mixture of a certain test, multiply the pounds of ice cream mixture by the desired test of the mixture, divide the product by the weight of the cream to be used, and point off two places for per cent. Example: What per cent. of butter fat must the cream contain to give a mixture testing 9 per cent.? Calculating on the basis of a mixture for ten gallons of ice cream we would need 44 pounds of cream, eight pounds of sugar, four ounces of flavor and four ounces of gelatin, giving a total weight of 521⁄2 pounds. = Since none of the ingredients except the cream contain butter fat, the entire 4.725 pounds will be contained in 44 pounds of cream; therefore, 4.72544 10.74%, which represents the per cent. of butter fat which the cream must contain. The accuracy with which the work is carried out should be checked up from time to time by testing the mixture for fat. Testing for fat in ice cream by the Babcock method presents some difficulties owing to the presence of the sugar. A fair test may be obtained by following the same directions as for cream, except that a little less acid should be used and it must be added a little at a time. Even with the utmost care there is usually a larger or smaller amount of black material below or distributed through the fat which makes an accurate reading very difficult. The use of special acids. By using a mixture of equal parts of glacial acetic and hydrochloric acids instead of sulphuric acid, there is less danger of charring the sugar. In making the test mix the sample of ice cream thoroughly and weigh nine grams of the sample into a cream test bottle. Fill the bottle almost to the neck with the acid mixture and shake it until the ice cream and acid are well mixed. Place the bottles in hot water until the mixture turns black. The bottles are then whirled in the Babcock centrifuge and the test completed as for cream. NOTE: For complete standardizing tables see Appendix. CHAPTER VIII PREPARING THE ICE CREAM MIXTURE The method of procedure in preparing the ice cream mixture will vary more or less with the different kinds and flavors of ice cream. The ice cream maker should therefore have a clearly defined idea as to the results desired and then select and put together such ingredients as will give these results. The various ingredients should be weighed or measured very exactly, as it is only in this way that uniform. results can be obtained. Selecting the cream is one of the first considerations. In order to make a high grade ice cream, it is very important that the cream and milk used be of good quality. This implies a freedom from foreign odors and flavors, a sufficiently high per cent. of fat, and an acidity of not over 0.25 per cent. The objections to foreign odors have already been mentioned.1 It has been pointed out that there is but one way to look at such defects, and that is to consider them very objectionable. The acidity of the cream, however, is not always such a serious defect. In fact, if the fermentation taking place in the cream is purely of an acid nature and has developed to a point where it is just noticeable to the taste, the excess acid can be neutralized by the addition of viscogen or sodium hydroxide, and an equal amount of fresh sweet cream 1 See page 2. |