Mix is a term applied to the unfrozen ice-cream. It is sometimes called “batch” or “batter.” The amount of mix prepared at one time may be enough for one or several freezers or for a whole day’s freezing.
—The preparing of the mix is one of the most important phases of the ice-cream business, because of the control of flavor, the effect on the body and texture, and financial considerations.
If the flavors were always uniform, it would be a simple matter to prepare the mix. This not being the case, it requires considerable practice and skill to know exactly how to blend them. The mixer of the different materials should know which must be rejected and which used and in what flavors of ice-cream. The sour or acid flavor can be determined easily in the milk products by means of the acid test. For its use, see Chapter XIV. Besides this, many other undesirable flavors are present in the materials. For example, it would be unwise to try to mix acid fruits with cream already high in acid, since this probably would cause a pronounced sour taste and might curdle the cream. Some makers believe that the flavor added to the ice-cream will cover up any bad flavors in the milk products, but this is not the case. If there is any undesirable flavor in the materials it can be detected in the ice-cream. Of course the person preparing the mix has the receipt or formula but this is only a general guide; the final test is the taste. Each mix should be tasted before it is frozen to make sure that the flavor is correct. If not palatable in the mix, it will not be in the ice-cream. In some cases, it is necessary to have the flavor more pronounced in the mix than is desired in the finished product because the flavor may freeze out or become less pronounced.
From the financial viewpoint, mixing is one of the most important parts of the whole enterprise. Here the question of whether the business is to be a success or failure is largely determined by the cost of the materials. After the materials have been determined, it is necessary to see that the exact amount is used in each mix. This means that each mix must be standardized, both for fat and total solids. For method of standardization, see Chapter XIV. An example may illustrate what a small loss will amount to in dollars and cost a gallon. Suppose 1000 pounds of cream testing 20 per cent fat were desired and instead of this it tested 20.5 per cent fat. This would use 5 pounds more fat which at $1.00 a pound would equal $5.00; the wages for a good man. This 1000 pounds of cream would make approximately 250 gallons of ice-cream. The $5.00 additional cost for 20.5 per cent cream would make the ice-cream cost 2 cents a gallon more. This shows that a small divergence in cost a gallon may make a big total difference especially noticeable if near the dividing line between profit and loss. Another example indicates how carefully the mix may be standardized to reduce cost. An ice-cream plant found that the mix could contain .21 per cent of acidity without injury to the quality of the product. Each material was tested for acidity (see Chapter XIV), and because there was an abundant supply of buttermilk for which there was no market, the mix was standardized to .21 per cent acidity by the use of buttermilk. This reduced the cost by using a material for which there was no market. The body and texture are largely determined by the materials employed, although the freezing and subsequent handling has a decided influence on the quality.
Too much study cannot be given to the question of the materials to be used in the mix nor too much pains taken to see that each mix is properly standardized.
—Much detail variation in preparing the mix is possible and yet obtain accuracy and good quality of ice-cream. The usual procedure is as follows: The milk products are first put into the container in which the mixing is to be done. In a large ice-cream plant some type of the mechanical mixer, Figs. 20, 21, 22, 23, and 24, is used. A view of a mixing-room is shown in Fig. 51. The mixers are just above the level of the floor, making it easy to put materials into them. In this case, the mixers are above the freezers so that the mix flows by gravity. Each material should be weighed or measured accurately. After the materials are mixed together, it is often desirable to test them to make sure that the desired standardization has been obtained. The sugar is weighed next into the mix. The amount will vary according to the flavor and materials used. For example, with sweetened condensed milk, less sugar will be required. Time should be allowed before freezing for the sugar to dissolve. This can be hastened by stirring, which may be done by a mechanical or hand agitator, depending on the size of the mix. Whichever method is employed, care should be exercised not to stir the mix enough to cause the fat to churn. This would cause lumps of fat or butter in the ice-cream.
Fig. 51.—Mixing room in large ice-cream plant.
The stabilizer is added next. In some cases, such as the prepared ice-cream powders, it should be mixed with the dry sugar and added with it. If gelatine or gum tragacanth is used, it should be applied slowly and the mix agitated to prevent lumps forming. For method of preparing gelatine, see Chapter IV. If color is desired, it should be put in just before the flavor. This will prevent streaks in the ice-cream. Lastly, the flavor should be added, care being taken to use the exact amount. In the case of fruit ice-cream, the fruit may not be put in until the mix is partly frozen. If acid fruits are stirred in the mix before partly freezing, the cream might curdle. If the fruit is added to the mix and then frozen in an upright freezer, there is danger of it settling to the bottom.
If it is desired to emulsify or homogenize the whole mix, this should be done before the flavoring materials are added. The flavoring might be lost during the process and pieces of fruit would clog the machine.
When ready to freeze, the mix should be tasted to make sure that everything has been added and that the mix has the proper flavor. Of course little can be told about the body and texture of the resulting product by tasting the mix. But the flavor is a good index of that of the ice-cream.
—As will be pointed out in connection with over-run, the temperature of the mix when it enters the freezer is very important. If too warm, the cream will churn before it will beat up or whip. Most of the mechanical mixers possess some means of controlling the temperature of the mix. But the operator should make sure that the mix is at the desired temperature. It should never enter the freezer above 60° F. and the nearer 40° F. the better.