The size and kind of equipment will depend on the extent of the business and the available capital. It is not considered economical to install a mechanical refrigerating system unless at least seventy-five gallons of ice-cream are manufactured a day.
Certain factors should be considered when purchasing machinery; the construction and adaptability of the machine for the type of work it is intended to do; the ease of making repairs; the ease of cleaning; the durability of the machine; the protection to gearing from ice and salt.
Fig. 8.—Hand freezer with tub and can cut away showing ice and salt mixture and beaters and scrapers in the can.
Fig. 9.—Hand freezer with fly wheel, using salt and ice mixture for freezing. The capacity is five gallons.
Fig. 10.—Power driven tub and can freezer, using a salt and ice mixture. The can, dasher, cover and gears are shown removed.
Fig. 11.—Horizontal brine freezer attached to salt and ice brine box. The pump is behind the box.
—The general principle of the ice-cream freezer is the same in all makes; however, the application may be varied. The unfrozen ice-cream or mix is placed in a container, usually called the freezing-can. This can is surrounded by the freezing material, either cold circulating brine or an ice and salt mixture. In the can is the beater or dasher. To this is attached two scrapers which, when rotated, scrape the frozen ice-cream from the sides. The can itself may revolve or stand still, depending on the type of freezer. The dasher may revolve or stand still, depending on whether the can revolves or stands still. In most freezers there is another part of the dasher which revolves to help beat up the ice-cream. The freezers may be divided into two general classes. The one class consists of a tub and can in which an ice and salt mixture is used between the tub and can. This type of freezer is made to run by hand or mechanical power, and varies in size from a few pints to ten gallons. The largest hand size is usually five gallons; these have a flywheel. The types of hand freezers are shown in Figs. 8 and 9. A power-driven tub and can freezer, using a salt and ice mixture in the tub for freezing, is shown in Fig. 10. The other class is the brine freezer. In this, cold brine is forced around the freezing-can. The freezer runs by mechanical power, either belt-driven or directly connected to an electric motor. The brine may be made from an ice and salt mixture, or it may be cooled by an artificial refrigerating system. There are two general types of brine freezers. One has the freezer in a horizontal position and the other in a vertical. Advantages are claimed for both. The arrangement of brine freezers when the brine is obtained from a salt and ice mixture is shown in Figs. 11 and 12. The brine as it comes from the freezer is sprayed over the ice and as it trickles through is cooled again. It is then pumped around the freezer again. The ice is held in the box by means of a heavy wire screen; otherwise, it would clog the pump.
Fig. 12.—Vertical belt driven brine freezer connected to ice and salt brine box. Pump is shown between freezer and box.
Fig. 13.—Perfection brine freezer, direct motor drive.
Some of the types of brine freezers in common use are shown in Figs. 13, 14, 15, and 16. Most of these may be either belt or direct motor-driven. The usual size is ten gallons. In some cases they have been made larger but these are not in common use. It is the usual practice to have a supply tank just above the freezer-can which can be filled, while one can is freezing. The mix for the next freezer is placed in this supply can and will then run quickly from it into the freezer.
Fig. 14.—Progress vertical belt drive brine freezer.
Fig. 15.—Emery Thompson vertical direct motor drive brine freezer.
Another brine freezer is the disc which may be used either as a batch or continuous freezer. A front view of this is shown in Fig. 17. The supply can is seen on one side and the delivery spout on the other. A glass plate over the freezing discs allows the process to be seen at any time. A side view is seen in Fig. 18, showing the brine box and pump. The freezing discs are illustrated in Fig. 19, also the scrapers to remove the ice-cream from the discs and the screw to force the ice-cream along. When used as a batch freezer, the ice-cream is drawn from the bottom.
Fig. 16.—Fort Atkinson horizontal belt drive brine freezer.
Fig. 17.—Disc brine freezer either continuous or batch.
Fig. 18.—Side view of freezer shown in Fig. 17. Arrangement of brine tank and pump are shown.
Fig. 19.—Freezing discs of freezer shown in Figs. 17 and 18. The scrapers for removing the ice-cream from the discs and the screw to force it out of the delivery spout are shown.
Fig. 20.—A pasteurizer or ripener used as an ice-cream mixer. Strips are attached to the coils to prevent the settling of the sugar on the bottom.
—When large quantities of ice-cream are made, a container of some sort, with a mechanical agitator to stir the contents, is used to mix the ice-cream ingredients. Some of these mixers are provided with coils in which water or brine may be circulated to control the temperature. Some may be operated as a pasteurizer. An ordinary cream ripener might be used as a mixer if the sugar could be prevented from settling to the bottom. Some manufacturers have accomplished this by placing a strip of iron on the coils which will reach almost to the bottom of the ripener. Such an arrangement is shown in Fig. 20. An ordinary starter can might be utilized as a mixing vat or can. (Fig. 21.)
Fig. 21.—Minnetonna starter can or ice-cream mixer.
A number of ice-cream mixers are commonly used, as shown in Figs. 22, 23, and 24. Most of these have coils which carry cold water or brine to cool the mix. In some these coils act as the agitator and in others they are placed in a jacket around the mixer. In order to keep the materials properly mixed if the coils themselves do not serve as the agitator, there is some form of mechanical agitator. These agitators may be belt or direct motor-driven.
—In most plants where much ice-cream is made, a special kettle is employed to dissolve the gelatine. (Fig. 7.) This consists of a copper steam-jacketed kettle. With this the gelatine and water may be heated without danger of burning. The size of these kettles depends on the amount of gelatine used.
—Some means of keeping the ice-cream cold after it is removed from the freezer must be provided. This may be a specially cooled room known as a hardening room or the ice-cream may be packed in a mixture of salt and ice. These methods of hardening will be discussed later.
Fig. 22.—Alaska ice-cream mixer. The side is cut away showing the coils and insulation. The mechanical agitator is seen at the bottom. By means of the tight fitting cover and the air pump, the mix may be forced to the freezer by air pressure.
Fig. 23.—Wizard ice-cream mixer.
Fig. 24.—Emery Thompson ice-cream mixer.
—In order that the freezer may be kept in use, as soon as the ice-cream is sufficiently frozen, it is removed and placed in other cans to harden. These are known as packing-cans (Fig. 25) and are made of heavy iron and tinned and fitted with a cover. The cans vary in size from one quart to five gallons and the ice-cream is hardened and delivered in these. When ready for delivery, these pack-cans are placed in tubs which should be a little higher than the pack-can to allow for ice over the top. There should be a space also of 2-4 inches between the sides of the can and the tub to allow for the ice and salt. The ice-cream may be packed in small oblong containers known as bricks, usually containing one or two pints.
Fig. 25.—Two types of ice-cream packing-cans.
The ice-cream may be hardened in a larger brick mold which will make several smaller bricks. When hard the ice-cream is cut into the smaller bricks, wrapped in parchment paper and placed in a paper carton. This is the usual method of handling brick ice-cream. Several different layers may be placed in each brick.
—The ice must be broken into small pieces for freezing or packing the ice-cream. This may be done by hand with an ice spud or cracker. (Figs. 26 and 27.) If much ice is to be cracked or crushed, a mechanical crusher should be used. (Fig. 29.) The small ones run by hand power but turn rather hard. The crushers run by mechanical power are more frequently seen in ice-cream plants. These vary in size.
Fig. 26.—Ice spud.
Fig. 27.—Ice cracker.
Fig. 28.—Perforated ice shovel.
Fig. 29.—Ice crusher with tight and loose pulley for mechanical power. The teeth or picks on the drum may be seen.
Fig. 30.—The perfection ice-cream can-washer and sterilizer.
—The washing of the ice-cream pack-cans by hand in an ordinary sink consumes much time. In the larger plants an ice-cream can-washer is used. This consists of sprays of water and revolving brushes. The cans are usually brushed both on the inside and outside. Some types of ice-cream can-washers and sterilizers are shown in Figs. 30 and 31. When washed, the cans should be sterilized.
Fig. 31.—Fort Atkinson ice-cream can-washer and sterilizer.
Fig. 32.—De Laval centrifugal emulsor.
—These machines vary considerably in mechanical construction as shown in Figs. 32, 33, 34, 35, and 36. Nevertheless, the making of cream from butter, milk powder, condensed milk or skim-milk is accomplished by each machine. The force used to break up and mix the materials varies with the different machines. One type which uses steam as the force to break up the material is illustrated by Fig. 33. The amount of steam pressure required varies with the different makes. Another type of machine which uses centrifugal force as the means of breaking up the materials is illustrated by Figs. 32 and 36. In this type, the materials are broken up or mixed by being thrown by centrifugal force through a very small opening or narrow space. The other type of machine, which is operated by valve pumps, is illustrated in Figs. 34 and 35. By means of the pumps the materials are forced through a very small opening against some hard material. This machine, known as a homogenizer, breaks the materials into very small particles; for example, cream that has been homogenized cannot be re-churned in butter because of this. A good quality of cream may be made from any of the following combinations according to the DeLaval Separator Company:
Skim-milk powder—water—butter—(preferably uncolored and unsalted).
Whole-milk powder—water—butter.
Condensed skim-milk—water—butter.
Condensed whole milk—water—butter.
Skim-milk—skim-milk powder—butter.
Skim-milk—condensed skim-milk—butter.
Whole milk—skim-milk powder—butter.
Whole milk—condensed skim-milk—butter.
Fig. 33.—Perfection cream-maker and emulsifier.
Fig. 34.—Progress homogenizer.
Fig. 35.—Gaulin homogenizer.
One should never lose sight of the fact that the better the quality of the materials used, the better will be the flavor of the cream. It is impossible to make first-quality cream from poor materials. The whole milk and skim-milk must be clean and sweet. Skim-milk powder should be dry, loose, and fluffy. The condensed milk should be clean flavored and fresh. Off-flavored condensed milk or milk that is grainy or gritty should never be used. The manufacturers of the various machines send specific directions for their operation. To insure success, these directions should be followed carefully. It is the usual practice first to put the milk powder into solution, then to cut the butter into small pieces and put it into the milk. If skim-milk is used, the butter is put directly into it. The milk and butter are then heated to a temperature high enough to melt the butter, usually 130° to 150° F. It is then run into the machine. Because of the tendency of the butter to rise to the top, the materials must be kept in constant agitation until run into the machine. Otherwise, the butter would be at the top and would not run into the machine until the other materials had all run through.
Fig. 36.—Sharples centrifugal emulsor.
Some makers emulsify or homogenize the whole ice-cream mix. In this case, the flavoring extracts and fruits are not added until after the mix has been through the machine. It is the general opinion that the emulsifying or homogenizing of the whole mix makes a smoother body and texture in the product.
Advantages in the use of emulsors and homogenizers:
1. Smoother body in ice-cream.
2. Less time required for ageing cream, especially pasteurized.
3. Not necessary to carry so large a stock of raw materials.
4. Ice-cream of more uniform composition.
Disadvantages in the use of emulsors and homogenizers:
1. The disadvantage in the use of the homogenizer is in its abuse since a homogenized cream will appear richer than it really is. There is a tendency to use less solids, especially fat.
2. Danger of using inferior materials.
3. If cream is not needed for ice-cream and has been homogenized, it cannot be churned.
—Because of the constant change in price, it is impossible to give even estimates of cost of equipment. The price might be correct to-day and incorrect to-morrow. The cost of equipment based on the gallonage of ice-cream is usually higher for the smaller plant. In order to obtain accurate prices, the various dairy supply houses should be consulted.