Freezing of ice cream also consists of two stages: passing the mixture through a shift (scratch)-the surface of the exchanger with high shear conditions for the full crystallization of ice and air agencies; and the freezing of packaged ice cream in conditions that ensure the rapid freezing and the small size of the ice crystals. Simultaneous freezing and whipping process is one of the most important of typical operations for the development of quality, taste, and output of finished products. Flavouring and colouring can be set as desired, mixture before passing through the barrel of the freezer solid flavoring ingredients, such as nuts, fruits, candy pieces, or ripple sauces, can be added to a semi-frozen products at the outlet from the trunk of the freezer to packing and hardening.
Continuous freezers dominate in the ice cream industry. In this type of process, a mixture of absorbed from flavor tank swept the surface of the heat exchanger, which is faced with liquid, boiling refrigerant (e.g.. ammonia). After switching on the air in the mixture of water in the mixture partially frozen as a mixture of air and combination passes through the barrel of scraped-surface heat exchanger.
Rotating blade knife scrape the ice layer on a surface and dashers keep the product in great excitement, which includes the air phase in the form of small bubbles, and supports discrete ice crystals, as they grow in the volume of the liquid. Residence time for mixing through the annulus freezer varies from 0.4 to 2 minutes, the freezing of prices can vary from 5 to 27C min-1, and draw a temperature of -6C can easily be achieved.
Inclusion of air in ice cream, determined by its " overflow " or increase in volume as a percentage of the volume of the mixture, the need to produce a desirable body and texture. As a guideline, the maximum overflow should be 2.5-3 times the total solids content, to avoid possible defects in the finished ice cream. In older systems, pump configuration resulted in a vacuum, either on the pump itself or on a combination of line of the pump inlet. The air was pushing the spring-loaded, controlled needle valve. New types of freezers use compressed air, which is injected into the mixture. This type of air handling thanks to a system of air filtration prior to the entry into the mixture and better control overrun.
The party of freezing processes differ from continuous systems just described. Trunk party-swept surface of the heat exchanger shirt with the refrigerant and contains a set of dashers and scrapers inside the trunk. It is filled to about half of the liquid, mix. Barrel amounts typically range from 2 to 12 HP freezing and agitators block then activate the product remains in a barrel enough time to achieve the desired degree of excess and stiffness. Whipping increases over time and may not exceed the amount that will fill the barrel of a product (i.e., 100% overrun when you run half full). Batch freezers are used in small industries, where it is desirable to run individual flavored mixture in small scale or keep the element of a " home-style production process. They also operate in a semi-continuous mode for the production of soft serve as a type of desserts. Bunker containing the mixture of feeds barrel as a product will be deleted...