A continuous ice cream freezer freezes ice cream mix into a semi-solid state using a cylindrical barrel surrounded by a refrigerant. Here's a breakdown of the process:
The Core Components
The essential components of a continuous ice cream freezer include:
- Freezing Barrel: A cylindrical barrel, typically made of stainless steel, through which the ice cream mix flows.
- Refrigerant Jacket: An outer concentric cylinder surrounding the barrel. This jacket contains a refrigerant (like ammonia or Freon) to cool the barrel.
- Scraper Blades (Dasher): Rotating blades inside the barrel that scrape the frozen ice cream off the inner surface and mix air into the mix.
- Mix Inlet and Outlet: An inlet to introduce the liquid ice cream mix into the barrel and an outlet for the frozen ice cream.
- Air Injection System: A mechanism for injecting air into the mix during freezing.
The Freezing Process
- Mix Entry: The liquid ice cream mix is pumped into the freezing barrel at a controlled rate.
- Refrigeration: The refrigerant in the surrounding jacket cools the barrel to a low temperature.
- Freezing and Scraping: As the mix flows through the barrel, the cold surface causes it to freeze. The scraper blades (dasher) continuously scrape the frozen ice cream from the barrel walls. This prevents the formation of large ice crystals and ensures a smooth texture. The scraping action also incorporates air into the ice cream.
- Air Incorporation (Overrun): The injection of air into the ice cream mix, referred to as overrun, increases the volume of the ice cream. Overrun is carefully controlled to achieve the desired texture and density.
- Discharge: By the time the mix reaches the end of the barrel, it has been frozen to a semi-solid or plastic state with the desired overrun. The finished ice cream is then discharged from the outlet.
Key Features and Control
- Continuous Operation: The process is continuous, allowing for high production volumes.
- Temperature Control: Precise temperature control of the refrigerant is crucial for optimal freezing and texture.
- Overrun Control: Control of the air injection rate determines the overrun and the final density of the ice cream.
- Flow Rate Control: The flow rate of the mix through the barrel influences the freezing time and crystal size.
In essence, the continuous ice cream freezer provides a highly efficient method for large-scale ice cream production by combining rapid freezing with air incorporation and continuous operation.
