Cryogenic Freezing Quiz: Advantages and Disadvantages

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Questions and Answers

What is an advantage of cryogenic liquid freezing?

Low product weight loss during freezing (correct)

High maintenance cost

Dependence on many cryogenic liquid suppliers

Low cryogenic liquid consumption

What is a disadvantage of cryogenic liquid freezing?

High floor space required

Low initial capital

Cryogenic liquid is inexpensive

Cryogenic liquid is expensive (correct)

How is ice formed in a tube ice machine?

Water is spread on a belt and frozen

Water is frozen in a jacketed cylinder

Water is frozen in a vacuum chamber

Water is distributed on the inner surface of a vertical tube (correct)

What is the purpose of the knives or similar devices in ice manufacturing?

To scrape the ice formed on the jacketed surface Signup and view all the answers

What is the temperature in the vacuum chamber where ice is formed?

-3°C Signup and view all the answers

What is the advantage of cryogenic liquid freezing in terms of space?

Low floor space required Signup and view all the answers

What is the primary function of Shell and Coil Equipment?

To cool water and drinks rapidly Signup and view all the answers

What is the benefit of applying a vacuum in Vacuum Cooling Equipment?

To reduce the cooling time Signup and view all the answers

What is the primary purpose of Combined Cooling with Mixing Recirculation?

To mix and recirculate products efficiently Signup and view all the answers

What is the most critical factor in freezing foods?

All of the above Signup and view all the answers

What happens when large ice crystals form during freezing?

The cell walls are damaged, and valuable substances are lost Signup and view all the answers

Why is quick freezing important in food preservation?

To produce small ice crystals that do not damage cell walls Signup and view all the answers

How much faster is the rate of freezing by spraying a product with liquid nitrogen compared to liquid immersion?

25 times faster Signup and view all the answers

What is the purpose of the corrugated lower belt in the production of frozen pellets?

To give the shape to the pellets Signup and view all the answers

What is the equilibrium temperature of dry ice and vaporized CO2?

-78.5°C Signup and view all the answers

What type of equipment is often used for cryogenic N2 freezing?

Straight belt-type freezer Signup and view all the answers

What is the power requirement for a unit using liquid N2 immersion freezing?

Less than 1 kW Signup and view all the answers

What is the limitation of using liquid N2 immersion freezing for certain foods?

Freezing shock Signup and view all the answers

Study Notes

Freezing Methods

The rate of freezing by spraying a product with liquid nitrogen is 2.5 times faster than in fluidized bed freezing and 25 times faster than liquid immersion.
Frozen pellets are produced by freezing foods between two parallel moving metallic belts, with a liquid (e.g., propylene glycol/water mixture) sprayed on the external sides of both belts.

Cryogenic Liquids

Cryogenic N2 is often used in straight belt-type freezing equipment, where the product is placed on a metallic perforated belt in an insulated cabinet.
Freezing time with immersion in liquid N2 can be 15-100 seconds, and a unit requires less than 1 kW power.
Advantages of cryogenic liquid freezing include high freezing speed, low product weight loss, low initial capital, low floor space, and low maintenance cost.
Disadvantages include expensive cryogenic liquids, high consumption, dependence on few suppliers, and sophisticated storage installations.

Ice Manufacturing

Ice is formed on the internal or external frozen surface of jacketed cylinders, and knives or similar devices scrape off the ice formed on the surface.
Ice pellets can be formed by pressing "snow" or ice with relatively much nonfrozen water.
Cylinder ice or tube ice are produced by freezing water in tubes, and the belt is in a vacuum chamber at -3°C.

Cooling Equipment

Shell and Coil Equipment uses a shell and coil heat exchanger to cool water and drinks quickly.
Vacuum Cooling Equipment cools liquids in agitated jacketed vessels by applying a vacuum, reducing cooling time by 10 times.
Combined Cooling with Mixing uses recirculation, where the product comes out of the tank or silo, flows back after cooling in an efficient heat exchanger, and undergoes mixing.

Freezing of Foods

Freezing of food is a preservation method combining long shelf life with good product quality.
The quality of frozen foods depends on good initial product quality, correct application of additional processing methods, right freezing speed, hygienic processing conditions, and proper thawing.
Freezing must be done quickly to produce small ice crystals, which do not damage the cells of the products.

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Description

Learn about the benefits and drawbacks of cryogenic liquid freezing, including its effects on freezing speed, product weight, and maintenance costs. Understand the advantages and disadvantages of this freezing method.