The preservation of food by freezing has become a major industry.Preservation of a food by freezing occurs by several mechanisms. At
temperatures below 0°C there is a significant reduction in growth
rates for microorganisms and in the corresponding deterioration of
the product due to microbial activity.
Several freezing systems for food operate with direct contact between
the refrigerant and the product.
cryogenic freezer is direct contact freezer.
2. What is Cryogen
• Colorless, odorless, Chemically inert substances
• Non toxic in normal concentration
• Have low boiling point
• Safe for direct contact with food
• Commonly use cryogens are liquid nitrogen, liquid or
solid carbon dioxide
3. Cryogenic Freezer
• Direct contact freezer
• Cryogen is directly contact with the food.
• The heat of food provides the latent heat of
vaporization or sublimation of the cryogen.
• Change the state in the cryogen.
• Rapidly removes heat from all surfaces of the food
to produce rapid freezing.
5. Types of Cryogenic Freezing
• SURFACE FREEZING/CHILLING -Reduces
product moisture losses when used with
mechanical blast freezing.
• CRUST FREEZING – Decreases time required to
totally freeze product
• FULL FROZEN - Used for long periods of
packaging or where product is immediately
shipped.
6. Cryogenic freezer conveyer configuration
Spiral Freezers
Flighted Freezers
Straight Belted Freezers
– Standard Co2 or LN2 Tunnels
– Impingement Tunnels
– LN2 Immersion Tunnels
Triple Pass Freezers
Rotary Drum Freezers
Cryo Mechanical Systems
7. CO2 or LN2 Spiral Freezer
• Utilizes minimum floor
space
• Retains product flavor,
texture & moisture
• Short dwell time
• Easy to operate, maintain
& clean
• Low capital investment
8. LN2 Immersion Freezer
• Instantly freezes product
• Reduces product damage
& yield loss
• Boosts production
• Ideal for difficult to
handle, wet, IQF, and high-
value product
• Ideal for pre-chill
9. Flighted Freezer
• Continuous serpentine belt
• Ideal for IQF products
• Adjustable belt speed and cryogen
injection
• High freezing rate
• CO2 Belt snowing is available to
reduce product sticking
10. Application
• High Value yield sensitive products
–Steam cooked diced chicken
• Difficult to handle products
–Pizza
–Marinated Chicken
–IQF Shrimp
–Cooked Pasta
• Boosting Mechanical Systems
11. Advantages
• Low cost capital investment
• Modular, space saving designs
• Adjustable to different products
• Fast, efficient heat transfer
• Accommodates varied production schedules
• Saves time and reduces labor costs
• Better quality product
