How to Select Food Cooling Equipment by Product Type

In food processing, cooling is a critical step. Whether it is to prevent microbial growth, maintain product freshness, or prepare for subsequent packaging, choosing the right cooling equipment directly affects food quality and shelf life. This article systematically introduces common types of cooling equipment used in food processing, helping you make informed choices based on product characteristics and process requirements.

I. Basic Classification of Cooling Equipment

Cooling equipment in food processing can be classified into four major categories based on the cooling medium and working principle: air cooling equipment, water cooling equipment, vacuum cooling equipment, and contact/radiant cooling equipment. Different types of equipment are suitable for different foods, each with its unique advantages and scope of application.

II. Air Cooling Equipment

Air cooling is the most widely used cooling method, utilising flowing cold air to remove heat from food.

1. Forced-air Cooling Units

Forced-air cooling uses forced convection to lower the food temperature. Cold air blows across the food surface at a certain velocity, absorbs heat, and is then discharged.
Technical parameters: cooling air velocity 1.5–5.0 m/s (precooling can reach 3–10 m/s), applicable temperature -5°C to 15°C, relative humidity adjusted according to product characteristics.

Natural circulation cooler: uses bare-pipe coils, natural air convection, no electricity consumption, stable temperature; forced-circulation cooler: uses fan-assisted finned coolers, rapid cooling rate, suitable for fresh food storage.

2. Cooling Conveyors

After leaving the oven, bakery products enter a cooling conveyor, where they naturally dissipate heat as they are transported and gradually reach room temperature. They can be designed as straight, curved, or inclined types to accommodate plant layout. The key role is to control cooling rate and moisture release, preventing product “cracking”.

III. Water Cooling Equipment

Water cooling uses low-temperature water (typically around 0°C) in contact with food for heat exchange.

• Immersion cooling: food is directly immersed in cold water for cooling, with agitators to maintain uniform temperature and rapid cooling, but the surface may absorb water.
• Spray/overhead cooling: nozzles above the conveyor belt spray cold water evenly onto the food, suitable for large-scale production lines.
• Surface cooler (cooling plate): single- or double-stage structure; milk flows by gravity over the outer surface of the tubes to be cooled; suitable for liquid foods.
• Plate cooler: composed of several corrugated steel plates; milk and coolant flow in opposite directions, achieving high heat-exchange efficiency; used in pipeline milking systems.
• Tube-in-tube cooler: inner and outer tubes, milk flows in the inner tube while coolant flows in the annular gap.
• Immersion cooler: evaporator directly inserted into the milk storage tank, milk circulates for cooling, suitable for small and medium-sized dairy farms.

IV. Vacuum Cooling Equipment

Working principle: Fruits and vegetables are placed in a vacuum cooling chamber, and the chamber is evacuated to 666.6 Pa (approx. 5 mmHg). The moisture contained in the products rapidly vaporises at 1°C, absorbing latent heat of vaporisation (2257 kJ/kg), reducing the temperature from ambient to 1°C in just 20–30 minutes, with only 2%–4% moisture loss.
Applicable products: leafy vegetables, fresh-cut fruits and vegetables, mushrooms, and other products with high surface moisture content.
Advantages: extremely fast, uniform cooling, extended shelf life; Disadvantages: relatively high equipment cost, complex operation, uneconomical for small batches.

Core advantages of vacuum cooling: leafy greens can be cooled from 30°C to 1°C in just 25 minutes, reducing cooling time by more than 80% compared to forced-air cooling, greatly preserving chlorophyll and vitamins, and extending shelf life by 3–5 days.

V. Crushed Ice Cooling Equipment

Crushed ice cooling uses the heat absorbed during ice melting (335 kJ/kg) to cool food. Ice is portable, harmless, inexpensive, and usable at room temperature. Types of ice include tube ice, granular ice, and large-block crushed ice. Typical applications: spreading crushed ice over food in cold storage rooms at 0–3°C for cooling, or placing ice among ambient-temperature goods for simple pre-cooling, especially suitable for aquatic products and some fruits and vegetables during transport preservation.

VI. Contact/Radiant Cooling Equipment

1. Contact Cooling

Food comes into direct contact with a cooled surface for heat exchange, including single-contact and double-contact freezers, suitable for block-shaped foods, meat, and fish fillets.

2. Radiant Cooling

Utilises low-temperature radiating surfaces to absorb infrared radiation emitted by food; heat transfer is relatively slow but uniform, suitable for special process requirements.

3. Hybrid Cooler (with air-blast shelf)

The product to be cooled directly contacts the evaporator coils, involving conduction, convection, and radiant heat transfer, resulting in rapid cooling and suitability for freezing pan-packed products (fish, shrimp, offal, cut meat).

VII. Direct Cooling vs. Indirect Cooling Systems

Direct cooling: The refrigerant evaporator is placed directly inside the cooling unit, providing fast cooling and a low temperature difference; widely used.
Indirect cooling: The refrigerant first cools a secondary coolant (brine, ethylene glycol), which then cools the air or food, maintaining a stable temperature suitable for applications requiring constant temperature (e.g., brine ice-making). In milk cooling equipment, direct-expansion bulk tanks cool milk with refrigerant; indirect-expansion bulk tanks use a secondary coolant and are equipped with a thermal storage tank.

VIII. Applicability Comparison of Various Cooling Equipment Types

(This section corresponds to the original, presented as a descriptive summary based on the original text’s intention. According to the original layout, it is a comparative section.)

Air cooling equipment is suitable for baked goods, fruits, and some meat products with moderate cooling time requirements; water cooling provides fast cooling for liquid foods, poultry, and some vegetables but may cause surface moisture; vacuum cooling is best for leafy greens and high-surface-area products with extremely high cooling speed; contact/radiant cooling is excellent for solid, flat or packaged food requiring uniform temperature reduction; crushed ice cooling is ideal for aquatic products and transport scenarios where low-cost, portable cooling is needed. Each category has distinct performance in capacity, energy consumption, and product integrity.

IX. Selection Guidelines

• Product characteristics: Leafy vegetables are cooled by vacuum; liquid products prefer plate or tube-in-tube coolers; baked goods often use spiral towers or racetrack coolers.
• Production scale: Large-scale continuous production favours tunnel-type or spiral cooling equipment; small batches may choose cold rooms or immersion cooling.
• Space limitations: When floor space is limited, spiral cooling towers or cascade-type coolers can significantly save footprint.
• Hygiene requirements: Equipment that directly contacts food must comply with food-grade standards (e.g., stainless steel mesh design).
• Energy consumption considerations: Racetrack coolers have relatively low energy consumption; natural circulation coolers consume no electricity.

Practical case: After introducing a spiral cooling tower + layered temperature control system, a large bakery improved cooling uniformity by 35%, reduced product cracking rate from 2.1% to 0.4%, while saving 45% of plant floor space. Vacuum cooling applied to a fresh-cut lettuce production line shortened pre-cooling time from 2 hours to 25 minutes, extending shelf life to 12 days.

X. Conclusion

There are many types of cooling equipment in food processing, ranging from traditional air cooling and water cooling to highly efficient vacuum cooling and spiral cooling towers. Each type of equipment has unique application scenarios. Choosing the right cooling equipment not only affects product quality retention but also directly impacts production efficiency, energy costs, and floor space utilisation. With the continuous development of food processing technology, cooling equipment is evolving toward high efficiency, energy saving, automation, and intelligence. The integration of novel cooling technologies with traditional processes will provide more optimisation options for the food industry. When selecting equipment, manufacturers should fully consider product characteristics, production scale, and process requirements to choose the most suitable cooling solution for their needs.

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This article is intended as a reference for food plant process design, equipment selection, and quality control, covering the four major cooling technology systems: air/water/vacuum/contact cooling.