Precool First, Package Second: A 5-Ton Cherry Line

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Modified atmosphere packaging (MAP) only works when the product inside the package is already thoroughly chilled. That sounds simple, yet it is the step most packing houses skip most easily. This article covers a real 5,000 kg cherry line and where the fruit and vegetable vacuum pre-cooler sits in the overall process.

Loading Hot Cherries into MAP Bags Brings Problems

Cherries picked in the morning have a fruit temperature of 25–30°C. At this temperature the respiration rate is roughly 5–8 times that at 2°C. A MAP bag is a closed system; the film controls the ingress and egress of oxygen and carbon dioxide, but respiration keeps consuming oxygen, and the film cannot stop that.

When hot cherries are loaded into MAP bags, the gas inside the bag changes quickly: oxygen drops, carbon dioxide rises, and the fruit begins anaerobic fermentation — flavor deteriorates, flesh softens, and stems turn brown. Film cannot solve this problem, because the root cause is heat, not gas. MAP is therefore a maintenance technology, not a cooling technology.

Real Project: 5-Ton Cherry Vacuum Pre-cooler (with Water Spray Function)

Our most recent cherry line uses the CVF-5000 with water spray function. Parameters are as follows:

Cherries enter the chamber at 25–30°C. In a 30–45 minute cycle, the chamber is pumped down to ≤600 Pa, moisture evaporates from the fruit surface, and heat is discharged along with the water vapor. The vapor condenser is maintained by the refrigeration system at −5°C to −15°C, condensing the water vapor back into liquid. Without the refrigeration system there is no condensation; the vacuum pump working alone would emulsify its oil and the system would fail within minutes. The refrigeration system on this machine is not an option — it is the core of the entire process.

The water spray function coats the fruit surface with a thin film of water during cooling to control weight loss. Cherries are sold by weight; on a 5,000 kg batch, a 2–3% difference in weight loss is real money, and exporters are very sensitive to this.

Why the Pre-cooling Sequence Determines MAP Performance

When the CVF-5000 discharges, the cherries have already been cooled to 0–10°C, go directly to the grading line, and are then packed into MAP bags. The typical gas mix for cherry MAP bags is 5–10% oxygen and 10–15% carbon dioxide, stored at 0°C. Chilled fruit at 2°C respires slowly, and the gas inside the bag can remain stable for weeks. This is the difference between cherries that arrive firm after a 3–4 week sea voyage and those that arrive already soft.

Cold room cooling takes 12–24 hours to bring the fruit core down to the same temperature. During that time respiration keeps running at the high-temperature rate and moisture is continuously lost. Vacuum pre-cooling completes the same cooling task in 30–45 minutes; by the time the MAP bag is sealed, the fruit inside is already in a low-metabolism state.

A Workable Process Sequence

1. Harvesting, rough sorting and removal of debris
2. CVF-5000 vacuum pre-cooling: 25–30°C → 0–10°C, 30–45 minutes
3. Grading, weighing, loading into MAP bags
4. Temporary storage in a 0–2°C cold room until container loading

One detail worth repeating: the pre-cooler goes upstream of the packaging line, not downstream. Product entering the packaging machine is at ≤10°C. The cold room is only a transfer buffer, not the primary cooling equipment.

The logic is the same for smaller lines. The CVF-2000-4P (2,000 kg/batch, 19.3 m³, 112 kW cooling capacity, 15–30 minute cycle) covers mid-sized packing houses; the process is unchanged, only the scale differs.

MAP Without Pre-cooling: What Actually Happens

The most common mistake: package first, cool later. Hot cherries deplete the oxygen inside a MAP bag within a few hours. Some films have high oxygen transmission rates and try to compensate, but then the gas mix drifts toward ambient concentration and MAP loses its purpose. The result is paying for film without getting the film's benefit.

Another mistake: cold room first, MAP later. The product does eventually get cold, but the 12–24 hour delay costs moisture, firmness, and shelf life — exactly what the exporter is selling.

Conclusion

Vacuum pre-cooling and MAP do two different things. One removes field heat in 30–45 minutes; the other keeps a cold product in a stable gas environment. Used together in the right order, cherries can hold their shelf life through a 3–4 week export voyage. Used alone, both are compromised.

CVF Seriescovers fruit and vegetable lines from 1,000–6,000 kg/batch. If you are building a MAP line, the first engineering question is not what film to buy, but where in the process the cooling equipment goes.

Reference sources: Yuanxian Machinery project files, CVF-5000 cherry line (5,000 kg/batch, 2026), CVF-2000-4P Dujiangyan, Sichuan configuration. Published 2026-08-07.

Related reading:

• Solutions: Fruit and Vegetable Cold Chain
• Knowledge Base: Vacuum Cooling Fundamentals
• Products: Fruit and Vegetable Vacuum Pre-cooler Models