What Is Vacuum Cooling?

Vacuum cooling is a rapid cooling method based on pressure reduction. When air pressure is lowered inside a sealed chamber, water inside the product begins to evaporate at low temperatures.

This evaporation removes heat from the product, enabling extremely fast cooling compared to conventional methods.

The process is driven by:

• Evaporative Cooling
• Heat Transfer

Result:
Fresh produce can be cooled from field temperature to 2–4°C in 15–25 minutes, instead of several hours.

Why Vacuum Cooling Extends Shelf Life

The key advantage lies in how fast temperature drops after harvest.

1. Reduced Respiration Rate

Fresh produce continues to respire after harvesting. Rapid cooling slows metabolic activity, delaying aging and quality loss.

2. Lower Moisture Loss

Fast cooling reduces transpiration, helping maintain:

• Leaf crispness
• Visual freshness
• Weight stability

3. Reduced Microbial Growth

Quickly passing through the critical temperature zone (10–60°C) minimizes microbial activity, improving food safety and shelf stability.

4. Less Condensation Risk

Unlike slow cooling, vacuum cooling avoids surface condensation—reducing fungal growth and spoilage.

Case Study: Hydroponic Grower Pura Hoja

This is according to Tomás Benavente with Pura Hoja, the biggest producer of hydroponic lettuce in Chile. Because of the thin and narrow shape of the country, distribution is a major complication for hydroponic products. Cooling their produce helps them to keep the lettuce as fresh as possible before it reaches the grocery shelves.

Hydroponic lettuce & Vacuum Cooling

Pura Hoja was established in 2010. Over the last decade, the company grew out to be the biggest producer of hydroponic lettuce in Chile. On their NFT-system, they currently grow lettuce, while carrying out trials with herbs and baby greens. According to Tomás the company is technologically capable of producing any green leaf vegetable on their facility. He believes there’s a big opportunity for the agricultural industry to grow more efficient by using technology, yet the market has to appreciate these products as well.

“Producing a healthy crop year-round is a big challenge. Technologies controlling climate, disinfection and sanitization, the fertilization, and crop management are extremely important. With these techniques, we can control all the environmental climate conditions,” Tomás says.

“The moment of harvest has to be planned carefully, as the lettuce shouldn’t be too old. Then the temperature control is of crucial importance. The complete post-harvest chain ideally takes place in a room with a temperature between 2-5 °C, depending on the crop.”

For additional shelf life, Pura Hoja has been working with a vacuum cooler for the past two years. This cooler, provided by the Dutch company WeberCooling (Weber Vacuum Group), helps them to keep the lettuce as fresh as possible before it reaches the grocery shelves.

“By reducing the pressure inside the vacuum room, you force (a fraction of) the product’s own moisture to evaporate,” says Sylvia van Uden with Weber Cooling. “This evaporation costs energy, which is taken from the produce in the form of a temperature reduction.”

The team with WeberCooling is also very active with their technology in the US market for vertical farming and in Latin American. Both hydroponic growers as vertical farmers have chosen it for the systems, as it extends the shelf life of the produce. The same goes for Pura Hoja.

“The vacuum cooler helps us to drop down the temperature very quickly after the harvest, which affects the shelf like of the product directly,” says Tomás. “After harvesting the products, we cool it for at least 20 minutes. This process enables us to prolong the shelf life by 2-6 days minimum, and according to some figures even to 10 days. This way, we deliver healthy lettuce with a maximum freshness to our consumers.”

Applications in Hydroponic and Indoor Farming

Vacuum cooling is particularly effective for:

• Lettuce (butterhead, iceberg, romaine)
• Fresh herbs (basil, coriander, parsley)
• Baby leaves and mixed salads
• Vertical farming crops

These products benefit from:

• High surface-to-volume ratio
• High water content
• Rapid heat removal efficiency