Why are leafy vegetables cooled immediately after harvest?

In vegetable farming, leafy vegetables are cooled immediately after harvest—a process known as precooling—to remove field heat and maintain product quality. This rapid removal of heat is essential for several reasons:12

• Slowing Deterioration: Cooling slows the natural biological deterioration that begins immediately after harvest, helping the produce reach the consumer at maximum quality.1
• Inhibiting Decay: It slows the growth of decay-causing organisms.1
• Reducing Water Loss: By retarding water loss, precooling helps prevent the vegetables from wilting.1
• Extending Shelf Life: Low-temperature storage is critical for maintaining the quality of leafy greens, as it helps prevent senescence and preserves freshness.2

Common methods for cooling these crops include vacuum cooling, which is particularly well-suited for lettuce, cabbage, and spinach, as well as hydrocooling, contact icing, and air cooling. Maintaining these low temperatures throughout shipping and storage is vital to prevent significant postharvest losses.12