THE TOMATO RACING AGAINST THE CLOCK

A tomato is still alive after being harvested. It breathes, loses water, produces ethylene and continues to ripen during transport. That's why preserving it is not simply about keeping it as cold as possible.

Tomatoes present a minor logistical challenge: we want to slow down their ripening without halting the process in a way that compromises quality.

UC Davis places the optimal storage temperature for a "breaker" (turning) tomato between 12.5 and 15°C. At 12.5°C, it can be stored for up to 14 days before ripening begins, without a significant loss in sensory quality or color development.

But there is an even more interesting fact: cooling them further does not necessarily mean preserving them better.

A tomato can deteriorate both from excess heat and from excess cold.

A tomato can also get too cold

Tomatoes are susceptible to what is known as "chilling injury." UC Davis warns that keeping tomatoes below their optimal temperature range for too long can lead to ripening issues, loss of flavor, color changes, and increased susceptibility to deterioration.

"Breaker" or mature-green tomatoes can suffer this type of damage at temperatures below 10°C if exposed for extended periods; at 5°C, the problem can manifest after just 6–8 days.

It is an interesting paradox. For many fresh products, lowering the temperature helps extend shelf life. With tomatoes, however, there is a threshold beyond which the cold itself becomes part of the problem. That is why the tomato cold chain is, in reality, a temperature-controlled chain.

Even after being harvested, the tomato remains alive: it breathes, consumes oxygen, and continues to ripen during the journey.

Even though it's in a box, it's still breathing.

After being detached from the plant, the tomato remains living tissue. It consumes oxygen, releases carbon dioxide, and maintains metabolic activity—activity that varies significantly with temperature.

According to data from UC Davis, a "breaker-stage" (turning) tomato exhibits a respiration rate of approximately 6–9 ml of CO₂/kg·h at 10°C, compared to 14–21 ml at 20°C. In other words, as the temperature rises, metabolism accelerates—and with it, the biological clock.

That is why temperature control begins very early on. UC Davis recommends rapid cooling after harvest, citing 12.5°C as the standard target temperature for pre-cooling. Forced-air cooling is one of the most effective techniques for achieving this uniformly.

The gas that can trigger ripening

The tomato also belongs to the group of climacteric fruits. This means that its ripening is closely linked to ethylene, a gaseous plant hormone.

A mature-green tomato exposed to ethylene begins to ripen. In fact, commercial facilities can use it in a controlled manner to synchronize this process before the product goes on sale. UC Davis cites standard ripening conditions as 18–21°C, 90–95% relative humidity, and approximately 100 ppm of ethylene.

The tomato itself also produces ethylene. At 10°C, it produces approximately 1.2–1.5 µl/kg·h; at 20°C, production rises to 4.3–4.9 µl/kg·h. This introduces another variable in transport: which products travel together.

UC Davis advises against storing ripening tomatoes alongside ethylene-sensitive products such as lettuce or cucumbers, because the released gas can affect the quality of those goods.

Humidity also has a window.

Temperature gets most of the attention, but there is another important figure: 90–95% relative humidity. That is the range recommended by UC Davis to limit water loss and maintain postharvest tomato quality. Humidity that is too low promotes dehydration.

However, keeping it too high does not solve the problem either: excessive humidity over prolonged periods or the formation of condensation can encourage mold growth on the surface and around the stem scar. Once again, managing a perishable product is a matter of staying within a specific window.

In the logistics of perishables, even the air surrounding the product is part of the journey.

Humidity and atmosphere: air preserves, too.

Temperature is not the only variable that matters. UC Davis recommends maintaining tomatoes at a relative humidity of around 90–95% to reduce water loss and preserve quality. However, there is a limit here too: excessive humidity or the formation of condensation can promote mold growth.

For longer journeys or storage periods, the air composition can even be modified. Atmospheres containing approximately 3% oxygen and between 0% and 3% CO₂ can delay ripening and extend the shelf life before the tomato begins to ripen.

The balance is delicate: too much CO₂ or too little oxygen can cause damage, unpleasant odors, or internal defects. Therefore, for perishable products, preservation means more than just cooling; it also involves controlling humidity, oxygen, and carbon dioxide levels.

The journey of a grain of rice

Invisible stories of global transport.

A series by Transped exploring the routes, technologies, infrastructure and decisions that keep goods moving.