University of California

Ask the Produce Docs (General)

We only have one forced air cooler, can I cool both my tomatoes and watermelons together?

Category
  • Ethylene
Question

Can I ask a couple of questions about watermelon storage?

1) We greatly increased our mini-seedless watermelon program this year.   However, we also have a big vine-ripe heirloom tomato program.  And we only have one forced air cooler. The melons will be forced air cooled in the same warehouse where the tomatoes are stored.  They will not be stored there but will potentially be exposed to ethylene as they are force air cooled and stored on location for up to 6 hours.  

Will this cause significant impact to the shelf life of the melon?

2) Ethylene scrubber.  If we installed an ethylene scrubber in the room where the tomatoes are stored will this significantly improve the shelf life of the tomatoes/ or significantly reduce collateral damage to watermelons?  Is there a type of scrubber you prefer, and do you have any tips for installation? (N.B.)

Answer

Watermelons, at least the traditional varieties, are not very susceptible to ethylene damage.  Our webpage “Produce Facts: Recommendations for Maintaining Postharvest Quality of Watermelon” indicates:  

"Exposure to ethylene concentrations as low as 5ppm for 7 days at 18°C (64°F) will cause unacceptable loss of firmness and eating quality.”

5ppm is a relatively high concentration of ethylene for most storages and you likely do not exceed this level, although it would be useful to measure the ethylene levels in the storage room. You can test your system by setting aside a sample of the melons for several days to see if they develop a mushy texture.

Generally speaking, ventilation with outside air is the least expensive way to reduce ethylene levels.  The easiest way to accomplish this is to install an exhaust fan with a capacity of one to two air exchanges per hour.  The cost of the electricity to refrigerate the incoming air will usually be less than the capital and operating costs of other ethylene control methods.

I hope this helps.

-Jim Thompson

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