Don't Put Tomatoes in the Fridge

Science now tells us that refrigeration ruins tomatoes' glorious taste.

I remember when my old college roommate expressed horror at seeing me put a pint of cherry tomatoes in the fridge. “Never do that! They lose all their nutrients,” she said to me, shocked. Ever since, I’ve left tomatoes out of the fridge, without really understanding why. Now science has proven her mostly right. It is not nutrients so much as flavor that gets lost.

A new study published last week in the Proceedings of the National Academy of Sciences has found that refrigerating tomatoes does indeed ruin their flavor.

“Chilling fruits at temperatures below 12 degrees Celsius hampers enzymes that help synthesize flavor-imparting volatile compounds, resulting in relatively fresh but insipid fruits.”

A team of horticultural researchers, led by Bo Zhang of the University of Florida, studied 25,000 genes in a variety of tomatoes, both heirloom and conventional varieties. These tomatoes were refrigerated at 41°F for one, 3, or 7 days, and then left at room temperature for an additional day to recover. The fruits were then eaten and assessed for flavor; volunteers found that chilled tomatoes were much less tasty than non-chilled.

While one day of refrigeration didn’t make much difference, the longer periods of refrigeration did have a lasting effect, suppressing the genes responsible for making ‘volatile compounds’ that help provide flavor. These volatiles are synthesized during ripening, giving the fruit a strong smell, but they don’t stay inside the fruit. They escape through the stem scar, and a week in the fridge gives them plenty of time to do that.

The Washington Post explains:

“Using RNA sequencing, [the researchers] were able to figure out which genes were expressed differently when chilled. It turned out that affected genes numbered in the hundreds (the tomato genome has 25,000 genes — about 5,000 more than humans). Refrigeration set off a cascade of changes, starting with a set of cold signaling genes and moving through the ones responsible for metabolism, ripening and volatile synthesis. It also affected DNA methylation — the mechanism that cells use to control which genes get turned on and off.”

Refrigeration is used to extend the shelf life of tomatoes and to prevent them from rotting prematurely. So even if you don’t refrigerate your tomatoes, they likely have been chilled at some point along the line by transportation companies and supermarkets. Tomato-philes will have to start growing their own, or at least sourcing from local farmers who pick them right out of the field on the day they’re sold.