If you’ve been reading my blog for a while, you know I love to cook. After all, I’m a frustrated chem e who no longer has a full-time lab at his disposal. The kitchen serves as my surrogate facility.

And, on any given day, my dinner plans include a salad. Sometimes, it’s the whole meal (by adding a cut steak, tuna medallions, chopped egg or cheese- anything with protein. Of course, I also prepare my own salad dressing from scratch.

For years, I’ve been keeping my tomatoes next to my herb garden. Which sits on my kitchen counter, so that these round beauties can be afforded the use of the special illumination that I use for the garden.

I’ve never kept my tomatoes in the fridge. (It had been a bone of contention with my spouse, who always wanted them in the “vegetable bin’.) And, now, there’s scientific data to substantiate my practise.

Drs. Bo Zhang, Denise M. Tieman, and Harry J. Klee (senior author) of the University of Florida; Chen Jiao, Yimin Xu, Zhangjun Fe, and James J. Giovannoni, all from Cornell, and Kunsong Chen of Zhejiang University (China) published their paper, Chilling-induced tomato flavor loss is associated with altered volatile synthesis and transient changes in DNA methylation, in the Proceedings of the National Academy of Sciences.

It turns out that while cold storage may be great for keeping apples, pears, and other fruit at their peak, that does not hold for tomatoes. (Yes, Virginia, tomatoes are scientifically termed fruits, not vegetables.) Moreover, chilling fruits at temperatures below 12 C (53.5 F) impairs the ability of the fruit to synthesize flavor-imparting compounds.

Fruits derive their flavor from their components- sugar, acidity, and volatile organics (which often yield the aromatic smells we enjoy). The researchers believe it is the volatile organics changes that render commercial tomatoes so lacking in flavor. It’s not how they are grown, but what happens post-harvesting. Chilling them may preclude tomatoes from rotting, but what you are left with is a tasteless orb. (Sugars and acids are not greatly affected by refrigeration, but the volatile organics are either formed or augmented as the fruits ripen.)

The researchers tested tomatoes stored at 5 C (41 F), after 1, 3, and 7 days. They also allowed the tomatoes to recover for 1 to 3 days at room temprature. (This recovery concept was included because we know some genes critical to volatile formation recover after a return to a 20 C environment.) But, sometime between 3 and 7 days, the tomatoes lost their volatiles- and the recovery period was unable to perform magic; unable to restore the volatile organic levels.

The tomatoes also underwent taste testing, using 76 volunteers. All those tomatoes that were chilled and not stored at room temperature significantly failed the taste test. It seems the volatiles (not the sugars nor the acids) escape through the spot where the fruits were initially attached to the plant (called a stem scar)- so even if the picked tomato were superb and bursting with flavor, those 7 days of chilled storage provide for the escape of the volatiles.

Scientifically, hundreds of the 25000 genes in a tomato (that’s 5000 more than we humans contain) underwent a variety of changes when stored in a fridge. These included those responsible for metabolism, ripening, and the production of volatiles. It seems that DNA methylation- the process by which genes are activated or made dormant- was the characteristic most clearly affected.

(Maybe now it’s a good time to explain why cold storage works for apples, pears, and similar fruits.  You see, while the temperatures are close to 4 C, the storage is vastly different than in your fridge or grocery stores.  As I’ve written, these storage facilities are sealed, providing storage conditions with relative humidities of 90%, and in carbon dioxide rich [and oxygen deprived] atmospheres.   This clearly retards- and probably suspends- the formation of volatiles, so the fruits stay ready for our best, first bites.)

So, if you like your fruits (especially tomatoes) tasty- keep them out of the fridge. Yes, it means you have to buy them more often (and maybe even find a way to grow them yourself- indoors).

Trust me, your dinner salads will be truly satiating.

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