"Never refrigerate your tomatoes!"
You hear it every single year, starting in summer and repeated into fall, as gardens across the country give up the last of their fresh tomatoes. The problem is, it's not good advice—when it comes to tomato storage, best practices are significantly more nuanced.
The most recent wave of articles on the subject was triggered by a newly published research paper on how cold storage interrupts the production of volatile aromatics in picked tomatoes. That's right. We've got science on our side now! say reporters, and they say it again and again and again.
The thing is, science doesn't have an agenda, so the results of studies are only as useful as the manner in which they are interpreted and applied. And in the case of tomatoes and refrigeration, we misapply scientific research all the time.
So today, I'm going to try to set the record straight and explain exactly when it's a bad idea to refrigerate your tomatoes, and when it's A-OK. First, let's give you the useful part; then we can get into the explanation.
If your tomatoes have never been refrigerated (i.e., if you grew them yourself or bought them from a farmers market stand you trust, in-season):
- Remove their stems and store unripe tomatoes upside down on a plate or cutting board at room temperature until they ripen.
- Consume fully-ripened tomatoes immediately.
- Refrigerate any unconsumed fully ripe tomatoes for up to three days, allowing them to come to room temperature before serving them (to speed up this process, slice them while still cold—slices will warm up much more quickly than an intact fruit).
If your tomatoes have been refrigerated (i.e., you got them anywhere other than your backyard or the farmers market, in-season):
- Leave them at room temperature until fully ripe, then store in the refrigerator until ready to use.
It's as simple as that. Now here's the explanation.
What the Science Really Says
If, like me, you are inclined to support science and pay the $10 fee to read this new study, you can do so here. Otherwise, you'll just have to take my interpretation at face value.
Most of the study is about the mechanism by which the production of various volatiles is delayed or halted during refrigeration. It's all really interesting, but the passage that people seem to be glomming onto comes from the second page:
"To determine whether the reduction in volatile contents following cold storage affected flavor quality, a consumer panel was conducted. Fruits chilled for 7 d followed by a 1-d recovery at 20°C were compared with fruits harvested at the same stage of ripeness on the day before the consumer panel. Chilled fruits were rated significantly lower for overall liking (P < 0.03), indicating that the chilling treatment negatively affected flavor."
That last sentence—"chilling treatment negatively affected flavor"—is the one that people are using to support the idea that refrigeration ruins tomato flavor. Unfortunately, like Arthur Dent, we got an answer from science, but we lost sight of what the question was in the first place.
That question—the one most home cooks want answered—is: How should I store my tomatoes?
Meanwhile, the passage from the study was tackling an entirely different question. Namely, If I store a tomato in the fridge for a week and then leave it on the counter for a day, will it taste better or worse than a tomato I picked straight from the vine yesterday?
The two questions are not the same. As someone on Twitter said to me, using this as evidence that we should never refrigerate tomatoes is like saying, "These scallops that sat in the fridge for a week are worse than the ones I caught fresh today, therefore scallops should never be placed in the refrigerator." Do you see the ridiculousness of the conclusion now?
Most experimental science, by design, takes a very reductionist view. The questions a given experiment tries to answer are small in scope, and variables are limited so that we can get concrete answers. These concrete answers become the building blocks for more and more complex theories, but each step in science is a small one. That's the danger of taking the results of a single study and using it to make blanket statements for a broad range of situations.
I wrote an email to Dr. Harry John Klee, the author of the study, inquiring about this passage and the conclusions drawn from it. Here's what he had to say:
"First and foremost, it would be impossible to pick tomatoes on a single day, refrigerate half for seven days and leave the other half at room temperature for seven days. The ones left at RT would be far riper and in fact likely be well past their optimum. It would not be a fair comparison."
He goes on to explain how the tomatoes are grown in greenhouses with consistent water and fertilizer regimens and thus have a high level of consistency from batch to batch, and that the chemical content of the flavors are similar between harvested batches.
"The bottom line is that there is no better way that we can come up with to compare the effects of chilling. It's not perfect but it's pretty darned close."
This is a very reasonable way to approach an experiment, and, as Dr. Klee points out, comparing tomatoes stored at room temperature for a week versus those stored in the fridge for a week would not be a useful or fair comparison, and would not go far in helping answer the question of what happens while tomatoes are refrigerated.
But as home cooks, our goals are different from his. All we care about is the best thing to do with our tomatoes once we get them home.
The Best Way to Store Tomatoes
In an ideal world, we'd all have tomato vines in our backyards,* harvesting peak-of-ripeness tomatoes and eating them soon after harvest.
*Bay Area brag: I live in the ideal world by that standard.
But in the real world, the vast majority of us buy our tomatoes from a variety of sources. More often than not, we also buy or harvest them in batches. We eat what we can, but we wind up with more than we can consume. At this point, we're faced with a conundrum—where do I put the rest of these?
The refrigerator will definitely extend a tomato's overall life—the amount of time before it starts to actually rot—but there are undeniable downsides to extended cold storage. This new study shows volatile loss after a week. Some older studies give an even shorter timeframe. Texture-wise, there are also drawbacks, and many studies show that texture degrades with extended chilling.
But the issue is that most of these studies are aimed at commercial scenarios, in which tomatoes are stored for extended periods of time (from a couple of weeks all the way up to a month). What they don't do—please correct me if you've seen examples to the contrary—is compare the disadvantages of short- to mid-term refrigeration to the disadvantages of leaving a tomato out at room temperature for the same time periods.
The very reason why we refrigerate tomatoes is to extend their shelf life. Even according to Dr. Klee, if we didn't, they'd "likely be well past their optimum." So then the real question becomes: is the bad stuff that happens when you do refrigerate a tomato worse than the bad stuff that happens when you don't?
We decided to run our own set of experiments, designed to answer the questions that home cooks are actually interested in. We repeated the testing throughout the entire summer of 2014, in July, early September, and again in late September, each time refining our findings until we were satisfied with the results.
Let's set up four potential scenarios for home cooks:
Scenario 1: You have ripe tomatoes from the farmers market or your garden that you will eat over the course of a few days
In this situation, we found that the negative effect from deterioration that occurs to tomatoes that are left on the countertop is greater than the negative effect of deterioration due to cold storage. We also found that when it comes to short-term storage, refrigerated tomatoes can recover from any damage by being allowed to warm back up before serving. This should not actually be that surprising. In fact, according to the very same paper we quoted at the start, refrigerating tomatoes for periods of one to three days produces no ill effects as far as flavor goes:
"Red ripe fruits were stored at 5 °C for 1, 3, or 7 d followed by a recovery period of either 1 or 3 d at 20 °C, and volatiles were measured. Compared with the day of harvest (day 0), no significant loss of flavor volatile content was observed after 1 or 3 d of cold storage."
It is quite specifically stating that you can refrigerate your tomatoes for up to three days, no problem!
In this scenario, refrigeration wins.*
*The one caveat is for those people who are so impatient that they do not want to wait for a chilled tomato to warm back up. If you simply must be able to eat a warm tomato at moment's notice, then the equilibrium probably sways back in favor of countertop storage for you.
Scenario 2: You have ripe tomatoes from the farmers market or your garden that you'll eat over the course of a couple weeks
For longer term storage, the answer should be even more obvious. If a ripe tomato over-ripens within a few days at room temp, you can bet your butt it's gonna be way over-ripened if left for longer. Refrigeration wins again.
Scenario 3: You have slightly underripe tomatoes from the farmers market or your garden that you want to eat over the course of a few days
In this case—which may be a frequent case for those buying tomatoes from the farmers market—room-temperature storage wins. Because volatile production is inhibited at lower temperatures, a refrigerated tomato will not properly ripen and develop flavor. With long enough storage, its ability to do so may even be permanently lost.
Store underripe tomatoes on the counter until they are fully ripe, then eat them or refrigerate them. It's worth noting that most moisture and volatiles are lost through the scar on the stem-end of the tomato. You can combat this loss by either storing the tomatoes upside down or placing a small piece of clear tape over each stem-end.
Scenario 4: You have any tomato from the supermarket
Virtually any tomato you buy from the supermarket—the vast, vast majority of fresh tomatoes Americans purchase—has already been refrigerated during transport and ripened under refrigeration. This means that it is already at a permanent disadvantage when it comes to both flavor and texture. You may be able to eke out a tiny bit more flavor by letting severely underripe specimens sit on the counter or salting and draining them before use, but in all likelihood, additional refrigeration is not going to hurt them and will only serve to extend their shelf life. Fridge wins again.
So the next time you hear someone tell you that science says you should never refrigerate your tomatoes, turn up your nose and say, "Well, correctly applied science says that I should."
Then offer them a tomato and ask them to forgive you for being such a snob.