How do you keep ripe tomatoes from going bad?
Some people say that you should never refrigerate tomatoes. Is this accurate?
So many people have warned me not to refrigerate my tomatoes for so long that I’m not sure I’ve ever done anything other than leave them on my counter. But the question has made me think back on it, and to be honest, I can remember losing quite a few beautiful summer tomatoes over the years to rapid rot and decomposition, because they were sitting out in sweltering heat.
And I believe this goes to the heart of the problem with this rule: While refrigerators tend to operate within a narrow band of temperatures, usually in the 35-to-40°F (2-to-4°C) zone, the actual temperature of most rooms can range anywhere from about 60°F (16°C) to upwards of 100°F (38°C), particularly if it’s an un-air-conditioned space at the height of summer. For example, I’m typing this while sitting in my hot apartment, and I’m guessing it’s at least 90° in here based on the quantity of perspiration dripping from my lower back into my chair. Is it true that 90°F is better for tomatoes than 37°F? And, if so, how long?
To answer these questions, I set up a series of experiments that spanned an entire summer and included literally hundreds upon hundreds of tomatoes of different sources, varieties, and quality and ripeness levels, and recruited a small army of blind-tasters to evaluate the results. I even requested Kenji to repeat the experiments in California to ensure if my findings were repeatable.
Before I go into the specifics of my testing, let me first explain my findings and provide some suggestions. They’re controversial only because they buck what has become conventional and deep-rooted wisdom; but really, what I found makes a lot of sense.
Should You Refrigerate Tomatoes? Here’s the Short Answer
If your tomatoes have never been refrigerated (i.e., whether you cultivated them yourself or purchased them in season from a reputable farmers market stand):
- Remove the stems and store unripe tomatoes at room temperature, upside down on a plate or chopping board. (Why is it upside down? Read Kenji’s post to see why it’s preferable to plant stem side down.)
- Consume fully ripened tomatoes immediately.
- Refrigerate any completely ripe tomatoes that have not been eaten, but allow them to come to room temperature before serving. (To speed up this process, slice them while still cold—slices will warm up much more quickly than an intact fruit.) According to one research, refrigerating for no more than three days is ideal.
If your tomatoes have been refrigerated (That is, assuming you acquired them anywhere other than your backyard or a farmers market during the season):
- Let them to ripen at room temperature before storing them in the refrigerator until ready to use.
*If you want to read the whole research, you may do so here. But this is the relevant quote: “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. There was no significant loss of taste volatile content after 1 or 3 days of cold storage when compared to the day of harvest (day 0).”
That’s all there is to it. Now, here’s the (brief, for now) explanation.
A refrigerator is cold—colder than tomatoes like. This is a basic fact, and it’s the fact upon which the “never refrigerate a tomato” rule is based. Yet, that rule ignores certain real-world variables that might complicate matters. It also fails to recognize that not all tomatoes are affected by refrigeration equally.
So here’s what you should know: Keep your tomatoes at room temperature for as long as possible, particularly if they’re still a touch green. As they reach their peak, though, you must either consume them immediately or refrigerate them. The refrigerator may give you some time before the tomatoes start to break down and rot, which can happen many hours after the tomato has peaked. And a refrigerated ripe tomato holds up and tastes better than one that has been left out at room temperature beyond its prime, especially if you allow the refrigerated one to return to room temperature before eating it.
And here’s the other thing to know: The refrigerator is not great for tomatoes—it can degrade their texture and dampen their flavor—but it’s far more harmful to lower-quality and underripe tomatoes than it is to truly ripe, delicious ones. Top-quality, in-season, picked-straight-from-the-vine ripe tomatoes store much better than most typical tomatoes from massive industrial operations.
Test 1: Conventional Tomatoes
To run my first tomato experiment, I went out and bought three different varieties of tomato: first, run-of-the-mill hothouse tomatoes—you know, the kind that typically get sliced and served on cheap deli sandwiches; plum tomatoes; and, finally, some cherry tomatoes that came in a plastic clamshell and tried to look fancy by just barely holding on to their desiccated vine. (There’s nothing like a withered, dried-out stem to suggest “farm-fresh.”)
I bought several of each variety, selecting similar-looking specimens to minimize variations in ripeness—fairly easy, given that these were all pretty crappy yet highly invariable mass-market fruit. In terms of relative quality, cherry tomatoes were the best, plums were in the middle, and regular tomatoes were the poorest.
I took them back to my mother’s place, where the central air is set to about 75 to 80°F (24 to 27°C). I placed half of each kind in the fridge and half on the counter.
After 1 Day of Storage
After letting the tomatoes sit in their respective environments for a day, I sat my mom and sister down and asked them to taste and rate my tomato samples, which I served to them blind. I let the chilly tomatoes warm up to room temperature before continue with the tasting to ensure that the cold of the refrigerator didn’t impact their votes.
I could see there were some variances even before I sliced into the tomatoes. The standard tomatoes, for instance, had turned redder on the counter than they had in the fridge, though the difference was subtle. Take note of the yellow specks on the refrigerator tomato’s skin on the right, as opposed to the redder skin on the countertop tomato on the left.
The plum tomatoes showed a similar effect, with the countertop ones (at left in the photo above) redder than the chilled ones to the right. Meanwhile, entire cherry tomatoes were more difficult to distinguish visually.
Once I cut into them, a similar pattern emerged:
Internally, the refrigerated tomato seemed somewhat more yellow and pale than the countertop tomato, yet both were mealy and unripe.
The plum tomato had the most pronounced visual change, with the refrigerated sample’s flesh looking more white and gritty than the countertop sample.
Here’s another close-up of the plum tomato, this time with the chilled sample on the left.
The cherry tomatoes differed the least, with a barely discernible rise in redness in the countertop sample (at left).
What about the taste-test results? Well, first, my mom was disqualified because she kept rejecting all the tomatoes, regardless of storage method, while reminiscing about what they used to taste like in the farmlands of Maryland where she grew up in the ’40s and ’50s.
Thankfully, my sister was able to concentrate on the work at hand—analyzing the relative, rather than absolute, virtues of these tomatoes—and offer me her assessment. In each occasion, the tomato she chose as her favorite was the countertop sample: the refrigerator sample never won. She found the countertop ones to be more aromatic and sweet, with a better texture, than the refrigerated ones, though she said the differences weren’t as apparent with the cherry tomatoes.
My sampling of the samples confirmed her selections, and we both came away with a few observations:
- To begin, no matter how you keep it, a genuinely lousy tomato, such as the ones seen here, cannot be transformed into an excellent tomato.
- A tomato that is good but not spectacular, like the plums I got, might improve greatly from being kept out at room temperature.
- Cold temperatures have less of an impact on better-tasting tomatoes, such as the cherries in this test.
- Another problem raised by my sister: Tomatoes with more flesh and less seed jelly, such as the typical types available here, are more likely to suffer textural deterioration than varieties with very little flesh and more seed jelly, such as the cherries.
So far, my test results were as I’d expected.
The Unexpected Turn After 2 Days of Storage
It was at this point that I thought I’d repeat my tasting after another day, confirm all my findings, and be done with it. So, a day later, I sat down with my family once more—this time my sister, stepfather, and mother (who, I explained to her, could only participate if she forgot about those mythic Maryland tomatoes and focused on the ones in front of her).
I let the refrigerated tomatoes to come to room temperature before serving them beside the countertop tomatoes. But this time, I also stuck some of my countertop ones in the fridge a couple hours earlier, to compare briefly chilled countertop ones to room-temp multi-day-refrigerated ones. All of the tomato samples were served blind.
And the weirdest thing happened: My sister reversed all her picks from the day before, and consistently selected the refrigerated tomatoes as her favorites this time. What?
I sat at the table, perplexed, and requested my sister to serve me the samples blind. Here’s what’s even more weird: Because I had been slicing, smelling, and tasting the tomatoes as I served them, I was able to correctly differentiate the refrigerated and countertop samples every time by smell alone. Even though I could tell them different, I had to agree with my sister—the refrigerated ones were superior in every situation that day.
Hence, in the case of these three varieties of normal store tomatoes, the refrigerator initially made them worse, but with further time, the refrigerated tomatoes improved over the countertop tomatoes.
One explanation for these first test findings is that, since my mother’s house was a warmish 75 to 80°F, the heat began to take its toll on my countertop samples once enough time had passed.
After reviewing some tomato literature, this theory seems to make sense, albeit I haven’t validated it. What most studies have found is that storage temperatures can affect both a tomato’s texture and its volatile aromatics (which are responsible for its complex scent), with colder temperatures degrading the volatiles more quickly.
According to the Department of Plant Sciences at UC Davis, firm, ripe tomatoes should be stored at temperatures ranging from 44 to 50°F (7 to 10°C), which is greater than fridge temperature but lower than most rooms. (The article recommends storing less ripe tomatoes at warmer temperatures, which backs up my earlier finding that riper tomatoes can endure low temperatures while less ripe tomatoes benefit from some warmth.) This French study, meanwhile, found that 4°C (39°F) temperatures are much more harmful to volatiles in the tomato than 20°C (68°F), though it also found that letting refrigerated tomatoes sit out for 24 hours at 68°F reversed some of the ill effects.
But, the research I’ve discovered do not investigate the impact of even higher temperatures on tomato preservation. That may not be a problem for tomato and produce companies with refrigerated trucks and warehouses, but it is a problem for those of us at home, since not all of us with air conditioning have the thermostat set as low as 68°F, or even have it running 24/7; some of us, like me, don’t have air conditioning at all. Given that tomatoes ripen in the summer, the challenge is that we’re trying to store them at home during a season characterized by intense heat, and we don’t usually have storage conditions in the 44-to-50°F range.
This Business Insider piece nicely shows my point: The scientist quoted in the piece, who is recommending that we not refrigerate our tomatoes, casually defines normal kitchen temperature as between 68 and 73°F (20 and 23°C). That’s a frigid kitchen—colder than most of the kitchens I’ve seen in the summer! Unless you’re using your air conditioner nonstop from July to September, it’s probably cooler than your kitchen.
Test 2: In-Season, Local Tomatoes
My initial experiment had some unexpected results, but it was based on just a few types of lower-quality store tomatoes, leaving certain concerns unsolved. Specifically: How does this wisdom apply to really good, farm-fresh tomatoes that are perfectly ripe and ready to eat, and are there any more useful guidelines for storing tomatoes?
To find out, I spent the following several weeks stockpiling all sorts of delicious tomatoes. Every time I went to the farmers market, I’d buy as many tomatoes as I could carry, then leave half on the counter and half in the fridge for at least a day before tasting them.
You’d think that there’d be many studies out there that look at the effects of storage on really great, ripe-picked tomatoes that have come straight from the farm, but as it turns out, most of the research money out there goes toward studying the effects of storage on the average, picked-when-still-green supermarket tomato. My tests would attempt to fill in the blanks.
In all, I ran 11 different rounds of tests, each of which included several types of tomato, from hybrids like beefsteaks to many different heirloom varieties in all shapes and sizes. The tomatoes were all purchased perfectly ripe at the farmers market. I kept half of the tomatoes on the counter and the other half in the refrigerator. I completed eight of the tastings after about 24 hours of storage and the other four tastings after two or more days of storage (with no tastings after longer than four days of storage). To prevent temperature bias, like tomatoes were always compared with like (no pitting a beefsteak against a cherry tomato), and all refrigerated tomatoes were allowed to come to room temperature before serving. Everyone except the server tasted blind while other tasters were present, which was the majority of the time.
Here are the basic results:
- In one out of 11 tests, tasters unanimously chose the countertop tomatoes over the refrigerated ones. This was one of the batches that had been kept for 24 hours.
- Tasters overwhelmingly favored refrigerated tomatoes in five of eleven tests; countertop tomatoes were flat and lifeless in contrast.
- The following five tests either produced divided votes or an inability to distinguish between the two samples. In all instances where the votes were split, no tasters had strong convictions about which tomato was better, so I’m considering all five of these cases in which the refrigerator and the countertop tomatoes were essentially indistinguishable from each other.
These results jibe with my original theory: Because peak-season farmers market tomatoes are already perfectly ripe, they benefit very little from extra time in the heat, and in many cases they are harmed by it, while the refrigerator does minimal harm once tomatoes are ripe. The refrigerator had no discernible effect on the texture of the ripe tomatoes.
Let me leave you with one lingering picture that should demonstrate my thesis on its own. Below, you can see the relative merits of counter versus refrigerator storage at the four-day mark on a pair of tomatoes that started out just about equally ripe. Because of the high-heat atmosphere, the countertop tomato degrades faster.
You could think that’s great. You’ve just shown that tomatoes decay quicker at ambient temperature than in the fridge. Whoop whoop… But that’s exactly the point: If you’re buying your tomatoes ripe (which we should all be doing!) and need to store them for an extra day or two, you’re often better off storing them in the fridge than on the countertop.
Where Do We Stand Now?
The decision of whether or not to refrigerate tomatoes boils down to which is the lesser of two evils. I have little doubt that food experts are correct, and that the best storage temperature for shop tomatoes is between 55 and 70°F (13 and 21°C). Yet I also know that few of us keep our homes at such consistently cold temperatures. Consider yourself fortunate if you have a cool cellar or a wine fridge. I don’t want to see your power bill if your thermostat is always set that low. The rest of us have a choice between a warm (or even hot) counter and a too cold fridge. After your tomatoes are mature, the fridge is typically the best place to store them.
Based on my research, here are some more detailed tomato-storage guidelines:
- Buy just as many perfectly ripe tomatoes as you can consume in a day or two, put them stem side down on a level surface at room temperature, and eat them all within the first day or two.
- If you acquire underripe tomatoes, let them out at room temperature until fully ripened before transferring them to a cooler location for extended storage.
- If you have a wine fridge or cold cellar, keep any ripe tomatoes that you won’t be able to consume within the first day in there.
- If you don’t have a wine fridge or cold cellar, put any ripe tomatoes that you won’t be able to consume within a day in the refrigerator.
- When keeping tomatoes in the refrigerator, place them on a top shelf near the door, which is frequently warmer than the bottom and rear of the fridge.
- If you can’t stomach eating fridge-cold tomatoes and don’t have the time or patience to let them warm up on the counter, you’re going to have to make some difficult choices.
Test 3: In Search of More Data
My tomato experiments were defying the long-held belief that a tomato should never be stored in a refrigerator, but I still needed additional data.
After all, more data is always beneficial, and repeatability is the bedrock of every credible experimental finding. I decided to do further experiments and requested Kenji to conduct some on the West Coast to see whether his findings were comparable to mine. My original observations would either hold or I would have to alter them.
Kenji and I divided the work. Here on the East Coast, I went to the farmers market and purchased a significant quantity of both standard red tomatoes and heritage varieties. ** My plan was to do one giant blind tasting in the office, with as many people as I could wrangle, and more quantitative measures (as opposed to the strictly qualitative assessments I had done earlier in the summer). Then I’d follow that with some triangle tests to see just how well tasters could really differentiate between refrigerated and room-temp samples.
** For anyone wondering whether I purchased bad tomatoes from a wholesaler at the market, it’s worth noting that the NYC Greenmarket permits sellers to sell only food they’ve produced themselves, and that I spoke with the farmers to ensure the tomatoes hadn’t been refrigerated before.
Meanwhile, over yonder in the Bay Area, Kenji went and picked his own tomatoes straight from the vine, just to remove any lingering question about the handling practices of the middlemen. He next conducted his own blind tastings of the tomatoes. He also looked for symptoms of mealiness in the refrigerated tomatoes.
So, what were our findings? Shocker! The refrigerator still isn’t as evil as the never-refrigerate rule makes it seem.
My East Coast Tests
It was the height of summer in New York City when I conducted my first set of experiments, with temperatures far over 80°F (27°C). Without air conditioning in my apartment, I found that more often than not, refrigerated ripe tomatoes tasted better than ones that continued to sit out on the counter, suggesting that in instances in which room temperature was above roughly 80°F, refrigeration was often preferable. ***
*** Remember, I had found several scientific studies that compared refrigeration to “room-temperature” conditions, in which the room-temp conditions were all below 70°F (21°C), colder than many summertime rooms in real life; I hadn’t found a single study that compared refrigeration to warmer storage conditions. I also found no studies that looked at fully ripe tomatoes; they all appeared to be developed with large-scale tomato producers in mind, who harvest their tomatoes when they are still green, rather than those of us at home.
As I went out to do the current series of testing, temperatures in New York had dropped significantly, to the 60s and 70s. My whole argument was on very hot summer temperatures, and I made no claim that the refrigerator was equivalent to or better than temperatures in the 70s and lower. With the weather changing, I wasn’t sure what I’d see this time.
The Blind Tasting
As previously said, I purchased a variety of tomatoes from the farmers market. The majority of them were standard red slicing tomatoes, with the remainder being a mix of heirlooms. Their quality was inconsistent. I placed half of each tomato kind in the refrigerator and the other half on the counter. The next day, I took the refrigerated ones out and let them come back up to room temperature.
I then chopped up each tomato and numbered them. I had 10 tasters go through the samples, each in a different sequence, to guarantee that no single tomato suffered from palate fatigue. Tasters rated the tomatoes on four categories, from one to ten: overall preference, taste, scent, and texture. The overall-preference score aligned almost exactly with the other scores, so the below chart shows the overall-preference score, since the others look pretty much the same:
Before I go into the details, I want to emphasize that this test contrasted tomatoes kept at low 70s temps versus refrigerated tomatoes, basically pitting refrigerated tomatoes against considerably more favorable settings than in my earlier experiments.
Instead of an obvious and unambiguous difference, the differences between refrigerated tomatoes and counter tomatoes were quite tiny. Except for the little yellow heirloom tomatoes, where the refrigerated tomatoes obtained the highest average score, the counter tomatoes only slightly beat out the refrigerated ones. That was also the highest average score of all the tomatoes, which means that even when compared with much more ideal conditions, refrigerated tomatoes are capable of coming out on top: absolutely not what we’d expect if refrigeration were really as bad as the common wisdom claims.
All of us (the 10 tasters including myself) agreed unanimously that the little yellow tomatoes—the ones that scored the highest in the fridge and out—were the best.
However, the basic red tomatoes had the lowest overall quality, and they were also the group in which the refrigerated tomatoes scored the lowest. This lends further support to my theory that the higher-quality and riper the tomato, the less harm the refrigerator will do to it.
Simply said, truly nice, ripe tomatoes keep well in the refrigerator, but lower-quality tomatoes stay bad or become worse: underripe tomatoes stay underripe, and mealy tomatoes get mealier.
Another critical point: the graphic above depicts average scores. Nonetheless, there was significant variation within each group. Individual refrigerated samples of red tomatoes, for example, scored as high as 5.5, whereas countertop tomatoes scored as low as 3.6. So while the countertop tomatoes slightly edged out the refrigerated ones when averaged together, the distribution of individual tomato scores was much less consistent, regardless of storage method. This, too, suggests that the fruit itself is the bigger factor in how it will handle storage conditions, not some blanket rule about the storage conditions themselves.
The Triangle Tests
The triangle test follows, which assesses if blind tasters can identify the unusual sample after many rounds of tasting. I wasn’t totally convinced there was an advantage to this test: I had never claimed that refrigerated tomatoes were going to always be indistinguishable from room-temp ones. In my previous studies, we were unable to distinguish between refrigerated and unrefrigerated products roughly half of the time. But in the other instances, the differences were apparent; it’s just that in those cases, we tended to like the refrigerated ones more.
Nonetheless, I reasoned that there was no danger in doing a triangle test. I gave Max a trial run one night, using some of those not-so-great red tomatoes I had stashed away. Max has an excellent palette, so I was interested to see how he would fare. In each tasting round, I presented Max with three slices of tomato in random order (either two refrigerated and one countertop, or two countertop and one refrigerated), and his task was to see if he could figure out which of the three was the odd one out. Max has accurately recognized the odd tomato six times after 12 rounds, which is slightly better than chance. (In a triangle test, random guessing should produce right answers one-third of the time, or four out of the twelve rounds.) When he correctly identified the tomato samples, he chose the counter sample(s) as his choice.
When he got it wrong, though, he occasionally preferred chilled slices. This is consistent with the blind-tasting findings: Even though the red counter tomatoes edged out the refrigerated ones overall, there were individual refrigerated samples within the mix that scored higher than some of the counter samples.
But 12 rounds isn’t enough, so the next day I bought even more tomatoes, refrigerated half overnight, and then lined up five different tasters for a new session of triangle testing, with 24 rounds total. We’d expect random guessing to be right eight times out of 24 rounds (one-third of the total number of rounds). My tasters had been accurate nine out of 24 times by the conclusion of my session, performing only a hair over the random-guessing rate.
To be honest, while I was slicing the tomatoes for these tests, I thought the variations were more noticeable, but I knew which was which. (In some situations, I believed counter tomatoes were superior; in others, I thought refrigerated tomatoes were superior.) What this test shows is that once that knowledge is removed, the differences can be subtle enough that tasters have a very hard time telling refrigerated and countertop tomatoes apart. So, while I don’t believe that room-temp and refrigerated tomatoes are totally indistinguishable, these tests indicate that the claims of horrible effects of refrigeration on ripe tomatoes are exaggerated.
On the Value of Science and the Danger of Misusing It
During my tomato-tasting adventure, I’ve thought a lot about the role of science in all of this.
Science has never done anything wrong: It’s a beautiful system—the best one we’ve got—for answering questions about how pretty much everything in the observable universe works. But it’s easy for us to misuse it, and I think it’s just such a misuse that created this inflexible rule about tomato storage in the first place. Please bear with me while I explain:
As I previously said, all of the academic studies I discovered on tomato storage were based on a specific set of conditions: tomatoes selected when they were underripe and kept at temperatures below 70°F. The studies concluded, and I think they are true, that refrigeration harms tomatoes and that they are best preserved at somewhat higher temperatures, in the 50s and 60s. The studies I saw did not look at tomatoes that were selected when completely ripe, and they did not take into account higher storage temperatures, especially those above 80°F.
So, what comes of these studies? This is just a scenario I’ve made up, but it’s plausible to me, and it shows how the further we get from the original data, the more likely it is that the data will be misinterpreted: The big-ag tomato growers follow the research and begin storing their underripe tomatoes in cool temperatures (but not as cold as a refrigerator), and wholesalers do the same. The vegetable dealer learns that refrigerating the tomatoes is detrimental for them. The vegetable dealer then informs the buyer that refrigerating tomatoes is unhealthy for them.
But here’s the rub: Although the don’t-refrigerate advice worked well throughout the supply chain, it doesn’t always apply to the retail consumer, who may have different storage conditions at home, or to tomatoes harvested when ripe—conditions that had not been examined in any scientific research I discovered.
Another example of the misuse of science is in this Alton Brown Facebook directive: “Do me a favor: Never put tomatoes in the refrigerator,” he implores. “If they drop below 50 degrees F, a flavor compound called (Z)-3-hexenal is just going to flip itself off like a chemical switch … permanently.” Oh no, (Z)-3-hexenal is permanently turned off? It sounds terrible.
Assume this (Z)-3-hexenal fact is correct. So, what’s the point? In a complex biological structure like a tomato, am I supposed to believe that because one single aroma molecule goes dormant, that’s therefore a good enough reason to never refrigerate a tomato? What about the tens of thousands of additional intricate processes that occur in a tomato as it ages? How can we possible derive a useful conclusion from a single element in such a complex system as a tomato?
This is an issue in a lot of scientific journalism: Scientists do research and publish their findings. Lay publications, looking to make that information relevant to the lay person, try to find some kind of practical advice buried in the findings. Scientists have discovered that vitamins are essential to the human body? Take them in pill form! Scientists have discovered that fat is harmful? Stop consuming fat! Scientists have discovered that fat isn’t as terrible as previously assumed. Quit eating carbohydrates!
The problem isn’t necessarily with the scientists; it’s with the people trying to give concrete advice about how to live and act based on the work of the scientists. That often gets us into hot water.