Tomatoes are probably the most popular of all garden vegetables. Whether you pick up a flat of hybrid tomato plants at the local garden centre or shop online for heirloom tomato seeds in yellow, orange, green, purple, and red, you are probably growing at least one variety of tomato in your vegetable garden. And right about now, those tomatoes are ripening. Lots of tomatoes are ripening.
Do you find yourself scrambling to use them all up before they spoil? If you’re like most people, you’re up to your eyeballs in tomato sauce, stewed tomatoes, and BLT sandwiches right now. And you probably still have more ripe or almost-ripe tomato fruit that you don’t know what to do with. I bet you’ve been told you should never put those tomatoes in the fridge. I bet you’re also really tempted to do it!
So here’s the question: is it ever OK to refrigerate tomatoes? I know a lot of gardeners and cooks who are really serious about never storing tomatoes in the fridge. But does science bear out all the warnings about destroying the flavour of tomatoes if we keep them in the fridge? This week, I took some time to dig around a bit on the internet instead of in the garden. Let me share what I learned about storing tomatoes the best way to preserve their flavour.
Traditional Advice for Storing Tomatoes
I love chef Alton Brown because he talks about the science of foods. He doesn’t just teach a traditional cooking method or offer a recipe and expect people like you and me to blindly follow it, simply because he’s a chef and that’s how he does it. In fact, sometimes he makes a point of talking about the traditional advice and then he recommends that you do exactly the opposite!
Alton talks about how different ingredients contribute to a recipe and he brings in experts who can explain the scientific phenomena in everyday language. So when Alton makes a recommendation about a particular food, I tend to sit up and take notice. And when it comes to those lovely red beauties from our gardens, he agrees with the conventional wisdom about storing tomatoes in the fridge.
Do me a favor: Never put tomatoes in the refrigerator.
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.
The Zed‑what? And what does he mean when he says it will switch itself off? What does that do to your tomatoes?
In order to answer that question, we first have to look at some of the components that contribute of tomato flavour. As we do this, you’ll see where this hexenal stuff fits into the bigger picture. Follow me for a quick tour of tomato taste!
What Makes a Tomato Taste Good?
The flavour of a tomato is a complex question. In large part, it’s determined by the balance between the sugar content and the acidity of the fruit. Tomato flavour is also impacted by a group of volatile compounds which are associated with smell, taste, and even the colour of the fruit.
“Volatile” means these chemicals evaporate easily at room temperature. They are released when we brush up against the leaves of many plants, when we pull a ripe tomato off the vine, and when we slice or bite into a fruit. Essential oils used for aromatherapy and holistic medicine are also known as “volatile oils.” They are a kind of volatile aromatic compound that is extracted from plants. You could think of them as a bottled version of the many different compounds that occur naturally in the plant.
Volatile compounds in food plants help to ensure a plant’s survival by attracting pollinators or repelling insects that would cause damage. They also serve to attract our attention and signal us that a plant is good for food. Science is just beginning to understand the more than 400 volatile compounds in tomatoes. But we are already able to see that they play a key role in how we perceive the taste of a tomato, and in whether or not we are satisfied with that flavour.
How Volatile Compounds Impact Tomato Taste
Volatile compounds are not themselves sweet or acidic, although some of them can change how we perceive the taste of a tomato. Everyone has personal preferences when it comes to tomato flavour, but most people tend to like tomatoes that taste sweet.
This can mean that the tomato has a high sugar content that can be measured in Brix – for example, a ‘Candyland Red‘ currant tomato or ‘Fantastico’ measured at 12 °Bx, or a Brandywine heirloom tomato with a whopping 14 °Bx, all of which are as sweet as any fruit. But a tomato may also have a lower actual sugar content and still be perceived as sweet because it also has low acidity. Certain volatile compounds like geranial can also make a tomato seem sweeter, regardless of the balance of sugar and acid in its fruit.
Why Your Fridge isn’t the Best Place for Tomato Storage
So what does all this have to do with where you store your tomatoes? Was Alton right? And what is this hexenal stuff, anyway?
Let’s start with the volatile compound itself. What Alton calls (Z)‑3‑hexenal is also known as cis‑3‑Hexenal, or sometimes just 3‑hexenal. It belongs to a group of chemicals known as aldehydes, which you may be familiar with if you know a little something about perfumery. Aldehydes are strongly associated with Chanel No. 5, which relies on them to lift its floral foundation.
3‑Hexenal is an aldehyde with a sharp green scent that is associated with the smell of freshly cut grass. It can be found in many food plants, including apples, cucumbers, berries, and even black tea. It is also present in the leaves and fruit of the tomato plant. It also happens to be one of the most abundant volatile compounds in tomatoes, which may be why Alton Brown makes specific mention of it in his tomato storage advice.
The leaf aldehyde, as it is sometimes called when discussing it as an aroma compound, is actually just one of over 400 volatile components that have been identified in tomatoes. These compounds begin to develop when the fruit starts to ripen and we know that they contribute to the taste, smell, and texture of a ripe tomato – or what is sometimes just called the “flavour.” We don’t fully understand the role of all these 400 odd chemical components of the fruit. But it does seem that in cases where they are missing or only present in small amounts, the tomato’s flavour and even its appearance can suffer.
And this is the reason we’re concerned about storing tomatoes in the fridge. You see, the volatile compounds in a tomato are reduced when that tomato is subjected to the cold – even though its sugar and acid content remain constant. So when we bite into that tomato, it doesn’t satisfy us the way it normally would. In fact, some scientists have found that if a tomato is held at temperatures below 12°C, the volatile compounds can actually be switched right off. This is what Alton is talking about.
If a tomato is not fully ripe, storing it in the cold can prevent it from ripening and developing its flavour. And if any tomato is kept too cold for too long, it can develop what’s called a chilling injury – the same sort of damage that occurs when plants in your vegetable garden are hit by frost. So we want to be sure to let unripe tomatoes sit out at room temperature in order for them to ripen properly. And once ripe, we want to be careful about how we store them. It’s best to eat ripe tomatoes within a couple of days, or to process them for later use. You can keep your tomatoes fresher for a bit longer if you flip them over and store them with the stem scar down.
Is it Ever OK to Store Tomatoes in the Fridge?
If at all possible, store tomatoes in a cool spot out of direct sunlight. They fare best at temperatures between about 12°C to 20°C – that’s 55°F to 70°F, for those who still prefer the Fahrenheit scale. If your kitchen is much hotter than 20°C, you may want to store your tomatoes in a cool pantry or a wine fridge designed to keep the temperature cool rather than cold.
If there really isn’t anywhere in your home that is cool enough, you may just find that you have to store ripe tomatoes in the fridge. Leaving them out in a very warm kitchen only hastens the processes that lead to rotting. So if you aren’t able to eat or process them hast enough, you can extend their shelf life by a few days by putting them in the warmest part of your fridge – usually near the front of the top shelf.
Scientists have discovered that tomatoes stored in the fridge can be reconditioned. Remove them from the fridge 24 hours before eating and leave them on the kitchen counter to warm up. This restores some, but not all, of the volatile compounds that are lost when the tomato is refrigerated. This reconditioning process works on fully ripe tomatoes that were stored at 4°C for up to 6 days.
So if you can avoid refrigerating your tomatoes, follow Alton’s advice and keep your tomatoes at room temperature. Storing under-ripe tomatoes in the fridge may prevent them from ripening, and even ripe tomatoes can suffer from chilling damage that will turn their texture mealy and rob them of their full flavour. But if you’ve just brought in a huge harvest from your heirloom vegetable garden and you can’t possibly process all the tomatoes fast enough, it’s OK to put the fruit in your fridge to keep it from rotting. This will give you a few extra days to make your tomato sauce or slice your tomatoes for drying in your dehydrator.
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Original content © 2017 Kyla Matton Osborne, aka #RubyWriter
This article was published on my food blog, 24 Carrot Diet. If you are reading this content anywhere else, it has probably been stolen. Please report it to me so I can address any copyright infringements. Thank you!
Featuring public domain photos by Pixabay users magdus, Meditations, Colliefreund, ponce_photography and others