By Dr. Mercola
There's not much in the produce world that can compare to the flavor of a fresh-picked tomato. But this flavor – that to some portrays the very essence of summer – is extremely vulnerable.
If you purchased your tomatoes at a grocery store, they probably weren't ripe to begin with (they're typically picked a few days before they're fully ripened to make them easier to ship). If you put an unripe tomato in your fridge, the ripening process will stop, so you'll certainly be left with a tasteless tomato.
But even if your tomatoes were homegrown or picked up from a local farmer's market (arguably the best sources of truly flavorful tomatoes), their flavor will quickly disappear if you put them in the refrigerator, due to a change in chemical structure.
Volatiles: The Secret Behind Tomato Flavor
The flavor of a tomato is a result of an interaction between sugars, acids, and multiple volatile compounds. Volatiles are responsible for making a tomato taste like a tomato, and while there are several hundred of them in this fruit, only 15-20 actually impact our perception of its flavor.1 As explained by the University of Florida:2
"This is because most of these compounds fall below the odor threshold. This threshold is determined by both the concentration of the substance and our ability to detect it. Thus, a compound that is present in quite high levels that we detect poorly will not register. Conversely, a substance to which we are quite sensitive will be perceived in very low amounts."
For example, following is a list from the University of Florida of some of the major volatiles in tomatoes, along with their concentration and odor characteristics.3
Volatile Concentration (parts per billion) Odor Characteristics cis-3-Hexenal 12,000 tomato/green ß-ionone 4 fruity/floral hexanal 3,100 green/grassy ß-damascenone 1 fruity 1-penten-3-one 520 fruity floral/green 2+3-methylbutanal 27 musty trans-2-hexenal 270 green 2-isobutylthiazole 36 tomato vine 1-nitro-2-phenylethane 17 musty, earthy trans-2-heptenal 60 green phenylacetaldehyde 15 floral/alcohol 6-methyl-5-hepten-2-one 130 fruity, floral cis-3-hexenol 150 green 2-phenylethanol 1,900 nutty/fruity 3-methylbutanol 380 earthy, musty methyl salicylate 48 wintergreen
Store Your Tomatoes on the Counter – Not in Your Fridge
If you've ever stored your tomatoes in the fridge, you may have noticed a change in both their taste and texture. This isn't a coincidence but rather is a direct result of the cold temperatures on the tomato's volatiles (and texture). Researchers in France have revealed that storing a tomato at room temperature (68 degrees F) allows it to not only maintain its existing volatiles but also to produce more of them.4
This implies that the flavor of a tomato left to ripen on the counter will only continue to improve (to a point, of course). If you want your tomatoes to continue to ripen, the ideal temperature range is 65-70 degrees F (although temperatures of 57-61 degrees F are often used for "slow ripening" when tomatoes are in transit).
On the other hand, when a tomato was stored at refrigerator temperature (39 degrees F) during the study, its volatiles begin to break down. Volatiles associated with green and grassy notes were those hardest hit, which explains why refrigerated tomatoes lack that fresh-picked flavor. The researchers noted:
"Storing tomatoes at 4°C [39 degrees F] induced a drastic loss in volatiles, whatever their biosynthetic origin. After 30 days at 4°C, the concentration of volatiles had decreased by 66%… Storing tomatoes at fridge temperature, even for short durations, was detrimental for their aroma."
If you've put your tomatoes in the fridge by mistake, there's a trick that might help to bring back some of their flavor: let them sit at room temp for 24 hours before eating. The researchers found that tomatoes left to "recondition" at 68 degrees F for a day were able to recover some of their aroma production, even if they'd previously been refrigerated for up to six days. Another option? Use up refrigerated tomatoes in a sauce recipe, where the added flavors from onions, garlic, and basil are likely to cover up the tasteless tomato.
Tomatoes Are Very Susceptible to Chilling Injury
If a tomato gets too cold, not only will its flavor be affected but also its texture, color, ripening potential, and much more. Any temperature below 50 degrees F can injure a tomato, and this may occur at any stage of production, including in the field prior to harvest or later when it's put in your fridge. The Postharvest Technology Center at US Davis explained the consequences of chilling injuries to tomatoes:5
"Tomatoes are chilling sensitive at temperatures below 10°C (50°F) if held for longer than 2 weeks or at 5°C (41°F) for longer than 6-8 days. Consequences of chilling injury are failure to ripen and develop full color and flavor, irregular (blotchy) color development, premature softening, surface pitting, browning of seeds, and increased decay (especially Black mold caused by Alternaria spp.). Chilling injury is cumulative and may be initiated in the field prior to harvest."
The Paper Bag Trick for Ripening Green Tomatoes
If you're a tomato gardener, you may have found yourself with green tomatoes left on the vine at the end of the season, with a frost threatening. Rather than leaving them to rot, pick the green tomatoes (include those that are partially red or yellow) and put them in a brown paper bag (be sure to fold the top over to close it). As the tomatoes ripen, they will release ethylene gas that will help the other tomatoes to ripen quickly. Just make sure to check the bag daily to remove fully ripe (or overripe) tomatoes. This is a simple trick for ripening not only green tomatoes but also those that may be under-ripe when you pick them up from the store.
Tip: Organic Tomatoes Are More Nutritious
Tomatoes, which are actually a fruit and not a vegetable, contain a number of valuable nutrients, and according to research, organically grown tomatoes are even more nutritious than their conventionally grown counterparts. One study found growing tomatoes according to organic standards results in dramatically elevated phenols content compared to tomatoes grown conventionally, using agricultural chemicals.
The organic tomatoes were found to contain 55 percent more vitamin C and 139 percent more total phenolic content at the stage of commercial maturity compared to the conventionally grown tomatoes.6 There was a trade-off, and that was size. The conventional tomatoes were significantly larger. However, while many unaware consumers equate size with quality, this simply isn't the case. At least in the case of organic tomatoes, you get more even though it may be in a smaller "package."
Lycopene and Other Health Benefits of Tomatoes
There's good reason to regularly include tomatoes in your diet, as they are rich in flavonoids and other phytochemicals that have anti-carcinogenic and other healthful properties. They're also an excellent source of lutein, zeaxanthin, and vitamin C (which is most concentrated in the jelly-like substance that surrounds the seeds) as well as vitamins A, E and B-complex vitamins, potassium, manganese and phosphorus. Other lesser-known phytonutrients found in tomatoes include:
- Flavonols: rutin, kaempferol, and quercetin
- Flavonones: naringenin and chalconaringenin
- Hydroxycinnamic acids: caffeic acid, ferulic acid, and coumaric acid
- Glycosides: esculeoside A
- Fatty acid derivatives: 9-oxo-octadecadienoic acid
Tomatoes are also a particularly concentrated source of lycopene — a carotenoid antioxidant that gives fruits and vegetables like tomatoes and watermelon a pink or red color. Lycopene's antioxidant activity has long been suggested to be more powerful than other carotenoids such as beta-carotene, and research has revealed it may significantly reduce your stroke risk (while other antioxidants did not).
It's estimated that 85 percent of dietary lycopene in North Americans comes from tomato products such as tomato juice or tomato paste.7 In addition to lowering your risk of stroke, lycopene from tomatoes (including unsweetened organic tomato sauce) has also been shown to be helpful in treating prostate cancer. If you eat ketchup, choose organic ketchup, as it has been found to contain 57 percent more lycopene than conventional national brands.8
Why Cooked Tomatoes May Actually Be Healthier
While I recommend consuming a good portion of your fruits and vegetables raw, tomatoes are one exception where cooking may enhance their nutritive value. Research shows that cooking tomatoes (such as in tomato sauce or tomato paste) not only increases the lycopene content that can be absorbed by your body but also increases the total antioxidant activity. In one study, when tomatoes were heated to just over 190 degrees F (88 degrees C) for two minutes, 15 minutes and 30 minutes:9
- Beneficial trans-lycopene content increased by 54 percent, 171 percent, and 164 percent, respectively
- Levels of cis-lycopene (which is a form easily absorbed by your body) rose by six, 17, and 35 percent, respectively
- Overall antioxidant levels increased by 28, 34, and 62 percent, respectively
As an aside, I realize that canned tomatoes are a popular product, especially for making tomato sauces, but it's better to use fresh for this purpose. Canned tomatoes typically have a lining that contains bisphenol-A (BPA), which is a potent endocrine-disrupting chemical that has been linked to a number of health problems, including diabetes, heart disease, heightened risk of breast and prostate cancers, neurological effects, reproductive problems, and obesity. Finally, it's best to consume your tomatoes, whether raw or cooked, with some type of fat, such as olive oil, since lycopene is a fat-soluble nutrient.
Visit Our Food Facts Library for Empowering Nutrition Information
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