Whether it's soups and stews, steaks and salads or just good old pasta sauce, the humble tomato is a ubiquitous part of the western diet. And deservedly so — they're cheap, healthy and delicious. Now, things might be about to get a whole lot better. According to researchers, some simple steps in commercial processing could dramatically improve the flavor of commercially sold tomatoes.
As any shopper will tell you, even when they are kept in the fridge, tomatoes don't exactly have the longest shelf life. In these days of mass production, your dinner plate can be the end of a very long journey. The industry prevents tomatoes from becoming too ripe before they reach the store by picking them when they are still green. The fruit is then forced to ripen by dousing it with ethylene — a naturally occurring gas that is produced by a number of ripening fruits —before it is stored and shipped at low temperatures.
This chilling process certainly makes the tomatoes last a lot longer — the problem is that it also diminishes its flavor. This is why the ones you get from your own garden or the local farmers' market taste so much better than store-bought tomatoes, which can taste watery and insipid. Dr. Jinhe Bai, a research plant physiologist at the Agricultural Research Laboratory in Florida, and his team have developed a slightly different method in an effort to improve the flavor quality.
"Ideally, tomatoes should be picked ripe and then sold immediately, as they are at farm stands," says Bai who is about to present his flavor-saving research in Boston to the 250th National Meeting & Exposition of the American Chemical Society (ACS). Unfortunately, such a quick turnaround isn't always possible. Commercially sold tomatoes are often stored and then shipped over long distances.
According to the United States Department of Agriculture (USDA) — 71 percent of tomatoes imported into the U.S. come from Mexico while over three-quarters of U.S. fresh tomato exports are shipped to Canada, Mexico and Japan. The U.S. is the world's second largest producer of tomatoes, where they are grown in 20 states — according to the USDA, 89 percent of all tomatoes produced in 2008 were machine-harvested.
That's a lot of chilled, flavorless fruit. "To produce a better tasting tomato," says Bai, "we added a hot water pre-treatment step to the usual protocol that growers follow." The team — from the U.S. Department of Agriculture, Agricultural Research Service and the University of Florida — dipped Florida-grown green tomatoes in water heated to about 125 degrees Fahrenheit for five minutes and then let them cool at room temperature. Next, they chilled the fruit to between 41 and 55 degrees Fahrenheit — the same range commercial producers use for shipping. After the tomatoes fully ripened, the researchers tested them for flavor and aroma.
They found that tomatoes heated before chilling had higher levels of flavor compounds (6-methyl-5-hepten-2-one, 2-methylbutanal and 2-phenylethanol) than non-heated fruit, and they tasted better, Bai says. "Chilling suppresses production of oxygen, nitrogen and sulfur-containing heterocyclic compounds, ketones, alcohols and aldehydes, including 13 important aroma components of tomato flavor. But hot water-treated fruit actually produced higher concentrations of these important aroma contributors, even with subsequent chilling."
Bai says theirs is an inexpensive fix to the flavor problem. Many methods of preservation sacrifice flavor to prevent spoilage, he points out. "Our methods can easily be implemented in the current commercial system without risking fruit decay," he explains. "We found that this pre-treatment step prevents flavor loss due to chilling." As well as measuring how long-lasting the tomatoes are, the team is presently monitoring flavor compounds at different time points: when the fruit are green, soon after the process is performed and when they are partially ripened. This information, they say, will be combined with the data on fully ripened tomatoes to help the team develop a better commercial process.
The scientists have also looked at other methods of preservation. The first involved incubating green tomatoes with methyl salicylate — wintergreen oil — an antifungal fumigant that is "generally recognized as safe" by the FDA. Another involved picking the tomatoes at a later stage. Instead of collecting them when they were all green, the researchers waited until they were half-green and half-pink — the "breaker stage" — and treated them with 1-methylcyclopropene, making them tolerant to higher temperatures and so avoiding the need to chill.
The researchers say they will closely compare the benefits of all techniques to determine which is better before approaching food processing firms to determine whether they are interested in adopting the technique. Maybe the new batch of tomatoes can slow a worrying trend highlighted by the USDA. According to their figures, Americans consume three quarters of their tomatoes in a "processed form." This trend, they say, "accelerated in the late 1980s with the rising popularity of pizza, pasta, and salsa."
Though it may be quicker and easier to opt for ready-made pasta sauce or pizza, it's definitely worth bearing in mind all the extra salt, sugar, high-fructose corn syrup, colorings and other additives you could be eating along with it. "About one-third of all processed-tomato products are purchased away from home at various foodservice outlets," the USDA says. You know in your heart fresh is best — so while you're waiting for those tasty new tomatoes, why not check out our guide on how to pick the perfect tomato and then add some extra flavor by dishing up our gazpacho with lump crab and avocado, vegetarian loaded nachos or the ultimate heirloom tomato tart.