Vine-ripe tomatoes. The phrase conjures images of deeply colored crimson fruit near bursting with juices and flavor. Dream on.
Vine-ripe tomatoes are usually picked when they show the first signs of changing color, at what is called the "breaker" stage. That means they're still mostly green: Not more than 10% of the surface has turned red. Because tomato color changes so rapidly at that point, they are sometimes picked to as much as what is referred to as 50% color.
Scientists who study tomato flavor insist this is no big deal. Tomatoes continue to ripen off the vine and, they say, all of the components necessary to make a great tomato are present when the first blush of orange appears at the blossom end.
"A vine-ripe can ripen into a tomato that is nearly indistinguishable from what it would have been if it had been left on the vine," says Marita Cantwell, post-harvest specialist at UC Davis. "That is, if the tomato is properly handled--if it is kept between 55 and 65 degrees during ripening."
Ed Beckman of the California Tomato Commission says he once slipped a vine-ripe into a tasting held by a group of Fresno master gardeners. "They couldn't believe it when they found out. It's just an example of what we could do if we had an ideal world. These were tomatoes that hadn't gone through the distribution system."
The tomatoes known as "mature-greens," which make up 80% of the harvest, are another matter. Theoretically you can end up with a good tomato, but in practice that is hard to do.
"If you have a very well-developed mature-green, one that is already beginning to develop color inside with the seed cavities well filled with gel, that tomato can have a similar volatile profile to a vine-ripe," Cantwell says. "But a typical mature-green has less quantitatively of all of the important volatile aromas."
That's partly because it is difficult to tell a fully developed mature-green tomato from one that is immature. Because there is no external color change it is hard to tell when the tomato is ready to pick. Growers usually cut open a few tomatoes to check. And since fields are harvested in one clean sweep, what you end up with are some tomatoes that are ready to be picked and others that are not.
Mature-green tomatoes are almost always treated with ethylene gas, a natural gas given off by fruits and vegetables during the ripening process. "They will eventually ripen on their own, but it would take so long that they would be of inferior quality by the time it got done," Cantwell says. "Ethylene gas both triggers the ripening process and, since the tomatoes are at all different stages when they're gassed, it gets them ripening at the same rate."