US: Why traditional tomatoes have more flavour
Though the consumer might find the appearance of the modern tomato variety more appealing than some of the older varieties that ripened differently and were not blemish free, they often do not taste as good.
There is some hope that breeders may, in future, be able to put the flabout back into the tomatoes by using the flavour rich heirloom tomatoes, that have a higher sugar content.
"When you have fruit or berries and you sprinkle sugar on top to accentuate the flavors, you can see how every little bit helps," said Ann Powell, a biochemist at the University of California, Davis. Our sensitivity to sweetness makes a gene for sugar production extra-important. "By knowing which gene it is, breeders can now select for varieties when plants are young."
Powell went looking for the reason that the flavour was lacking in the modern tomato varieties and found a protein called GLK. GLK has been known for a while to exist in the leaves of the tomato plant - it's what the plant uses to photosynthesise - but not in the fruits.
Now it appears that the fruits of tomato plants also contain a GLK protein, which boosts sugar production just enough to make a real flavor difference. The dark green shoulder of a tomato - bred out of the most modern varieties - is a sign that extra photosynthesis is happening. Chemical analyses showed that tomatoes with normal GLK proteins also contained more lycopene, an antioxidant that gives tomatoes their red color.
Once tomatoes turn red, though, it becomes impossible to tell which fruits have the mutation, making it highly unlikely that a supermarket shopper would be able to pick out tomatoes with naturally higher levels of sugar.
In fact, the chances of unmutated tomatoes showing up in any major grocery store are extremely slim. When Powell and colleagues looked at 25 commercial varieties of tomatoes from all over the world, they found the exact same mutation in all of them.
"The mutation they describe in their paper is in literally 100 percent of modern breeds sold in grocery stores today," said Harry Klee, a molecular geneticist at the University of Florida, Gainesville, who studies the chemistry and genetics of flavor in fruits and vegetables. "It's a really good illustration of some of the problems with modern breeding of tomatoes."
The GLK mutation isn't the only reason why supermarket tomatoes are so often tasteless, Klee added. But it's an important reason, and it demonstrates how focusing on aesthetics can end up sacrificing other important qualities in an entire generation of produce.
"When you focus on one thing and neglect the other — the other being flavour — you can have some really bad unintended consequences," Klee said. "The consumer is going to have to realize that their tomatoes may not look perfect. There may be a patch of green around the top of the fruit. But to me, I would say, if I see that a fruit is not perfectly red and perfectly uniformly ripened, maybe it's going to taste better."
Source: www.msnbc.msn.com