na.ked [nay-kid] adj.- “exposed to view or plainly revealed“
The tomato (a.k.a., Solanum lycopersicum).
What are the chemicals that make most homegrown tomatoes taste so good?
What is the genome sequence of the domesticated tomato? And how is it related to wild relatives, and even to potatoes?
These interesting and complex questions have been answered – mostly – just in the past few weeks.
So it’s been a pretty good time for people curious about the tomato.
Here’s a summary of the findings.
Better Tomatoes Through Psychophysics
But, in this case, I think it means to attempt to accurately measure which chemical compounds in tomatoes lead most people to perceive good taste or flavor.
Pyschophysics is tough to clearly explain. Perhaps the best explanation was provided by Malcolm Gladwell.
Anyway, back to the question: What’s the chemical difference between the tasteless supermarket tomatoes that you buy in the winter and the vine-ripened, heirloom varieties of tomatoes that you grow or buy at the farmers market in the summer?
It turns out this is way more complex, chemically, than you might think.
Researchers primarily at the University of Florida, Gainesville, discovered that a large chemical diversity exists among heirloom varieties of tomato. They saw this, however, as an opportunity to discover which chemicals in a ripe tomato are most important for the “best tasting” tomatoes.
Briefly, after determining so-called “consumer liking scores” for both heirloom and supermarket tomatoes, they found that, aside from sweetness due to sugars, there was a high chemical complexity involved in “liking” a tomato. In other words, there is no simple answer regarding which chemicals made for a “good tasting” tomato.
They did, however, find that “…some of the most abundant volatile chemicals found in tomatoes do not contribute to consumer liking, whereas other less abundant ones do.”
Indeed, by genetically removing specific chemicals from tomato fruits, they found that “…volatiles previously predicted to be the most important contributors to tomato flavor based on odor units have no significant impact on consumer liking.” (from Ref 1 below)
Surprisingly, they found some volatile chemicals enhanced the “sweet perception” by tasters, suggesting the possibility that “…these volatiles could be used as a replacement for a portion of the sugars used in processed foods, thus reducing caloric content.”
By using traditional plant breeding methods, these researchers can now try to intensify the “flavor” volatiles in the high-yielding, tasteless supermarket tomatoes. (Listen to an interview with Prof. Harry Klee about this study here – with thanks to The Naked Scientists.)
These efforts will be greatly assisted by the recent publication of the genome sequence of tomato.
Since 2003, a team of nearly 300 scientists in 14 countries have been working on sequencing the tomato genome.
They not only published a high-quality genome sequence of the domesticated tomato, but also a draft genome of its closest relative, and they compared those to the potato genome sequence. (Potatoes are in the same plant family as tomatoes, the Solanaceae.)
The two tomato genomes are 99.4% the same, but show more than 8% divergence from potato. One of the most interesting findings was that the entire tomato genome was copied in triplicate on two separate occasions, and the second event (around 60 million years ago) had major implications for the development of the fruit.
The information provided by this study will be invaluable to tomato breeders providing “… biological knowledge and empowering biodiversity-based breeding.” (from Ref 2 below).
Bottom Line: Thanks to all this newly-published research, someday we may all be able to buy really good tasting tomatoes in January.
1. Tieman, D., et al. (2012) “The chemical interactions underlying tomato flavor preferences.” Current Biology, Vol. 22, pp. 1035-1039. (Abstract)
2. The Tomato Genome Consortium (2012) “The tomato genome sequence provides insights into fleshy fruit evolution.” Nature, Vol. 485, pp. 635–641. (Full Text)
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