Ever wonder what makes a
good tomato taste so great? Well, so do
the plant geneticists trying to produce the “better” tomato. The amount of sugar has a lot to do with it,
but what about that tomato smell? Our
perception of taste is enhanced by how food smells before we put it in our
mouths and as we chew it. The chemicals
that produce the tomato aroma are called volatiles. The food industry assumed that the volatiles
that are found in the highest concentrations are the ones that make a tomato a
tomato, and these should be the targets of genetic manipulation. A paper by Tieman et al, which appeared this
week in Current Biology, challenges this thinking by systematically
investigating what combination of chemicals found naturally in tomatoes makes a
delicious tomato.
Mass produced tomatoes are
relatively homogenous, so the authors decided to examine the chemical
composition of 152 heirloom varieties. I
think it’s worth noting the names of a few of these varieties: Bloody Butcher,
Giant Oxheart, Crimson Sprinter, Tasti-Lee, Mr. Stripey, and Mexico
Midget.
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| Bloody Butcher variety of heirloom tomato. (Credit: Totally Tomatoes) |
After figuring out the
concentration of chemicals in the tomatoes, the researchers asked consumers to
rate the flavor of the tomato varieties.
Surprisingly, a number of generic supermarket tomatoes scored quite
high. There was no simple pattern of
chemicals that defined a good tomato. As
you would expect, the flavor profile of a tomato is quite complex, but the
authors were able to pull out some new interesting information from their
analysis.
1) The volatiles that are
the most concentrated in tomatoes do not necessarily correlate with perceived
flavor intensity. In other words, some
of the odors that are in the highest concentrations are not associated with flavor
intensity. Take them or leave them,
either way the consumer wouldn’t notice.
The authors proved this by testing the flavor of mutant tomatoes that
cannot enzymatically produce some of the volatiles that are normally found in
high concentrations. There was no difference
in preference between the mutants and normal tomatoes.
2) Some of the volatiles
contributed to the perception of sweetness.
In particular, an odor called geranial was positively correlated with
sweetness. To investigate this further,
they used a mutant tomato that could not make geranial but still had the same
amount of sugars and acids. Consumers
rated these mutants as being less sweet even though the sugar:acid ratio was
exactly the same as the normal tomato.
Think about that for a minute... a smell increased the sweetness of a
food. We could replace excess sugars in
processed foods with geranial to lower the calories without affecting the
overall taste of the food!
So what makes a bloody
butcher tomato taste so good? High
levels of geranial and other volatiles that trick your taste perception into
thinking you’ve bitten into a slice of heaven.
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